Merge branch 'master' into fix-end2end-test
diff --git a/.pylintrc b/.pylintrc
index 05b4e68..453b45a 100644
--- a/.pylintrc
+++ b/.pylintrc
@@ -38,6 +38,9 @@
 	# TODO(https://github.com/grpc/grpc/issues/261): This doesn't seem to
 	# work for now? Try with a later pylint?
 	locally-disabled,
+	# NOTE(nathaniel): What even is this? *Enabling* an inspection results
+	# in a warning? How does that encourage more analysis and coverage?
+	locally-enabled,
 	# NOTE(nathaniel): We don't write doc strings for most private code
 	# elements.
 	missing-docstring,
diff --git a/BUILD b/BUILD
index 6b49973..49c340d 100644
--- a/BUILD
+++ b/BUILD
@@ -593,6 +593,9 @@
         "src/core/lib/iomgr/ev_windows.c",
         "src/core/lib/iomgr/exec_ctx.c",
         "src/core/lib/iomgr/executor.c",
+        "src/core/lib/iomgr/gethostname_host_name_max.c",
+        "src/core/lib/iomgr/gethostname_sysconf.c",
+        "src/core/lib/iomgr/gethostname_fallback.c",
         "src/core/lib/iomgr/iocp_windows.c",
         "src/core/lib/iomgr/iomgr.c",
         "src/core/lib/iomgr/iomgr_posix.c",
@@ -718,6 +721,7 @@
         "src/core/lib/iomgr/ev_posix.h",
         "src/core/lib/iomgr/exec_ctx.h",
         "src/core/lib/iomgr/executor.h",
+        "src/core/lib/iomgr/gethostname.h",
         "src/core/lib/iomgr/iocp_windows.h",
         "src/core/lib/iomgr/iomgr.h",
         "src/core/lib/iomgr/iomgr_internal.h",
@@ -774,6 +778,7 @@
         "src/core/lib/slice/slice_hash_table.h",
         "src/core/lib/slice/slice_internal.h",
         "src/core/lib/slice/slice_string_helpers.h",
+        "src/core/lib/surface/alarm_internal.h",
         "src/core/lib/surface/api_trace.h",
         "src/core/lib/surface/call.h",
         "src/core/lib/surface/call_test_only.h",
@@ -1407,31 +1412,45 @@
 )
 
 grpc_cc_library(
+    name = "tsi_interface",
+    srcs = [
+        "src/core/tsi/transport_security.c",
+        "src/core/tsi/transport_security_adapter.c",
+    ],
+    hdrs = [
+        "src/core/tsi/transport_security.h",
+        "src/core/tsi/transport_security_adapter.h",
+        "src/core/tsi/transport_security_interface.h",
+    ],
+    language = "c",
+    deps = [
+        "gpr",
+        "grpc_trace",
+    ],
+)
+
+grpc_cc_library(
     name = "tsi",
     srcs = [
         "src/core/tsi/fake_transport_security.c",
         "src/core/tsi/gts_transport_security.c",
         "src/core/tsi/ssl_transport_security.c",
-        "src/core/tsi/transport_security.c",
-        "src/core/tsi/transport_security_adapter.c",
+        "src/core/tsi/transport_security_grpc.c",
     ],
     hdrs = [
         "src/core/tsi/fake_transport_security.h",
         "src/core/tsi/gts_transport_security.h",
         "src/core/tsi/ssl_transport_security.h",
         "src/core/tsi/ssl_types.h",
-        "src/core/tsi/transport_security.h",
-        "src/core/tsi/transport_security_adapter.h",
-        "src/core/tsi/transport_security_interface.h",
+        "src/core/tsi/transport_security_grpc.h",
     ],
     external_deps = [
         "libssl",
     ],
     language = "c",
     deps = [
-        "gpr",
         "grpc_base",
-        "grpc_trace",
+        "tsi_interface",
     ],
 )
 
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 6e1b471..8dc4758 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -978,6 +978,9 @@
   src/core/lib/iomgr/ev_windows.c
   src/core/lib/iomgr/exec_ctx.c
   src/core/lib/iomgr/executor.c
+  src/core/lib/iomgr/gethostname_fallback.c
+  src/core/lib/iomgr/gethostname_host_name_max.c
+  src/core/lib/iomgr/gethostname_sysconf.c
   src/core/lib/iomgr/iocp_windows.c
   src/core/lib/iomgr/iomgr.c
   src/core/lib/iomgr/iomgr_posix.c
@@ -1129,6 +1132,7 @@
   src/core/tsi/fake_transport_security.c
   src/core/tsi/gts_transport_security.c
   src/core/tsi/ssl_transport_security.c
+  src/core/tsi/transport_security_grpc.c
   src/core/tsi/transport_security.c
   src/core/tsi/transport_security_adapter.c
   src/core/ext/transport/chttp2/server/chttp2_server.c
@@ -1322,6 +1326,9 @@
   src/core/lib/iomgr/ev_windows.c
   src/core/lib/iomgr/exec_ctx.c
   src/core/lib/iomgr/executor.c
+  src/core/lib/iomgr/gethostname_fallback.c
+  src/core/lib/iomgr/gethostname_host_name_max.c
+  src/core/lib/iomgr/gethostname_sysconf.c
   src/core/lib/iomgr/iocp_windows.c
   src/core/lib/iomgr/iomgr.c
   src/core/lib/iomgr/iomgr_posix.c
@@ -1497,6 +1504,7 @@
   src/core/tsi/fake_transport_security.c
   src/core/tsi/gts_transport_security.c
   src/core/tsi/ssl_transport_security.c
+  src/core/tsi/transport_security_grpc.c
   src/core/tsi/transport_security.c
   src/core/tsi/transport_security_adapter.c
   src/core/ext/transport/chttp2/client/chttp2_connector.c
@@ -1634,6 +1642,9 @@
   src/core/lib/iomgr/ev_windows.c
   src/core/lib/iomgr/exec_ctx.c
   src/core/lib/iomgr/executor.c
+  src/core/lib/iomgr/gethostname_fallback.c
+  src/core/lib/iomgr/gethostname_host_name_max.c
+  src/core/lib/iomgr/gethostname_sysconf.c
   src/core/lib/iomgr/iocp_windows.c
   src/core/lib/iomgr/iomgr.c
   src/core/lib/iomgr/iomgr_posix.c
@@ -1891,6 +1902,9 @@
   src/core/lib/iomgr/ev_windows.c
   src/core/lib/iomgr/exec_ctx.c
   src/core/lib/iomgr/executor.c
+  src/core/lib/iomgr/gethostname_fallback.c
+  src/core/lib/iomgr/gethostname_host_name_max.c
+  src/core/lib/iomgr/gethostname_sysconf.c
   src/core/lib/iomgr/iocp_windows.c
   src/core/lib/iomgr/iomgr.c
   src/core/lib/iomgr/iomgr_posix.c
@@ -2134,6 +2148,9 @@
   src/core/lib/iomgr/ev_windows.c
   src/core/lib/iomgr/exec_ctx.c
   src/core/lib/iomgr/executor.c
+  src/core/lib/iomgr/gethostname_fallback.c
+  src/core/lib/iomgr/gethostname_host_name_max.c
+  src/core/lib/iomgr/gethostname_sysconf.c
   src/core/lib/iomgr/iocp_windows.c
   src/core/lib/iomgr/iomgr.c
   src/core/lib/iomgr/iomgr_posix.c
@@ -2827,6 +2844,9 @@
   src/core/lib/iomgr/ev_windows.c
   src/core/lib/iomgr/exec_ctx.c
   src/core/lib/iomgr/executor.c
+  src/core/lib/iomgr/gethostname_fallback.c
+  src/core/lib/iomgr/gethostname_host_name_max.c
+  src/core/lib/iomgr/gethostname_sysconf.c
   src/core/lib/iomgr/iocp_windows.c
   src/core/lib/iomgr/iomgr.c
   src/core/lib/iomgr/iomgr_posix.c
diff --git a/Makefile b/Makefile
index 5168b30..74f05f5 100644
--- a/Makefile
+++ b/Makefile
@@ -2925,6 +2925,9 @@
     src/core/lib/iomgr/ev_windows.c \
     src/core/lib/iomgr/exec_ctx.c \
     src/core/lib/iomgr/executor.c \
+    src/core/lib/iomgr/gethostname_fallback.c \
+    src/core/lib/iomgr/gethostname_host_name_max.c \
+    src/core/lib/iomgr/gethostname_sysconf.c \
     src/core/lib/iomgr/iocp_windows.c \
     src/core/lib/iomgr/iomgr.c \
     src/core/lib/iomgr/iomgr_posix.c \
@@ -3076,6 +3079,7 @@
     src/core/tsi/fake_transport_security.c \
     src/core/tsi/gts_transport_security.c \
     src/core/tsi/ssl_transport_security.c \
+    src/core/tsi/transport_security_grpc.c \
     src/core/tsi/transport_security.c \
     src/core/tsi/transport_security_adapter.c \
     src/core/ext/transport/chttp2/server/chttp2_server.c \
@@ -3267,6 +3271,9 @@
     src/core/lib/iomgr/ev_windows.c \
     src/core/lib/iomgr/exec_ctx.c \
     src/core/lib/iomgr/executor.c \
+    src/core/lib/iomgr/gethostname_fallback.c \
+    src/core/lib/iomgr/gethostname_host_name_max.c \
+    src/core/lib/iomgr/gethostname_sysconf.c \
     src/core/lib/iomgr/iocp_windows.c \
     src/core/lib/iomgr/iomgr.c \
     src/core/lib/iomgr/iomgr_posix.c \
@@ -3442,6 +3449,7 @@
     src/core/tsi/fake_transport_security.c \
     src/core/tsi/gts_transport_security.c \
     src/core/tsi/ssl_transport_security.c \
+    src/core/tsi/transport_security_grpc.c \
     src/core/tsi/transport_security.c \
     src/core/tsi/transport_security_adapter.c \
     src/core/ext/transport/chttp2/client/chttp2_connector.c \
@@ -3576,6 +3584,9 @@
     src/core/lib/iomgr/ev_windows.c \
     src/core/lib/iomgr/exec_ctx.c \
     src/core/lib/iomgr/executor.c \
+    src/core/lib/iomgr/gethostname_fallback.c \
+    src/core/lib/iomgr/gethostname_host_name_max.c \
+    src/core/lib/iomgr/gethostname_sysconf.c \
     src/core/lib/iomgr/iocp_windows.c \
     src/core/lib/iomgr/iomgr.c \
     src/core/lib/iomgr/iomgr_posix.c \
@@ -3822,6 +3833,9 @@
     src/core/lib/iomgr/ev_windows.c \
     src/core/lib/iomgr/exec_ctx.c \
     src/core/lib/iomgr/executor.c \
+    src/core/lib/iomgr/gethostname_fallback.c \
+    src/core/lib/iomgr/gethostname_host_name_max.c \
+    src/core/lib/iomgr/gethostname_sysconf.c \
     src/core/lib/iomgr/iocp_windows.c \
     src/core/lib/iomgr/iomgr.c \
     src/core/lib/iomgr/iomgr_posix.c \
@@ -4041,6 +4055,9 @@
     src/core/lib/iomgr/ev_windows.c \
     src/core/lib/iomgr/exec_ctx.c \
     src/core/lib/iomgr/executor.c \
+    src/core/lib/iomgr/gethostname_fallback.c \
+    src/core/lib/iomgr/gethostname_host_name_max.c \
+    src/core/lib/iomgr/gethostname_sysconf.c \
     src/core/lib/iomgr/iocp_windows.c \
     src/core/lib/iomgr/iomgr.c \
     src/core/lib/iomgr/iomgr_posix.c \
@@ -4717,6 +4734,9 @@
     src/core/lib/iomgr/ev_windows.c \
     src/core/lib/iomgr/exec_ctx.c \
     src/core/lib/iomgr/executor.c \
+    src/core/lib/iomgr/gethostname_fallback.c \
+    src/core/lib/iomgr/gethostname_host_name_max.c \
+    src/core/lib/iomgr/gethostname_sysconf.c \
     src/core/lib/iomgr/iocp_windows.c \
     src/core/lib/iomgr/iomgr.c \
     src/core/lib/iomgr/iomgr_posix.c \
@@ -19703,6 +19723,7 @@
 src/core/tsi/ssl_transport_security.c: $(OPENSSL_DEP)
 src/core/tsi/transport_security.c: $(OPENSSL_DEP)
 src/core/tsi/transport_security_adapter.c: $(OPENSSL_DEP)
+src/core/tsi/transport_security_grpc.c: $(OPENSSL_DEP)
 src/cpp/client/cronet_credentials.cc: $(OPENSSL_DEP)
 src/cpp/client/secure_credentials.cc: $(OPENSSL_DEP)
 src/cpp/common/auth_property_iterator.cc: $(OPENSSL_DEP)
diff --git a/binding.gyp b/binding.gyp
index 8a2900b..bbefd05 100644
--- a/binding.gyp
+++ b/binding.gyp
@@ -687,6 +687,9 @@
         'src/core/lib/iomgr/ev_windows.c',
         'src/core/lib/iomgr/exec_ctx.c',
         'src/core/lib/iomgr/executor.c',
+        'src/core/lib/iomgr/gethostname_fallback.c',
+        'src/core/lib/iomgr/gethostname_host_name_max.c',
+        'src/core/lib/iomgr/gethostname_sysconf.c',
         'src/core/lib/iomgr/iocp_windows.c',
         'src/core/lib/iomgr/iomgr.c',
         'src/core/lib/iomgr/iomgr_posix.c',
@@ -838,6 +841,7 @@
         'src/core/tsi/fake_transport_security.c',
         'src/core/tsi/gts_transport_security.c',
         'src/core/tsi/ssl_transport_security.c',
+        'src/core/tsi/transport_security_grpc.c',
         'src/core/tsi/transport_security.c',
         'src/core/tsi/transport_security_adapter.c',
         'src/core/ext/transport/chttp2/server/chttp2_server.c',
diff --git a/build.yaml b/build.yaml
index 81bcf44..a459b9d 100644
--- a/build.yaml
+++ b/build.yaml
@@ -214,6 +214,9 @@
   - src/core/lib/iomgr/ev_windows.c
   - src/core/lib/iomgr/exec_ctx.c
   - src/core/lib/iomgr/executor.c
+  - src/core/lib/iomgr/gethostname_fallback.c
+  - src/core/lib/iomgr/gethostname_host_name_max.c
+  - src/core/lib/iomgr/gethostname_sysconf.c
   - src/core/lib/iomgr/iocp_windows.c
   - src/core/lib/iomgr/iomgr.c
   - src/core/lib/iomgr/iomgr_posix.c
@@ -359,6 +362,7 @@
   - src/core/lib/iomgr/ev_posix.h
   - src/core/lib/iomgr/exec_ctx.h
   - src/core/lib/iomgr/executor.h
+  - src/core/lib/iomgr/gethostname.h
   - src/core/lib/iomgr/iocp_windows.h
   - src/core/lib/iomgr/iomgr.h
   - src/core/lib/iomgr/iomgr_internal.h
@@ -415,6 +419,7 @@
   - src/core/lib/slice/slice_hash_table.h
   - src/core/lib/slice/slice_internal.h
   - src/core/lib/slice/slice_string_helpers.h
+  - src/core/lib/surface/alarm_internal.h
   - src/core/lib/surface/api_trace.h
   - src/core/lib/surface/call.h
   - src/core/lib/surface/call_test_only.h
@@ -920,22 +925,33 @@
   - src/core/tsi/gts_transport_security.h
   - src/core/tsi/ssl_transport_security.h
   - src/core/tsi/ssl_types.h
-  - src/core/tsi/transport_security.h
-  - src/core/tsi/transport_security_adapter.h
-  - src/core/tsi/transport_security_interface.h
+  - src/core/tsi/transport_security_grpc.h
   src:
   - src/core/tsi/fake_transport_security.c
   - src/core/tsi/gts_transport_security.c
   - src/core/tsi/ssl_transport_security.c
-  - src/core/tsi/transport_security.c
-  - src/core/tsi/transport_security_adapter.c
+  - src/core/tsi/transport_security_grpc.c
   deps:
   - gpr
   plugin: grpc_tsi_gts
   secure: true
   uses:
-  - grpc_trace
+  - tsi_interface
   - grpc_base
+  - grpc_trace
+- name: tsi_interface
+  headers:
+  - src/core/tsi/transport_security.h
+  - src/core/tsi/transport_security_adapter.h
+  - src/core/tsi/transport_security_interface.h
+  src:
+  - src/core/tsi/transport_security.c
+  - src/core/tsi/transport_security_adapter.c
+  deps:
+  - gpr
+  secure: true
+  uses:
+  - grpc_trace
 - name: grpc++_codegen_base
   language: c++
   public_headers:
diff --git a/config.m4 b/config.m4
index c5332f1..f6f8531 100644
--- a/config.m4
+++ b/config.m4
@@ -116,6 +116,9 @@
     src/core/lib/iomgr/ev_windows.c \
     src/core/lib/iomgr/exec_ctx.c \
     src/core/lib/iomgr/executor.c \
+    src/core/lib/iomgr/gethostname_fallback.c \
+    src/core/lib/iomgr/gethostname_host_name_max.c \
+    src/core/lib/iomgr/gethostname_sysconf.c \
     src/core/lib/iomgr/iocp_windows.c \
     src/core/lib/iomgr/iomgr.c \
     src/core/lib/iomgr/iomgr_posix.c \
@@ -267,6 +270,7 @@
     src/core/tsi/fake_transport_security.c \
     src/core/tsi/gts_transport_security.c \
     src/core/tsi/ssl_transport_security.c \
+    src/core/tsi/transport_security_grpc.c \
     src/core/tsi/transport_security.c \
     src/core/tsi/transport_security_adapter.c \
     src/core/ext/transport/chttp2/server/chttp2_server.c \
diff --git a/config.w32 b/config.w32
index 8529bd5..1d1a0a4 100644
--- a/config.w32
+++ b/config.w32
@@ -93,6 +93,9 @@
     "src\\core\\lib\\iomgr\\ev_windows.c " +
     "src\\core\\lib\\iomgr\\exec_ctx.c " +
     "src\\core\\lib\\iomgr\\executor.c " +
+    "src\\core\\lib\\iomgr\\gethostname_fallback.c " +
+    "src\\core\\lib\\iomgr\\gethostname_host_name_max.c " +
+    "src\\core\\lib\\iomgr\\gethostname_sysconf.c " +
     "src\\core\\lib\\iomgr\\iocp_windows.c " +
     "src\\core\\lib\\iomgr\\iomgr.c " +
     "src\\core\\lib\\iomgr\\iomgr_posix.c " +
@@ -244,6 +247,7 @@
     "src\\core\\tsi\\fake_transport_security.c " +
     "src\\core\\tsi\\gts_transport_security.c " +
     "src\\core\\tsi\\ssl_transport_security.c " +
+    "src\\core\\tsi\\transport_security_grpc.c " +
     "src\\core\\tsi\\transport_security.c " +
     "src\\core\\tsi\\transport_security_adapter.c " +
     "src\\core\\ext\\transport\\chttp2\\server\\chttp2_server.c " +
diff --git a/doc/environment_variables.md b/doc/environment_variables.md
index 036824d..a2cde92 100644
--- a/doc/environment_variables.md
+++ b/doc/environment_variables.md
@@ -69,6 +69,7 @@
 
   The following tracers will only run in binaries built in DEBUG mode. This is
   accomplished by invoking `CONFIG=dbg make <target>`
+  - alarm_refcount - refcounting traces for grpc_alarm structure
   - metadata - tracks creation and mutation of metadata
   - closure - tracks closure creation, scheduling, and completion
   - pending_tags - traces still-in-progress tags on completion queues
diff --git a/doc/epoll-polling-engine.md b/doc/epoll-polling-engine.md
index ab7030a..1f5d855 100644
--- a/doc/epoll-polling-engine.md
+++ b/doc/epoll-polling-engine.md
@@ -5,7 +5,7 @@
 
 > Status: As of June 2016, this change is implemented and merged.
 
-> * The bulk of the functionality is in: [ev_poll_linux.c](https://github.com/grpc/grpc/blob/master/src/core/lib/iomgr/ev_epoll_linux.c)
+> * The bulk of the functionality is in: [ev_epollsig_linux.c](https://github.com/grpc/grpc/blob/master/src/core/lib/iomgr/ev_epollsig_linux.c)
 > * Pull request: https://github.com/grpc/grpc/pull/6803
 
 ## 1. Introduction
diff --git a/doc/load-balancing.md b/doc/load-balancing.md
index f56d2b0..88ff354 100644
--- a/doc/load-balancing.md
+++ b/doc/load-balancing.md
@@ -113,8 +113,8 @@
    that indicates which client-side load-balancing policy to use (e.g.,
    `round_robin` or `grpclb`).
 2. The client instantiates the load balancing policy.
-   - Note: If all addresses returned by the resolver are balancer
-     addresses, then the client will use the `grpclb` policy, regardless
+   - Note: If any one of the addresses returned by the resolver is a balancer
+     address, then the client will use the `grpclb` policy, regardless
      of what load-balancing policy was requested by the service config.
      Otherwise, the client will use the load-balancing policy requested
      by the service config.  If no load-balancing policy is requested
diff --git a/gRPC-Core.podspec b/gRPC-Core.podspec
index 11422f5..4b1a8f3 100644
--- a/gRPC-Core.podspec
+++ b/gRPC-Core.podspec
@@ -290,6 +290,7 @@
                       'src/core/tsi/gts_transport_security.h',
                       'src/core/tsi/ssl_transport_security.h',
                       'src/core/tsi/ssl_types.h',
+                      'src/core/tsi/transport_security_grpc.h',
                       'src/core/tsi/transport_security.h',
                       'src/core/tsi/transport_security_adapter.h',
                       'src/core/tsi/transport_security_interface.h',
@@ -344,6 +345,7 @@
                       'src/core/lib/iomgr/ev_posix.h',
                       'src/core/lib/iomgr/exec_ctx.h',
                       'src/core/lib/iomgr/executor.h',
+                      'src/core/lib/iomgr/gethostname.h',
                       'src/core/lib/iomgr/iocp_windows.h',
                       'src/core/lib/iomgr/iomgr.h',
                       'src/core/lib/iomgr/iomgr_internal.h',
@@ -400,6 +402,7 @@
                       'src/core/lib/slice/slice_hash_table.h',
                       'src/core/lib/slice/slice_internal.h',
                       'src/core/lib/slice/slice_string_helpers.h',
+                      'src/core/lib/surface/alarm_internal.h',
                       'src/core/lib/surface/api_trace.h',
                       'src/core/lib/surface/call.h',
                       'src/core/lib/surface/call_test_only.h',
@@ -492,6 +495,9 @@
                       'src/core/lib/iomgr/ev_windows.c',
                       'src/core/lib/iomgr/exec_ctx.c',
                       'src/core/lib/iomgr/executor.c',
+                      'src/core/lib/iomgr/gethostname_fallback.c',
+                      'src/core/lib/iomgr/gethostname_host_name_max.c',
+                      'src/core/lib/iomgr/gethostname_sysconf.c',
                       'src/core/lib/iomgr/iocp_windows.c',
                       'src/core/lib/iomgr/iomgr.c',
                       'src/core/lib/iomgr/iomgr_posix.c',
@@ -643,6 +649,7 @@
                       'src/core/tsi/fake_transport_security.c',
                       'src/core/tsi/gts_transport_security.c',
                       'src/core/tsi/ssl_transport_security.c',
+                      'src/core/tsi/transport_security_grpc.c',
                       'src/core/tsi/transport_security.c',
                       'src/core/tsi/transport_security_adapter.c',
                       'src/core/ext/transport/chttp2/server/chttp2_server.c',
@@ -777,6 +784,7 @@
                               'src/core/tsi/gts_transport_security.h',
                               'src/core/tsi/ssl_transport_security.h',
                               'src/core/tsi/ssl_types.h',
+                              'src/core/tsi/transport_security_grpc.h',
                               'src/core/tsi/transport_security.h',
                               'src/core/tsi/transport_security_adapter.h',
                               'src/core/tsi/transport_security_interface.h',
@@ -831,6 +839,7 @@
                               'src/core/lib/iomgr/ev_posix.h',
                               'src/core/lib/iomgr/exec_ctx.h',
                               'src/core/lib/iomgr/executor.h',
+                              'src/core/lib/iomgr/gethostname.h',
                               'src/core/lib/iomgr/iocp_windows.h',
                               'src/core/lib/iomgr/iomgr.h',
                               'src/core/lib/iomgr/iomgr_internal.h',
@@ -887,6 +896,7 @@
                               'src/core/lib/slice/slice_hash_table.h',
                               'src/core/lib/slice/slice_internal.h',
                               'src/core/lib/slice/slice_string_helpers.h',
+                              'src/core/lib/surface/alarm_internal.h',
                               'src/core/lib/surface/api_trace.h',
                               'src/core/lib/surface/call.h',
                               'src/core/lib/surface/call_test_only.h',
diff --git a/grpc.gemspec b/grpc.gemspec
old mode 100755
new mode 100644
index a456667..f04a141
--- a/grpc.gemspec
+++ b/grpc.gemspec
@@ -222,6 +222,7 @@
   s.files += %w( src/core/tsi/gts_transport_security.h )
   s.files += %w( src/core/tsi/ssl_transport_security.h )
   s.files += %w( src/core/tsi/ssl_types.h )
+  s.files += %w( src/core/tsi/transport_security_grpc.h )
   s.files += %w( src/core/tsi/transport_security.h )
   s.files += %w( src/core/tsi/transport_security_adapter.h )
   s.files += %w( src/core/tsi/transport_security_interface.h )
@@ -276,6 +277,7 @@
   s.files += %w( src/core/lib/iomgr/ev_posix.h )
   s.files += %w( src/core/lib/iomgr/exec_ctx.h )
   s.files += %w( src/core/lib/iomgr/executor.h )
+  s.files += %w( src/core/lib/iomgr/gethostname.h )
   s.files += %w( src/core/lib/iomgr/iocp_windows.h )
   s.files += %w( src/core/lib/iomgr/iomgr.h )
   s.files += %w( src/core/lib/iomgr/iomgr_internal.h )
@@ -332,6 +334,7 @@
   s.files += %w( src/core/lib/slice/slice_hash_table.h )
   s.files += %w( src/core/lib/slice/slice_internal.h )
   s.files += %w( src/core/lib/slice/slice_string_helpers.h )
+  s.files += %w( src/core/lib/surface/alarm_internal.h )
   s.files += %w( src/core/lib/surface/api_trace.h )
   s.files += %w( src/core/lib/surface/call.h )
   s.files += %w( src/core/lib/surface/call_test_only.h )
@@ -424,6 +427,9 @@
   s.files += %w( src/core/lib/iomgr/ev_windows.c )
   s.files += %w( src/core/lib/iomgr/exec_ctx.c )
   s.files += %w( src/core/lib/iomgr/executor.c )
+  s.files += %w( src/core/lib/iomgr/gethostname_fallback.c )
+  s.files += %w( src/core/lib/iomgr/gethostname_host_name_max.c )
+  s.files += %w( src/core/lib/iomgr/gethostname_sysconf.c )
   s.files += %w( src/core/lib/iomgr/iocp_windows.c )
   s.files += %w( src/core/lib/iomgr/iomgr.c )
   s.files += %w( src/core/lib/iomgr/iomgr_posix.c )
@@ -575,6 +581,7 @@
   s.files += %w( src/core/tsi/fake_transport_security.c )
   s.files += %w( src/core/tsi/gts_transport_security.c )
   s.files += %w( src/core/tsi/ssl_transport_security.c )
+  s.files += %w( src/core/tsi/transport_security_grpc.c )
   s.files += %w( src/core/tsi/transport_security.c )
   s.files += %w( src/core/tsi/transport_security_adapter.c )
   s.files += %w( src/core/ext/transport/chttp2/server/chttp2_server.c )
diff --git a/include/grpc++/impl/codegen/call.h b/include/grpc++/impl/codegen/call.h
index f6eefb9..33d8f4c 100644
--- a/include/grpc++/impl/codegen/call.h
+++ b/include/grpc++/impl/codegen/call.h
@@ -349,6 +349,28 @@
   bool allow_not_getting_message_;
 };
 
+namespace CallOpGenericRecvMessageHelper {
+class DeserializeFunc {
+ public:
+  virtual Status Deserialize(grpc_byte_buffer* buf) = 0;
+  virtual ~DeserializeFunc() {}
+};
+
+template <class R>
+class DeserializeFuncType final : public DeserializeFunc {
+ public:
+  DeserializeFuncType(R* message) : message_(message) {}
+  Status Deserialize(grpc_byte_buffer* buf) override {
+    return SerializationTraits<R>::Deserialize(buf, message_);
+  }
+
+  ~DeserializeFuncType() override {}
+
+ private:
+  R* message_;  // Not a managed pointer because management is external to this
+};
+}  // namespace CallOpGenericRecvMessageHelper
+
 class CallOpGenericRecvMessage {
  public:
   CallOpGenericRecvMessage()
@@ -356,9 +378,11 @@
 
   template <class R>
   void RecvMessage(R* message) {
-    deserialize_ = [message](grpc_byte_buffer* buf) -> Status {
-      return SerializationTraits<R>::Deserialize(buf, message);
-    };
+    // Use an explicit base class pointer to avoid resolution error in the
+    // following unique_ptr::reset for some old implementations.
+    CallOpGenericRecvMessageHelper::DeserializeFunc* func =
+        new CallOpGenericRecvMessageHelper::DeserializeFuncType<R>(message);
+    deserialize_.reset(func);
   }
 
   // Do not change status if no message is received.
@@ -381,7 +405,7 @@
     if (recv_buf_) {
       if (*status) {
         got_message = true;
-        *status = deserialize_(recv_buf_).ok();
+        *status = deserialize_->Deserialize(recv_buf_).ok();
       } else {
         got_message = false;
         g_core_codegen_interface->grpc_byte_buffer_destroy(recv_buf_);
@@ -392,12 +416,11 @@
         *status = false;
       }
     }
-    deserialize_ = DeserializeFunc();
+    deserialize_.reset();
   }
 
  private:
-  typedef std::function<Status(grpc_byte_buffer*)> DeserializeFunc;
-  DeserializeFunc deserialize_;
+  std::unique_ptr<CallOpGenericRecvMessageHelper::DeserializeFunc> deserialize_;
   grpc_byte_buffer* recv_buf_;
   bool allow_not_getting_message_;
 };
diff --git a/include/grpc++/support/slice.h b/include/grpc++/support/slice.h
index 0b4ba7c..bbf97f2 100644
--- a/include/grpc++/support/slice.h
+++ b/include/grpc++/support/slice.h
@@ -67,6 +67,20 @@
     return *this;
   }
 
+  /// Create a slice pointing at some data. Calls malloc to allocate a refcount
+  /// for the object, and arranges that destroy will be called with the
+  /// user data pointer passed in at destruction. Can be the same as buf or
+  /// different (e.g., if data is part of a larger structure that must be
+  /// destroyed when the data is no longer needed)
+  Slice(void* buf, size_t len, void (*destroy)(void*), void* user_data);
+
+  /// Specialization of above for common case where buf == user_data
+  Slice(void* buf, size_t len, void (*destroy)(void*))
+      : Slice(buf, len, destroy, buf) {}
+
+  /// Similar to the above but has a destroy that also takes slice length
+  Slice(void* buf, size_t len, void (*destroy)(void*, size_t));
+
   /// Byte size.
   size_t size() const { return GRPC_SLICE_LENGTH(slice_); }
 
diff --git a/include/grpc/impl/codegen/byte_buffer_reader.h b/include/grpc/impl/codegen/byte_buffer_reader.h
index 2ae3f1e..dc0f154 100644
--- a/include/grpc/impl/codegen/byte_buffer_reader.h
+++ b/include/grpc/impl/codegen/byte_buffer_reader.h
@@ -29,7 +29,7 @@
   struct grpc_byte_buffer *buffer_in;
   struct grpc_byte_buffer *buffer_out;
   /** Different current objects correspond to different types of byte buffers */
-  union {
+  union grpc_byte_buffer_reader_current {
     /** Index into a slice buffer's array of slices */
     unsigned index;
   } current;
diff --git a/include/grpc/impl/codegen/compression_types.h b/include/grpc/impl/codegen/compression_types.h
index e39c13e..f1b2de3 100644
--- a/include/grpc/impl/codegen/compression_types.h
+++ b/include/grpc/impl/codegen/compression_types.h
@@ -84,7 +84,7 @@
    * behind \a GRPC_COMPRESSION_CHANNEL_DEFAULT_LEVEL. If present, takes
    * precedence over \a default_algorithm.
    * TODO(dgq): currently only available for server channels. */
-  struct {
+  struct grpc_compression_options_default_level {
     int is_set;
     grpc_compression_level level;
   } default_level;
@@ -92,7 +92,7 @@
   /** The default channel compression algorithm. It'll be used in the absence of
    * call specific settings. This option corresponds to the channel argument key
    * behind \a GRPC_COMPRESSION_CHANNEL_DEFAULT_ALGORITHM. */
-  struct {
+  struct grpc_compression_options_default_algorithm {
     int is_set;
     grpc_compression_algorithm algorithm;
   } default_algorithm;
diff --git a/include/grpc/impl/codegen/grpc_types.h b/include/grpc/impl/codegen/grpc_types.h
index bb3c90e..8813ec8 100644
--- a/include/grpc/impl/codegen/grpc_types.h
+++ b/include/grpc/impl/codegen/grpc_types.h
@@ -41,11 +41,11 @@
 typedef struct grpc_byte_buffer {
   void *reserved;
   grpc_byte_buffer_type type;
-  union {
-    struct {
+  union grpc_byte_buffer_data {
+    struct /* internal */ {
       void *reserved[8];
     } reserved;
-    struct {
+    struct grpc_compressed_buffer {
       grpc_compression_algorithm compression;
       grpc_slice_buffer slice_buffer;
     } raw;
@@ -104,10 +104,10 @@
 typedef struct {
   grpc_arg_type type;
   char *key;
-  union {
+  union grpc_arg_value {
     char *string;
     int integer;
-    struct {
+    struct grpc_arg_pointer {
       void *p;
       const grpc_arg_pointer_vtable *vtable;
     } pointer;
@@ -258,8 +258,12 @@
 #define GRPC_ARG_RESOURCE_QUOTA "grpc.resource_quota"
 /** If non-zero, expand wildcard addresses to a list of local addresses. */
 #define GRPC_ARG_EXPAND_WILDCARD_ADDRS "grpc.expand_wildcard_addrs"
-/** Service config data in JSON form. Not intended for use outside of tests. */
+/** Service config data in JSON form.
+    This value will be ignored if the name resolver returns a service config. */
 #define GRPC_ARG_SERVICE_CONFIG "grpc.service_config"
+/** Disable looking up the service config via the name resolver. */
+#define GRPC_ARG_SERVICE_CONFIG_DISABLE_RESOLUTION \
+  "grpc.service_config_disable_resolution"
 /** LB policy name. */
 #define GRPC_ARG_LB_POLICY_NAME "grpc.lb_policy_name"
 /** The grpc_socket_mutator instance that set the socket options. A pointer. */
@@ -387,7 +391,7 @@
   /** The following fields are reserved for grpc internal use.
       There is no need to initialize them, and they will be set to garbage
       during calls to grpc. */
-  struct {
+  struct /* internal */ {
     void *obfuscated[4];
   } internal_data;
 } grpc_metadata;
@@ -487,25 +491,25 @@
   uint32_t flags;
   /** Reserved for future usage */
   void *reserved;
-  union {
+  union grpc_op_data {
     /** Reserved for future usage */
-    struct {
+    struct /* internal */ {
       void *reserved[8];
     } reserved;
-    struct {
+    struct grpc_op_send_initial_metadata {
       size_t count;
       grpc_metadata *metadata;
       /** If \a is_set, \a compression_level will be used for the call.
        * Otherwise, \a compression_level won't be considered */
-      struct {
+      struct grpc_op_send_initial_metadata_maybe_compression_level {
         uint8_t is_set;
         grpc_compression_level level;
       } maybe_compression_level;
     } send_initial_metadata;
-    struct {
+    struct grpc_op_send_message {
       struct grpc_byte_buffer *send_message;
     } send_message;
-    struct {
+    struct grpc_op_send_status_from_server {
       size_t trailing_metadata_count;
       grpc_metadata *trailing_metadata;
       grpc_status_code status;
@@ -519,16 +523,16 @@
         object, recv_initial_metadata->array is owned by the caller).
         After the operation completes, call grpc_metadata_array_destroy on this
         value, or reuse it in a future op. */
-    struct {
+    struct grpc_op_recv_initial_metadata {
       grpc_metadata_array *recv_initial_metadata;
     } recv_initial_metadata;
     /** ownership of the byte buffer is moved to the caller; the caller must
         call grpc_byte_buffer_destroy on this value, or reuse it in a future op.
        */
-    struct {
+    struct grpc_op_recv_message {
       struct grpc_byte_buffer **recv_message;
     } recv_message;
-    struct {
+    struct grpc_op_recv_status_on_client {
       /** ownership of the array is with the caller, but ownership of the
           elements stays with the call object (ie key, value members are owned
           by the call object, trailing_metadata->array is owned by the caller).
@@ -538,7 +542,7 @@
       grpc_status_code *status;
       grpc_slice *status_details;
     } recv_status_on_client;
-    struct {
+    struct grpc_op_recv_close_on_server {
       /** out argument, set to 1 if the call failed in any way (seen as a
           cancellation on the server), or 0 if the call succeeded */
       int *cancelled;
diff --git a/include/grpc/impl/codegen/slice.h b/include/grpc/impl/codegen/slice.h
index 5ec439e..a04c683 100644
--- a/include/grpc/impl/codegen/slice.h
+++ b/include/grpc/impl/codegen/slice.h
@@ -75,12 +75,12 @@
    of data that is copied by value. */
 struct grpc_slice {
   struct grpc_slice_refcount *refcount;
-  union {
-    struct {
+  union grpc_slice_data {
+    struct grpc_slice_refcounted {
       uint8_t *bytes;
       size_t length;
     } refcounted;
-    struct {
+    struct grpc_slice_inlined {
       uint8_t length;
       uint8_t bytes[GRPC_SLICE_INLINED_SIZE];
     } inlined;
diff --git a/package.xml b/package.xml
index 9bdebe3..4e288b3 100644
--- a/package.xml
+++ b/package.xml
@@ -236,6 +236,7 @@
     <file baseinstalldir="/" name="src/core/tsi/gts_transport_security.h" role="src" />
     <file baseinstalldir="/" name="src/core/tsi/ssl_transport_security.h" role="src" />
     <file baseinstalldir="/" name="src/core/tsi/ssl_types.h" role="src" />
+    <file baseinstalldir="/" name="src/core/tsi/transport_security_grpc.h" role="src" />
     <file baseinstalldir="/" name="src/core/tsi/transport_security.h" role="src" />
     <file baseinstalldir="/" name="src/core/tsi/transport_security_adapter.h" role="src" />
     <file baseinstalldir="/" name="src/core/tsi/transport_security_interface.h" role="src" />
@@ -290,6 +291,7 @@
     <file baseinstalldir="/" name="src/core/lib/iomgr/ev_posix.h" role="src" />
     <file baseinstalldir="/" name="src/core/lib/iomgr/exec_ctx.h" role="src" />
     <file baseinstalldir="/" name="src/core/lib/iomgr/executor.h" role="src" />
+    <file baseinstalldir="/" name="src/core/lib/iomgr/gethostname.h" role="src" />
     <file baseinstalldir="/" name="src/core/lib/iomgr/iocp_windows.h" role="src" />
     <file baseinstalldir="/" name="src/core/lib/iomgr/iomgr.h" role="src" />
     <file baseinstalldir="/" name="src/core/lib/iomgr/iomgr_internal.h" role="src" />
@@ -346,6 +348,7 @@
     <file baseinstalldir="/" name="src/core/lib/slice/slice_hash_table.h" role="src" />
     <file baseinstalldir="/" name="src/core/lib/slice/slice_internal.h" role="src" />
     <file baseinstalldir="/" name="src/core/lib/slice/slice_string_helpers.h" role="src" />
+    <file baseinstalldir="/" name="src/core/lib/surface/alarm_internal.h" role="src" />
     <file baseinstalldir="/" name="src/core/lib/surface/api_trace.h" role="src" />
     <file baseinstalldir="/" name="src/core/lib/surface/call.h" role="src" />
     <file baseinstalldir="/" name="src/core/lib/surface/call_test_only.h" role="src" />
@@ -438,6 +441,9 @@
     <file baseinstalldir="/" name="src/core/lib/iomgr/ev_windows.c" role="src" />
     <file baseinstalldir="/" name="src/core/lib/iomgr/exec_ctx.c" role="src" />
     <file baseinstalldir="/" name="src/core/lib/iomgr/executor.c" role="src" />
+    <file baseinstalldir="/" name="src/core/lib/iomgr/gethostname_fallback.c" role="src" />
+    <file baseinstalldir="/" name="src/core/lib/iomgr/gethostname_host_name_max.c" role="src" />
+    <file baseinstalldir="/" name="src/core/lib/iomgr/gethostname_sysconf.c" role="src" />
     <file baseinstalldir="/" name="src/core/lib/iomgr/iocp_windows.c" role="src" />
     <file baseinstalldir="/" name="src/core/lib/iomgr/iomgr.c" role="src" />
     <file baseinstalldir="/" name="src/core/lib/iomgr/iomgr_posix.c" role="src" />
@@ -589,6 +595,7 @@
     <file baseinstalldir="/" name="src/core/tsi/fake_transport_security.c" role="src" />
     <file baseinstalldir="/" name="src/core/tsi/gts_transport_security.c" role="src" />
     <file baseinstalldir="/" name="src/core/tsi/ssl_transport_security.c" role="src" />
+    <file baseinstalldir="/" name="src/core/tsi/transport_security_grpc.c" role="src" />
     <file baseinstalldir="/" name="src/core/tsi/transport_security.c" role="src" />
     <file baseinstalldir="/" name="src/core/tsi/transport_security_adapter.c" role="src" />
     <file baseinstalldir="/" name="src/core/ext/transport/chttp2/server/chttp2_server.c" role="src" />
diff --git a/src/core/ext/census/tracing.c b/src/core/ext/census/tracing.c
index 543a73c..823c681 100644
--- a/src/core/ext/census/tracing.c
+++ b/src/core/ext/census/tracing.c
@@ -21,7 +21,6 @@
 #include <grpc/census.h>
 #include <grpc/support/alloc.h>
 #include <grpc/support/log.h>
-#include <openssl/rand.h>
 #include "src/core/ext/census/mlog.h"
 
 void trace_start_span(const trace_span_context *span_ctxt,
diff --git a/src/core/ext/filters/client_channel/resolver/dns/c_ares/dns_resolver_ares.c b/src/core/ext/filters/client_channel/resolver/dns/c_ares/dns_resolver_ares.c
index 04a7852..f1480bb 100644
--- a/src/core/ext/filters/client_channel/resolver/dns/c_ares/dns_resolver_ares.c
+++ b/src/core/ext/filters/client_channel/resolver/dns/c_ares/dns_resolver_ares.c
@@ -19,7 +19,10 @@
 #include <grpc/support/port_platform.h>
 #if GRPC_ARES == 1 && !defined(GRPC_UV)
 
+#include <limits.h>
+#include <stdio.h>
 #include <string.h>
+#include <unistd.h>
 
 #include <grpc/support/alloc.h>
 #include <grpc/support/host_port.h>
@@ -31,11 +34,14 @@
 #include "src/core/ext/filters/client_channel/resolver_registry.h"
 #include "src/core/lib/channel/channel_args.h"
 #include "src/core/lib/iomgr/combiner.h"
+#include "src/core/lib/iomgr/gethostname.h"
 #include "src/core/lib/iomgr/resolve_address.h"
 #include "src/core/lib/iomgr/timer.h"
+#include "src/core/lib/json/json.h"
 #include "src/core/lib/support/backoff.h"
 #include "src/core/lib/support/env.h"
 #include "src/core/lib/support/string.h"
+#include "src/core/lib/transport/service_config.h"
 
 #define GRPC_DNS_MIN_CONNECT_TIMEOUT_SECONDS 1
 #define GRPC_DNS_INITIAL_CONNECT_BACKOFF_SECONDS 1
@@ -54,6 +60,8 @@
   char *default_port;
   /** channel args. */
   grpc_channel_args *channel_args;
+  /** whether to request the service config */
+  bool request_service_config;
   /** pollset_set to drive the name resolution process */
   grpc_pollset_set *interested_parties;
 
@@ -85,6 +93,8 @@
 
   /** currently resolving addresses */
   grpc_lb_addresses *lb_addresses;
+  /** currently resolving service config */
+  char *service_config_json;
 } ares_dns_resolver;
 
 static void dns_ares_destroy(grpc_exec_ctx *exec_ctx, grpc_resolver *r);
@@ -144,6 +154,77 @@
   GRPC_RESOLVER_UNREF(exec_ctx, &r->base, "retry-timer");
 }
 
+static bool value_in_json_array(grpc_json *array, const char *value) {
+  for (grpc_json *entry = array->child; entry != NULL; entry = entry->next) {
+    if (entry->type == GRPC_JSON_STRING && strcmp(entry->value, value) == 0) {
+      return true;
+    }
+  }
+  return false;
+}
+
+static char *choose_service_config(char *service_config_choice_json) {
+  grpc_json *choices_json = grpc_json_parse_string(service_config_choice_json);
+  if (choices_json == NULL || choices_json->type != GRPC_JSON_ARRAY) {
+    gpr_log(GPR_ERROR, "cannot parse service config JSON string");
+    return NULL;
+  }
+  char *service_config = NULL;
+  for (grpc_json *choice = choices_json->child; choice != NULL;
+       choice = choice->next) {
+    if (choice->type != GRPC_JSON_OBJECT) {
+      gpr_log(GPR_ERROR, "cannot parse service config JSON string");
+      break;
+    }
+    grpc_json *service_config_json = NULL;
+    for (grpc_json *field = choice->child; field != NULL; field = field->next) {
+      // Check client language, if specified.
+      if (strcmp(field->key, "clientLanguage") == 0) {
+        if (field->type != GRPC_JSON_ARRAY ||
+            !value_in_json_array(field, "c++")) {
+          service_config_json = NULL;
+          break;
+        }
+      }
+      // Check client hostname, if specified.
+      if (strcmp(field->key, "clientHostname") == 0) {
+        char *hostname = grpc_gethostname();
+        if (hostname == NULL || field->type != GRPC_JSON_ARRAY ||
+            !value_in_json_array(field, hostname)) {
+          service_config_json = NULL;
+          break;
+        }
+      }
+      // Check percentage, if specified.
+      if (strcmp(field->key, "percentage") == 0) {
+        if (field->type != GRPC_JSON_NUMBER) {
+          service_config_json = NULL;
+          break;
+        }
+        int random_pct = rand() % 100;
+        int percentage;
+        if (sscanf(field->value, "%d", &percentage) != 1 ||
+            random_pct > percentage) {
+          service_config_json = NULL;
+          break;
+        }
+      }
+      // Save service config.
+      if (strcmp(field->key, "serviceConfig") == 0) {
+        if (field->type == GRPC_JSON_OBJECT) {
+          service_config_json = field;
+        }
+      }
+    }
+    if (service_config_json != NULL) {
+      service_config = grpc_json_dump_to_string(service_config_json, 0);
+      break;
+    }
+  }
+  grpc_json_destroy(choices_json);
+  return service_config;
+}
+
 static void dns_ares_on_resolved_locked(grpc_exec_ctx *exec_ctx, void *arg,
                                         grpc_error *error) {
   ares_dns_resolver *r = arg;
@@ -152,8 +233,40 @@
   r->resolving = false;
   r->pending_request = NULL;
   if (r->lb_addresses != NULL) {
-    grpc_arg new_arg = grpc_lb_addresses_create_channel_arg(r->lb_addresses);
-    result = grpc_channel_args_copy_and_add(r->channel_args, &new_arg, 1);
+    static const char *args_to_remove[2];
+    size_t num_args_to_remove = 0;
+    grpc_arg new_args[3];
+    size_t num_args_to_add = 0;
+    new_args[num_args_to_add++] =
+        grpc_lb_addresses_create_channel_arg(r->lb_addresses);
+    grpc_service_config *service_config = NULL;
+    char *service_config_string = NULL;
+    if (r->service_config_json != NULL) {
+      service_config_string = choose_service_config(r->service_config_json);
+      gpr_free(r->service_config_json);
+      if (service_config_string != NULL) {
+        gpr_log(GPR_INFO, "selected service config choice: %s",
+                service_config_string);
+        args_to_remove[num_args_to_remove++] = GRPC_ARG_SERVICE_CONFIG;
+        new_args[num_args_to_add++] = grpc_channel_arg_string_create(
+            GRPC_ARG_SERVICE_CONFIG, service_config_string);
+        service_config = grpc_service_config_create(service_config_string);
+        if (service_config != NULL) {
+          const char *lb_policy_name =
+              grpc_service_config_get_lb_policy_name(service_config);
+          if (lb_policy_name != NULL) {
+            args_to_remove[num_args_to_remove++] = GRPC_ARG_LB_POLICY_NAME;
+            new_args[num_args_to_add++] = grpc_channel_arg_string_create(
+                GRPC_ARG_LB_POLICY_NAME, (char *)lb_policy_name);
+          }
+        }
+      }
+    }
+    result = grpc_channel_args_copy_and_add_and_remove(
+        r->channel_args, args_to_remove, num_args_to_remove, new_args,
+        num_args_to_add);
+    if (service_config != NULL) grpc_service_config_destroy(service_config);
+    gpr_free(service_config_string);
     grpc_lb_addresses_destroy(exec_ctx, r->lb_addresses);
   } else {
     const char *msg = grpc_error_string(error);
@@ -207,10 +320,12 @@
   GPR_ASSERT(!r->resolving);
   r->resolving = true;
   r->lb_addresses = NULL;
+  r->service_config_json = NULL;
   r->pending_request = grpc_dns_lookup_ares(
       exec_ctx, r->dns_server, r->name_to_resolve, r->default_port,
       r->interested_parties, &r->dns_ares_on_resolved_locked, &r->lb_addresses,
-      true /* check_grpclb */);
+      true /* check_grpclb */,
+      r->request_service_config ? &r->service_config_json : NULL);
 }
 
 static void dns_ares_maybe_finish_next_locked(grpc_exec_ctx *exec_ctx,
@@ -256,6 +371,10 @@
   r->name_to_resolve = gpr_strdup(path);
   r->default_port = gpr_strdup(default_port);
   r->channel_args = grpc_channel_args_copy(args->args);
+  const grpc_arg *arg = grpc_channel_args_find(
+      r->channel_args, GRPC_ARG_SERVICE_CONFIG_DISABLE_RESOLUTION);
+  r->request_service_config = !grpc_channel_arg_get_integer(
+      arg, (grpc_integer_options){false, false, true});
   r->interested_parties = grpc_pollset_set_create();
   if (args->pollset_set != NULL) {
     grpc_pollset_set_add_pollset_set(exec_ctx, r->interested_parties,
diff --git a/src/core/ext/filters/client_channel/resolver/dns/c_ares/grpc_ares_wrapper.c b/src/core/ext/filters/client_channel/resolver/dns/c_ares/grpc_ares_wrapper.c
index 6ec3790..e65723a 100644
--- a/src/core/ext/filters/client_channel/resolver/dns/c_ares/grpc_ares_wrapper.c
+++ b/src/core/ext/filters/client_channel/resolver/dns/c_ares/grpc_ares_wrapper.c
@@ -54,6 +54,8 @@
   grpc_closure *on_done;
   /** the pointer to receive the resolved addresses */
   grpc_lb_addresses **lb_addrs_out;
+  /** the pointer to receive the service config in JSON */
+  char **service_config_json_out;
   /** the evernt driver used by this request */
   grpc_ares_ev_driver *ev_driver;
   /** number of ongoing queries */
@@ -266,10 +268,68 @@
   grpc_exec_ctx_finish(&exec_ctx);
 }
 
+static const char g_service_config_attribute_prefix[] = "grpc_config=";
+
+static void on_txt_done_cb(void *arg, int status, int timeouts,
+                           unsigned char *buf, int len) {
+  gpr_log(GPR_DEBUG, "on_txt_done_cb");
+  char *error_msg;
+  grpc_ares_request *r = (grpc_ares_request *)arg;
+  gpr_mu_lock(&r->mu);
+  if (status != ARES_SUCCESS) goto fail;
+  struct ares_txt_ext *reply = NULL;
+  status = ares_parse_txt_reply_ext(buf, len, &reply);
+  if (status != ARES_SUCCESS) goto fail;
+  // Find service config in TXT record.
+  const size_t prefix_len = sizeof(g_service_config_attribute_prefix) - 1;
+  struct ares_txt_ext *result;
+  for (result = reply; result != NULL; result = result->next) {
+    if (result->record_start &&
+        memcmp(result->txt, g_service_config_attribute_prefix, prefix_len) ==
+            0) {
+      break;
+    }
+  }
+  // Found a service config record.
+  if (result != NULL) {
+    size_t service_config_len = result->length - prefix_len;
+    *r->service_config_json_out = gpr_malloc(service_config_len + 1);
+    memcpy(*r->service_config_json_out, result->txt + prefix_len,
+           service_config_len);
+    for (result = result->next; result != NULL && !result->record_start;
+         result = result->next) {
+      *r->service_config_json_out = gpr_realloc(
+          *r->service_config_json_out, service_config_len + result->length + 1);
+      memcpy(*r->service_config_json_out + service_config_len, result->txt,
+             result->length);
+      service_config_len += result->length;
+    }
+    (*r->service_config_json_out)[service_config_len] = '\0';
+    gpr_log(GPR_INFO, "found service config: %s", *r->service_config_json_out);
+  }
+  // Clean up.
+  ares_free_data(reply);
+  goto done;
+fail:
+  gpr_asprintf(&error_msg, "C-ares TXT lookup status is not ARES_SUCCESS: %s",
+               ares_strerror(status));
+  grpc_error *error = GRPC_ERROR_CREATE_FROM_COPIED_STRING(error_msg);
+  gpr_free(error_msg);
+  if (r->error == GRPC_ERROR_NONE) {
+    r->error = error;
+  } else {
+    r->error = grpc_error_add_child(error, r->error);
+  }
+done:
+  gpr_mu_unlock(&r->mu);
+  grpc_ares_request_unref(NULL, r);
+}
+
 static grpc_ares_request *grpc_dns_lookup_ares_impl(
     grpc_exec_ctx *exec_ctx, const char *dns_server, const char *name,
     const char *default_port, grpc_pollset_set *interested_parties,
-    grpc_closure *on_done, grpc_lb_addresses **addrs, bool check_grpclb) {
+    grpc_closure *on_done, grpc_lb_addresses **addrs, bool check_grpclb,
+    char **service_config_json) {
   grpc_error *error = GRPC_ERROR_NONE;
   /* TODO(zyc): Enable tracing after #9603 is checked in */
   /* if (grpc_dns_trace) {
@@ -300,11 +360,12 @@
   error = grpc_ares_ev_driver_create(&ev_driver, interested_parties);
   if (error != GRPC_ERROR_NONE) goto error_cleanup;
 
-  grpc_ares_request *r = gpr_malloc(sizeof(grpc_ares_request));
+  grpc_ares_request *r = gpr_zalloc(sizeof(grpc_ares_request));
   gpr_mu_init(&r->mu);
   r->ev_driver = ev_driver;
   r->on_done = on_done;
   r->lb_addrs_out = addrs;
+  r->service_config_json_out = service_config_json;
   r->success = false;
   r->error = GRPC_ERROR_NONE;
   ares_channel *channel = grpc_ares_ev_driver_get_channel(r->ev_driver);
@@ -315,13 +376,17 @@
     grpc_resolved_address addr;
     if (grpc_parse_ipv4_hostport(dns_server, &addr, false /* log_errors */)) {
       r->dns_server_addr.family = AF_INET;
-      memcpy(&r->dns_server_addr.addr.addr4, addr.addr, addr.len);
+      struct sockaddr_in *in = (struct sockaddr_in *)addr.addr;
+      memcpy(&r->dns_server_addr.addr.addr4, &in->sin_addr,
+             sizeof(struct in_addr));
       r->dns_server_addr.tcp_port = grpc_sockaddr_get_port(&addr);
       r->dns_server_addr.udp_port = grpc_sockaddr_get_port(&addr);
     } else if (grpc_parse_ipv6_hostport(dns_server, &addr,
                                         false /* log_errors */)) {
       r->dns_server_addr.family = AF_INET6;
-      memcpy(&r->dns_server_addr.addr.addr6, addr.addr, addr.len);
+      struct sockaddr_in6 *in6 = (struct sockaddr_in6 *)addr.addr;
+      memcpy(&r->dns_server_addr.addr.addr6, &in6->sin6_addr,
+             sizeof(struct in6_addr));
       r->dns_server_addr.tcp_port = grpc_sockaddr_get_port(&addr);
       r->dns_server_addr.udp_port = grpc_sockaddr_get_port(&addr);
     } else {
@@ -342,8 +407,6 @@
       goto error_cleanup;
     }
   }
-  // An extra reference is put here to avoid destroying the request in
-  // on_done_cb before calling grpc_ares_ev_driver_start.
   gpr_ref_init(&r->pending_queries, 1);
   if (grpc_ipv6_loopback_available()) {
     grpc_ares_hostbyname_request *hr = create_hostbyname_request(
@@ -362,6 +425,10 @@
                r);
     gpr_free(service_name);
   }
+  if (service_config_json != NULL) {
+    grpc_ares_request_ref(r);
+    ares_search(*channel, hr->host, ns_c_in, ns_t_txt, on_txt_done_cb, r);
+  }
   /* TODO(zyc): Handle CNAME records here. */
   grpc_ares_ev_driver_start(exec_ctx, r->ev_driver);
   grpc_ares_request_unref(exec_ctx, r);
@@ -379,8 +446,8 @@
 grpc_ares_request *(*grpc_dns_lookup_ares)(
     grpc_exec_ctx *exec_ctx, const char *dns_server, const char *name,
     const char *default_port, grpc_pollset_set *interested_parties,
-    grpc_closure *on_done, grpc_lb_addresses **addrs,
-    bool check_grpclb) = grpc_dns_lookup_ares_impl;
+    grpc_closure *on_done, grpc_lb_addresses **addrs, bool check_grpclb,
+    char **service_config_json) = grpc_dns_lookup_ares_impl;
 
 void grpc_cancel_ares_request(grpc_exec_ctx *exec_ctx, grpc_ares_request *r) {
   if (grpc_dns_lookup_ares == grpc_dns_lookup_ares_impl) {
@@ -465,7 +532,8 @@
                     grpc_schedule_on_exec_ctx);
   grpc_dns_lookup_ares(exec_ctx, NULL /* dns_server */, name, default_port,
                        interested_parties, &r->on_dns_lookup_done, &r->lb_addrs,
-                       false /* check_grpclb */);
+                       false /* check_grpclb */,
+                       NULL /* service_config_json */);
 }
 
 void (*grpc_resolve_address_ares)(
diff --git a/src/core/ext/filters/client_channel/resolver/dns/c_ares/grpc_ares_wrapper.h b/src/core/ext/filters/client_channel/resolver/dns/c_ares/grpc_ares_wrapper.h
index 5d2d6c9..1083330 100644
--- a/src/core/ext/filters/client_channel/resolver/dns/c_ares/grpc_ares_wrapper.h
+++ b/src/core/ext/filters/client_channel/resolver/dns/c_ares/grpc_ares_wrapper.h
@@ -27,29 +27,30 @@
 
 typedef struct grpc_ares_request grpc_ares_request;
 
-/* Asynchronously resolve addr. Use \a default_port if a port isn't designated
-   in addr, otherwise use the port in addr. grpc_ares_init() must be called at
-   least once before this function. \a on_done may be called directly in this
-   function without being scheduled with \a exec_ctx, it must not try to acquire
-   locks that are being held by the caller. */
+/* Asynchronously resolve \a name. Use \a default_port if a port isn't
+   designated in \a name, otherwise use the port in \a name. grpc_ares_init()
+   must be called at least once before this function. \a on_done may be
+   called directly in this function without being scheduled with \a exec_ctx,
+   so it must not try to acquire locks that are being held by the caller. */
 extern void (*grpc_resolve_address_ares)(grpc_exec_ctx *exec_ctx,
-                                         const char *addr,
+                                         const char *name,
                                          const char *default_port,
                                          grpc_pollset_set *interested_parties,
                                          grpc_closure *on_done,
                                          grpc_resolved_addresses **addresses);
 
-/* Asynchronously resolve addr. It will try to resolve grpclb SRV records in
+/* Asynchronously resolve \a name. It will try to resolve grpclb SRV records in
   addition to the normal address records. For normal address records, it uses
-  \a default_port if a port isn't designated in \a addr, otherwise it uses the
-  port in \a addr. grpc_ares_init() must be called at least once before this
+  \a default_port if a port isn't designated in \a name, otherwise it uses the
+  port in \a name. grpc_ares_init() must be called at least once before this
   function. \a on_done may be called directly in this function without being
-  scheduled with \a exec_ctx, it must not try to acquire locks that are being
-  held by the caller. */
+  scheduled with \a exec_ctx, so it must not try to acquire locks that are
+  being held by the caller. */
 extern grpc_ares_request *(*grpc_dns_lookup_ares)(
-    grpc_exec_ctx *exec_ctx, const char *dns_server, const char *addr,
+    grpc_exec_ctx *exec_ctx, const char *dns_server, const char *name,
     const char *default_port, grpc_pollset_set *interested_parties,
-    grpc_closure *on_done, grpc_lb_addresses **addresses, bool check_grpclb);
+    grpc_closure *on_done, grpc_lb_addresses **addresses, bool check_grpclb,
+    char **service_config_json);
 
 /* Cancel the pending grpc_ares_request \a request */
 void grpc_cancel_ares_request(grpc_exec_ctx *exec_ctx,
diff --git a/src/core/ext/filters/client_channel/resolver/dns/c_ares/grpc_ares_wrapper_fallback.c b/src/core/ext/filters/client_channel/resolver/dns/c_ares/grpc_ares_wrapper_fallback.c
index b67636a..f2587c4 100644
--- a/src/core/ext/filters/client_channel/resolver/dns/c_ares/grpc_ares_wrapper_fallback.c
+++ b/src/core/ext/filters/client_channel/resolver/dns/c_ares/grpc_ares_wrapper_fallback.c
@@ -28,15 +28,16 @@
 static grpc_ares_request *grpc_dns_lookup_ares_impl(
     grpc_exec_ctx *exec_ctx, const char *dns_server, const char *name,
     const char *default_port, grpc_pollset_set *interested_parties,
-    grpc_closure *on_done, grpc_lb_addresses **addrs, bool check_grpclb) {
+    grpc_closure *on_done, grpc_lb_addresses **addrs, bool check_grpclb,
+    char **service_config_json) {
   return NULL;
 }
 
 grpc_ares_request *(*grpc_dns_lookup_ares)(
     grpc_exec_ctx *exec_ctx, const char *dns_server, const char *name,
     const char *default_port, grpc_pollset_set *interested_parties,
-    grpc_closure *on_done, grpc_lb_addresses **addrs,
-    bool check_grpclb) = grpc_dns_lookup_ares_impl;
+    grpc_closure *on_done, grpc_lb_addresses **addrs, bool check_grpclb,
+    char **service_config_json) = grpc_dns_lookup_ares_impl;
 
 void grpc_cancel_ares_request(grpc_exec_ctx *exec_ctx, grpc_ares_request *r) {}
 
diff --git a/src/core/ext/transport/chttp2/transport/chttp2_transport.c b/src/core/ext/transport/chttp2/transport/chttp2_transport.c
index aabe7b4..8976686 100644
--- a/src/core/ext/transport/chttp2/transport/chttp2_transport.c
+++ b/src/core/ext/transport/chttp2/transport/chttp2_transport.c
@@ -1788,9 +1788,8 @@
     bool pending_data = s->pending_byte_stream ||
                         s->unprocessed_incoming_frames_buffer.length > 0;
     if (s->stream_compression_recv_enabled && s->read_closed &&
-        s->frame_storage.length > 0 &&
-        s->unprocessed_incoming_frames_buffer.length == 0 && !pending_data &&
-        !s->seen_error && s->recv_trailing_metadata_finished != NULL) {
+        s->frame_storage.length > 0 && !pending_data && !s->seen_error &&
+        s->recv_trailing_metadata_finished != NULL) {
       /* Maybe some SYNC_FLUSH data is left in frame_storage. Consume them and
        * maybe decompress the next 5 bytes in the stream. */
       bool end_of_context;
@@ -1817,7 +1816,6 @@
       }
     }
     if (s->read_closed && s->frame_storage.length == 0 &&
-        s->unprocessed_incoming_frames_buffer.length == 0 &&
         (!pending_data || s->seen_error) &&
         s->recv_trailing_metadata_finished != NULL) {
       grpc_chttp2_incoming_metadata_buffer_publish(
diff --git a/src/core/ext/transport/cronet/transport/cronet_transport.c b/src/core/ext/transport/cronet/transport/cronet_transport.c
index 776e076..abb5589 100644
--- a/src/core/ext/transport/cronet/transport/cronet_transport.c
+++ b/src/core/ext/transport/cronet/transport/cronet_transport.c
@@ -637,7 +637,8 @@
  Utility function that takes the data from s->write_slice_buffer and assembles
  into a contiguous byte stream with 5 byte gRPC header prepended.
 */
-static void create_grpc_frame(grpc_slice_buffer *write_slice_buffer,
+static void create_grpc_frame(grpc_exec_ctx *exec_ctx,
+                              grpc_slice_buffer *write_slice_buffer,
                               char **pp_write_buffer,
                               size_t *p_write_buffer_size, uint32_t flags) {
   grpc_slice slice = grpc_slice_buffer_take_first(write_slice_buffer);
@@ -657,6 +658,7 @@
   *p++ = (uint8_t)(length);
   /* append actual data */
   memcpy(p, GRPC_SLICE_START_PTR(slice), length);
+  grpc_slice_unref_internal(exec_ctx, slice);
 }
 
 /*
@@ -1017,14 +1019,15 @@
       }
       if (write_slice_buffer.count > 0) {
         size_t write_buffer_size;
-        create_grpc_frame(&write_slice_buffer, &stream_state->ws.write_buffer,
-                          &write_buffer_size,
+        create_grpc_frame(exec_ctx, &write_slice_buffer,
+                          &stream_state->ws.write_buffer, &write_buffer_size,
                           stream_op->payload->send_message.send_message->flags);
         CRONET_LOG(GPR_DEBUG, "bidirectional_stream_write (%p, %p)", s->cbs,
                    stream_state->ws.write_buffer);
         stream_state->state_callback_received[OP_SEND_MESSAGE] = false;
         bidirectional_stream_write(s->cbs, stream_state->ws.write_buffer,
                                    (int)write_buffer_size, false);
+        grpc_slice_buffer_destroy_internal(exec_ctx, &write_slice_buffer);
         if (t->use_packet_coalescing) {
           if (!stream_op->send_trailing_metadata) {
             CRONET_LOG(GPR_DEBUG, "bidirectional_stream_flush (%p)", s->cbs);
@@ -1153,6 +1156,9 @@
         } else {
           stream_state->rs.remaining_bytes = 0;
           CRONET_LOG(GPR_DEBUG, "read operation complete. Empty response.");
+          /* Clean up read_slice_buffer in case there is unread data. */
+          grpc_slice_buffer_destroy_internal(
+              exec_ctx, &stream_state->rs.read_slice_buffer);
           grpc_slice_buffer_init(&stream_state->rs.read_slice_buffer);
           grpc_slice_buffer_stream_init(&stream_state->rs.sbs,
                                         &stream_state->rs.read_slice_buffer, 0);
@@ -1206,6 +1212,9 @@
       memcpy(dst_p, stream_state->rs.read_buffer,
              (size_t)stream_state->rs.length_field);
       null_and_maybe_free_read_buffer(s);
+      /* Clean up read_slice_buffer in case there is unread data. */
+      grpc_slice_buffer_destroy_internal(exec_ctx,
+                                         &stream_state->rs.read_slice_buffer);
       grpc_slice_buffer_init(&stream_state->rs.read_slice_buffer);
       grpc_slice_buffer_add(&stream_state->rs.read_slice_buffer,
                             read_data_slice);
@@ -1369,6 +1378,8 @@
                            grpc_closure *then_schedule_closure) {
   stream_obj *s = (stream_obj *)gs;
   null_and_maybe_free_read_buffer(s);
+  /* Clean up read_slice_buffer in case there is unread data. */
+  grpc_slice_buffer_destroy_internal(exec_ctx, &s->state.rs.read_slice_buffer);
   GRPC_ERROR_UNREF(s->state.cancel_error);
   GRPC_CLOSURE_SCHED(exec_ctx, then_schedule_closure, GRPC_ERROR_NONE);
 }
diff --git a/src/core/lib/iomgr/ev_epoll1_linux.c b/src/core/lib/iomgr/ev_epoll1_linux.c
index dc48d73..90e0ce3 100644
--- a/src/core/lib/iomgr/ev_epoll1_linux.c
+++ b/src/core/lib/iomgr/ev_epoll1_linux.c
@@ -237,28 +237,41 @@
 
 static int fd_wrapped_fd(grpc_fd *fd) { return fd->fd; }
 
-/* Might be called multiple times */
-static void fd_shutdown(grpc_exec_ctx *exec_ctx, grpc_fd *fd, grpc_error *why) {
+/* if 'releasing_fd' is true, it means that we are going to detach the internal
+ * fd from grpc_fd structure (i.e which means we should not be calling
+ * shutdown() syscall on that fd) */
+static void fd_shutdown_internal(grpc_exec_ctx *exec_ctx, grpc_fd *fd,
+                                 grpc_error *why, bool releasing_fd) {
   if (grpc_lfev_set_shutdown(exec_ctx, &fd->read_closure,
                              GRPC_ERROR_REF(why))) {
-    shutdown(fd->fd, SHUT_RDWR);
+    if (!releasing_fd) {
+      shutdown(fd->fd, SHUT_RDWR);
+    }
     grpc_lfev_set_shutdown(exec_ctx, &fd->write_closure, GRPC_ERROR_REF(why));
   }
   GRPC_ERROR_UNREF(why);
 }
 
+/* Might be called multiple times */
+static void fd_shutdown(grpc_exec_ctx *exec_ctx, grpc_fd *fd, grpc_error *why) {
+  fd_shutdown_internal(exec_ctx, fd, why, false);
+}
+
 static void fd_orphan(grpc_exec_ctx *exec_ctx, grpc_fd *fd,
                       grpc_closure *on_done, int *release_fd,
                       bool already_closed, const char *reason) {
   grpc_error *error = GRPC_ERROR_NONE;
+  bool is_release_fd = (release_fd != NULL);
 
   if (!grpc_lfev_is_shutdown(&fd->read_closure)) {
-    fd_shutdown(exec_ctx, fd, GRPC_ERROR_CREATE_FROM_COPIED_STRING(reason));
+    fd_shutdown_internal(exec_ctx, fd,
+                         GRPC_ERROR_CREATE_FROM_COPIED_STRING(reason),
+                         is_release_fd);
   }
 
   /* If release_fd is not NULL, we should be relinquishing control of the file
      descriptor fd->fd (but we still own the grpc_fd structure). */
-  if (release_fd != NULL) {
+  if (is_release_fd) {
     *release_fd = fd->fd;
   } else if (!already_closed) {
     close(fd->fd);
diff --git a/src/core/lib/iomgr/ev_poll_posix.c b/src/core/lib/iomgr/ev_poll_posix.c
index 365aa58..9472a8e 100644
--- a/src/core/lib/iomgr/ev_poll_posix.c
+++ b/src/core/lib/iomgr/ev_poll_posix.c
@@ -42,6 +42,7 @@
 #include "src/core/lib/iomgr/wakeup_fd_posix.h"
 #include "src/core/lib/profiling/timers.h"
 #include "src/core/lib/support/block_annotate.h"
+#include "src/core/lib/support/murmur_hash.h"
 
 #define GRPC_POLLSET_KICK_BROADCAST ((grpc_pollset_worker *)1)
 
@@ -239,22 +240,43 @@
  * condition variable polling definitions
  */
 
+#define POLLCV_THREAD_GRACE_MS 1000
 #define CV_POLL_PERIOD_MS 1000
 #define CV_DEFAULT_TABLE_SIZE 16
 
-typedef enum poll_status_t { INPROGRESS, COMPLETED, CANCELLED } poll_status_t;
-
-typedef struct poll_args {
+typedef struct poll_result {
   gpr_refcount refcount;
-  gpr_cv *cv;
+  cv_node *watchers;
+  int watchcount;
   struct pollfd *fds;
   nfds_t nfds;
-  int timeout;
   int retval;
   int err;
-  gpr_atm status;
+  int completed;
+} poll_result;
+
+typedef struct poll_args {
+  gpr_cv trigger;
+  int trigger_set;
+  struct pollfd *fds;
+  nfds_t nfds;
+  poll_result *result;
+  struct poll_args *next;
+  struct poll_args *prev;
 } poll_args;
 
+// This is a 2-tiered cache, we mantain a hash table
+// of active poll calls, so we can wait on the result
+// of that call.  We also maintain a freelist of inactive
+// poll threads.
+typedef struct poll_hash_table {
+  poll_args *free_pollers;
+  poll_args **active_pollers;
+  unsigned int size;
+  unsigned int count;
+} poll_hash_table;
+
+poll_hash_table poll_cache;
 cv_fd_table g_cvfds;
 
 /*******************************************************************************
@@ -1277,43 +1299,205 @@
  * Condition Variable polling extensions
  */
 
-static void decref_poll_args(poll_args *args) {
-  if (gpr_unref(&args->refcount)) {
-    gpr_free(args->fds);
-    gpr_cv_destroy(args->cv);
-    gpr_free(args->cv);
-    gpr_free(args);
+static void run_poll(void *args);
+static void cache_poller_locked(poll_args *args);
+
+static void cache_insert_locked(poll_args *args) {
+  uint32_t key = gpr_murmur_hash3(args->fds, args->nfds * sizeof(struct pollfd),
+                                  0xDEADBEEF);
+  key = key % poll_cache.size;
+  if (poll_cache.active_pollers[key]) {
+    poll_cache.active_pollers[key]->prev = args;
+  }
+  args->next = poll_cache.active_pollers[key];
+  args->prev = NULL;
+  poll_cache.active_pollers[key] = args;
+  poll_cache.count++;
+}
+
+static void init_result(poll_args *pargs) {
+  pargs->result = gpr_malloc(sizeof(poll_result));
+  gpr_ref_init(&pargs->result->refcount, 1);
+  pargs->result->watchers = NULL;
+  pargs->result->watchcount = 0;
+  pargs->result->fds = gpr_malloc(sizeof(struct pollfd) * pargs->nfds);
+  memcpy(pargs->result->fds, pargs->fds, sizeof(struct pollfd) * pargs->nfds);
+  pargs->result->nfds = pargs->nfds;
+  pargs->result->retval = 0;
+  pargs->result->err = 0;
+  pargs->result->completed = 0;
+}
+
+// Creates a poll_args object for a given arguments to poll().
+// This object may return a poll_args in the cache.
+static poll_args *get_poller_locked(struct pollfd *fds, nfds_t count) {
+  uint32_t key =
+      gpr_murmur_hash3(fds, count * sizeof(struct pollfd), 0xDEADBEEF);
+  key = key % poll_cache.size;
+  poll_args *curr = poll_cache.active_pollers[key];
+  while (curr) {
+    if (curr->nfds == count &&
+        memcmp(curr->fds, fds, count * sizeof(struct pollfd)) == 0) {
+      gpr_free(fds);
+      return curr;
+    }
+    curr = curr->next;
+  }
+
+  if (poll_cache.free_pollers) {
+    poll_args *pargs = poll_cache.free_pollers;
+    poll_cache.free_pollers = pargs->next;
+    if (poll_cache.free_pollers) {
+      poll_cache.free_pollers->prev = NULL;
+    }
+    pargs->fds = fds;
+    pargs->nfds = count;
+    pargs->next = NULL;
+    pargs->prev = NULL;
+    init_result(pargs);
+    cache_poller_locked(pargs);
+    return pargs;
+  }
+
+  poll_args *pargs = gpr_malloc(sizeof(struct poll_args));
+  gpr_cv_init(&pargs->trigger);
+  pargs->fds = fds;
+  pargs->nfds = count;
+  pargs->next = NULL;
+  pargs->prev = NULL;
+  pargs->trigger_set = 0;
+  init_result(pargs);
+  cache_poller_locked(pargs);
+  gpr_thd_id t_id;
+  gpr_thd_options opt = gpr_thd_options_default();
+  gpr_ref(&g_cvfds.pollcount);
+  gpr_thd_options_set_detached(&opt);
+  GPR_ASSERT(gpr_thd_new(&t_id, &run_poll, pargs, &opt));
+  return pargs;
+}
+
+static void cache_delete_locked(poll_args *args) {
+  if (!args->prev) {
+    uint32_t key = gpr_murmur_hash3(
+        args->fds, args->nfds * sizeof(struct pollfd), 0xDEADBEEF);
+    key = key % poll_cache.size;
+    GPR_ASSERT(poll_cache.active_pollers[key] == args);
+    poll_cache.active_pollers[key] = args->next;
+  } else {
+    args->prev->next = args->next;
+  }
+
+  if (args->next) {
+    args->next->prev = args->prev;
+  }
+
+  poll_cache.count--;
+  if (poll_cache.free_pollers) {
+    poll_cache.free_pollers->prev = args;
+  }
+  args->prev = NULL;
+  args->next = poll_cache.free_pollers;
+  gpr_free(args->fds);
+  poll_cache.free_pollers = args;
+}
+
+static void cache_poller_locked(poll_args *args) {
+  if (poll_cache.count + 1 > poll_cache.size / 2) {
+    poll_args **old_active_pollers = poll_cache.active_pollers;
+    poll_cache.size = poll_cache.size * 2;
+    poll_cache.count = 0;
+    poll_cache.active_pollers = gpr_malloc(sizeof(void *) * poll_cache.size);
+    for (unsigned int i = 0; i < poll_cache.size; i++) {
+      poll_cache.active_pollers[i] = NULL;
+    }
+    for (unsigned int i = 0; i < poll_cache.size / 2; i++) {
+      poll_args *curr = old_active_pollers[i];
+      poll_args *next = NULL;
+      while (curr) {
+        next = curr->next;
+        cache_insert_locked(curr);
+        curr = next;
+      }
+    }
+    gpr_free(old_active_pollers);
+  }
+
+  cache_insert_locked(args);
+}
+
+static void cache_destroy_locked(poll_args *args) {
+  if (args->next) {
+    args->next->prev = args->prev;
+  }
+
+  if (args->prev) {
+    args->prev->next = args->next;
+  } else {
+    poll_cache.free_pollers = args->next;
+  }
+
+  gpr_free(args);
+}
+
+static void decref_poll_result(poll_result *res) {
+  if (gpr_unref(&res->refcount)) {
+    GPR_ASSERT(!res->watchers);
+    gpr_free(res->fds);
+    gpr_free(res);
   }
 }
 
+void remove_cvn(cv_node **head, cv_node *target) {
+  if (target->next) {
+    target->next->prev = target->prev;
+  }
+
+  if (target->prev) {
+    target->prev->next = target->next;
+  } else {
+    *head = target->next;
+  }
+}
+
+gpr_timespec thread_grace;
+
 // Poll in a background thread
-static void run_poll(void *arg) {
-  int timeout, retval;
-  poll_args *pargs = (poll_args *)arg;
-  while (gpr_atm_no_barrier_load(&pargs->status) == INPROGRESS) {
-    if (pargs->timeout < 0) {
-      timeout = CV_POLL_PERIOD_MS;
-    } else {
-      timeout = GPR_MIN(CV_POLL_PERIOD_MS, pargs->timeout);
-      pargs->timeout -= timeout;
+static void run_poll(void *args) {
+  poll_args *pargs = (poll_args *)args;
+  while (1) {
+    poll_result *result = pargs->result;
+    int retval = g_cvfds.poll(result->fds, result->nfds, CV_POLL_PERIOD_MS);
+    gpr_mu_lock(&g_cvfds.mu);
+    if (retval != 0) {
+      result->completed = 1;
+      result->retval = retval;
+      result->err = errno;
+      cv_node *watcher = result->watchers;
+      while (watcher) {
+        gpr_cv_signal(watcher->cv);
+        watcher = watcher->next;
+      }
     }
-    retval = g_cvfds.poll(pargs->fds, pargs->nfds, timeout);
-    if (retval != 0 || pargs->timeout == 0) {
-      pargs->retval = retval;
-      pargs->err = errno;
-      break;
+    if (result->watchcount == 0 || result->completed) {
+      cache_delete_locked(pargs);
+      decref_poll_result(result);
+      // Leave this polling thread alive for a grace period to do another poll()
+      // op
+      gpr_timespec deadline = gpr_now(GPR_CLOCK_REALTIME);
+      deadline = gpr_time_add(deadline, thread_grace);
+      pargs->trigger_set = 0;
+      gpr_cv_wait(&pargs->trigger, &g_cvfds.mu, deadline);
+      if (!pargs->trigger_set) {
+        cache_destroy_locked(pargs);
+        break;
+      }
     }
+    gpr_mu_unlock(&g_cvfds.mu);
   }
-  gpr_mu_lock(&g_cvfds.mu);
-  if (gpr_atm_no_barrier_load(&pargs->status) == INPROGRESS) {
-    // Signal main thread that the poll completed
-    gpr_atm_no_barrier_store(&pargs->status, COMPLETED);
-    gpr_cv_signal(pargs->cv);
-  }
-  decref_poll_args(pargs);
-  g_cvfds.pollcount--;
-  if (g_cvfds.shutdown && g_cvfds.pollcount == 0) {
-    gpr_cv_signal(&g_cvfds.shutdown_complete);
+
+  // We still have the lock here
+  if (gpr_unref(&g_cvfds.pollcount)) {
+    gpr_cv_signal(&g_cvfds.shutdown_cv);
   }
   gpr_mu_unlock(&g_cvfds.mu);
 }
@@ -1322,24 +1506,29 @@
 static int cvfd_poll(struct pollfd *fds, nfds_t nfds, int timeout) {
   unsigned int i;
   int res, idx;
-  gpr_cv *pollcv;
-  cv_node *cvn, *prev;
+  cv_node *pollcv;
   int skip_poll = 0;
   nfds_t nsockfds = 0;
-  gpr_thd_id t_id;
-  gpr_thd_options opt;
-  poll_args *pargs = NULL;
+  poll_result *result = NULL;
   gpr_mu_lock(&g_cvfds.mu);
-  pollcv = gpr_malloc(sizeof(gpr_cv));
-  gpr_cv_init(pollcv);
+  pollcv = gpr_malloc(sizeof(cv_node));
+  pollcv->next = NULL;
+  gpr_cv pollcv_cv;
+  gpr_cv_init(&pollcv_cv);
+  pollcv->cv = &pollcv_cv;
+  cv_node *fd_cvs = gpr_malloc(nfds * sizeof(cv_node));
+
   for (i = 0; i < nfds; i++) {
     fds[i].revents = 0;
     if (fds[i].fd < 0 && (fds[i].events & POLLIN)) {
       idx = FD_TO_IDX(fds[i].fd);
-      cvn = gpr_malloc(sizeof(cv_node));
-      cvn->cv = pollcv;
-      cvn->next = g_cvfds.cvfds[idx].cvs;
-      g_cvfds.cvfds[idx].cvs = cvn;
+      fd_cvs[i].cv = &pollcv_cv;
+      fd_cvs[i].prev = NULL;
+      fd_cvs[i].next = g_cvfds.cvfds[idx].cvs;
+      if (g_cvfds.cvfds[idx].cvs) {
+        g_cvfds.cvfds[idx].cvs->prev = &(fd_cvs[i]);
+      }
+      g_cvfds.cvfds[idx].cvs = &(fd_cvs[i]);
       // Don't bother polling if a wakeup fd is ready
       if (g_cvfds.cvfds[idx].is_set) {
         skip_poll = 1;
@@ -1349,81 +1538,68 @@
     }
   }
 
+  gpr_timespec deadline = gpr_now(GPR_CLOCK_REALTIME);
+  if (timeout < 0) {
+    deadline = gpr_inf_future(GPR_CLOCK_REALTIME);
+  } else {
+    deadline =
+        gpr_time_add(deadline, gpr_time_from_millis(timeout, GPR_TIMESPAN));
+  }
+
   res = 0;
   if (!skip_poll && nsockfds > 0) {
-    pargs = gpr_malloc(sizeof(struct poll_args));
-    // Both the main thread and calling thread get a reference
-    gpr_ref_init(&pargs->refcount, 2);
-    pargs->cv = pollcv;
-    pargs->fds = gpr_malloc(sizeof(struct pollfd) * nsockfds);
-    pargs->nfds = nsockfds;
-    pargs->timeout = timeout;
-    pargs->retval = 0;
-    pargs->err = 0;
-    gpr_atm_no_barrier_store(&pargs->status, INPROGRESS);
+    struct pollfd *pollfds = gpr_malloc(sizeof(struct pollfd) * nsockfds);
     idx = 0;
     for (i = 0; i < nfds; i++) {
       if (fds[i].fd >= 0) {
-        pargs->fds[idx].fd = fds[i].fd;
-        pargs->fds[idx].events = fds[i].events;
-        pargs->fds[idx].revents = 0;
+        pollfds[idx].fd = fds[i].fd;
+        pollfds[idx].events = fds[i].events;
+        pollfds[idx].revents = 0;
         idx++;
       }
     }
-    g_cvfds.pollcount++;
-    opt = gpr_thd_options_default();
-    gpr_thd_options_set_detached(&opt);
-    GPR_ASSERT(gpr_thd_new(&t_id, &run_poll, pargs, &opt));
-    // We want the poll() thread to trigger the deadline, so wait forever here
-    gpr_cv_wait(pollcv, &g_cvfds.mu, gpr_inf_future(GPR_CLOCK_MONOTONIC));
-    if (gpr_atm_no_barrier_load(&pargs->status) == COMPLETED) {
-      res = pargs->retval;
-      errno = pargs->err;
-    } else {
-      errno = 0;
-      gpr_atm_no_barrier_store(&pargs->status, CANCELLED);
+    poll_args *pargs = get_poller_locked(pollfds, nsockfds);
+    result = pargs->result;
+    pollcv->next = result->watchers;
+    pollcv->prev = NULL;
+    if (result->watchers) {
+      result->watchers->prev = pollcv;
     }
+    result->watchers = pollcv;
+    result->watchcount++;
+    gpr_ref(&result->refcount);
+
+    pargs->trigger_set = 1;
+    gpr_cv_signal(&pargs->trigger);
+    gpr_cv_wait(&pollcv_cv, &g_cvfds.mu, deadline);
+    res = result->retval;
+    errno = result->err;
+    result->watchcount--;
+    remove_cvn(&result->watchers, pollcv);
   } else if (!skip_poll) {
-    gpr_timespec deadline = gpr_now(GPR_CLOCK_REALTIME);
-    deadline =
-        gpr_time_add(deadline, gpr_time_from_millis(timeout, GPR_TIMESPAN));
-    gpr_cv_wait(pollcv, &g_cvfds.mu, deadline);
+    gpr_cv_wait(&pollcv_cv, &g_cvfds.mu, deadline);
   }
 
   idx = 0;
   for (i = 0; i < nfds; i++) {
     if (fds[i].fd < 0 && (fds[i].events & POLLIN)) {
-      cvn = g_cvfds.cvfds[FD_TO_IDX(fds[i].fd)].cvs;
-      prev = NULL;
-      while (cvn->cv != pollcv) {
-        prev = cvn;
-        cvn = cvn->next;
-        GPR_ASSERT(cvn);
-      }
-      if (!prev) {
-        g_cvfds.cvfds[FD_TO_IDX(fds[i].fd)].cvs = cvn->next;
-      } else {
-        prev->next = cvn->next;
-      }
-      gpr_free(cvn);
-
+      remove_cvn(&g_cvfds.cvfds[FD_TO_IDX(fds[i].fd)].cvs, &(fd_cvs[i]));
       if (g_cvfds.cvfds[FD_TO_IDX(fds[i].fd)].is_set) {
         fds[i].revents = POLLIN;
         if (res >= 0) res++;
       }
-    } else if (!skip_poll && fds[i].fd >= 0 &&
-               gpr_atm_no_barrier_load(&pargs->status) == COMPLETED) {
-      fds[i].revents = pargs->fds[idx].revents;
+    } else if (!skip_poll && fds[i].fd >= 0 && result->completed) {
+      fds[i].revents = result->fds[idx].revents;
       idx++;
     }
   }
 
-  if (pargs) {
-    decref_poll_args(pargs);
-  } else {
-    gpr_cv_destroy(pollcv);
-    gpr_free(pollcv);
+  gpr_free(fd_cvs);
+  gpr_free(pollcv);
+  if (result) {
+    decref_poll_result(result);
   }
+
   gpr_mu_unlock(&g_cvfds.mu);
 
   return res;
@@ -1432,12 +1608,12 @@
 static void global_cv_fd_table_init() {
   gpr_mu_init(&g_cvfds.mu);
   gpr_mu_lock(&g_cvfds.mu);
-  gpr_cv_init(&g_cvfds.shutdown_complete);
-  g_cvfds.shutdown = 0;
-  g_cvfds.pollcount = 0;
+  gpr_cv_init(&g_cvfds.shutdown_cv);
+  gpr_ref_init(&g_cvfds.pollcount, 1);
   g_cvfds.size = CV_DEFAULT_TABLE_SIZE;
   g_cvfds.cvfds = gpr_malloc(sizeof(fd_node) * CV_DEFAULT_TABLE_SIZE);
   g_cvfds.free_fds = NULL;
+  thread_grace = gpr_time_from_millis(POLLCV_THREAD_GRACE_MS, GPR_TIMESPAN);
   for (int i = 0; i < CV_DEFAULT_TABLE_SIZE; i++) {
     g_cvfds.cvfds[i].is_set = 0;
     g_cvfds.cvfds[i].cvs = NULL;
@@ -1447,23 +1623,35 @@
   // Override the poll function with one that supports cvfds
   g_cvfds.poll = grpc_poll_function;
   grpc_poll_function = &cvfd_poll;
+
+  // Initialize the cache
+  poll_cache.size = 32;
+  poll_cache.count = 0;
+  poll_cache.free_pollers = NULL;
+  poll_cache.active_pollers = gpr_malloc(sizeof(void *) * 32);
+  for (unsigned int i = 0; i < poll_cache.size; i++) {
+    poll_cache.active_pollers[i] = NULL;
+  }
+
   gpr_mu_unlock(&g_cvfds.mu);
 }
 
 static void global_cv_fd_table_shutdown() {
   gpr_mu_lock(&g_cvfds.mu);
-  g_cvfds.shutdown = 1;
   // Attempt to wait for all abandoned poll() threads to terminate
   // Not doing so will result in reported memory leaks
-  if (g_cvfds.pollcount > 0) {
-    int res = gpr_cv_wait(&g_cvfds.shutdown_complete, &g_cvfds.mu,
+  if (!gpr_unref(&g_cvfds.pollcount)) {
+    int res = gpr_cv_wait(&g_cvfds.shutdown_cv, &g_cvfds.mu,
                           gpr_time_add(gpr_now(GPR_CLOCK_REALTIME),
                                        gpr_time_from_seconds(3, GPR_TIMESPAN)));
     GPR_ASSERT(res == 0);
   }
-  gpr_cv_destroy(&g_cvfds.shutdown_complete);
+  gpr_cv_destroy(&g_cvfds.shutdown_cv);
   grpc_poll_function = g_cvfds.poll;
   gpr_free(g_cvfds.cvfds);
+
+  gpr_free(poll_cache.active_pollers);
+
   gpr_mu_unlock(&g_cvfds.mu);
   gpr_mu_destroy(&g_cvfds.mu);
 }
diff --git a/src/core/lib/iomgr/exec_ctx.c b/src/core/lib/iomgr/exec_ctx.c
index 833170c..41c69ad 100644
--- a/src/core/lib/iomgr/exec_ctx.c
+++ b/src/core/lib/iomgr/exec_ctx.c
@@ -51,33 +51,6 @@
          !grpc_closure_list_empty(exec_ctx->closure_list);
 }
 
-bool grpc_exec_ctx_flush(grpc_exec_ctx *exec_ctx) {
-  bool did_something = 0;
-  GPR_TIMER_BEGIN("grpc_exec_ctx_flush", 0);
-  for (;;) {
-    if (!grpc_closure_list_empty(exec_ctx->closure_list)) {
-      grpc_closure *c = exec_ctx->closure_list.head;
-      exec_ctx->closure_list.head = exec_ctx->closure_list.tail = NULL;
-      while (c != NULL) {
-        grpc_closure *next = c->next_data.next;
-        grpc_error *error = c->error_data.error;
-        did_something = true;
-#ifndef NDEBUG
-        c->scheduled = false;
-#endif
-        c->cb(exec_ctx, c->cb_arg, error);
-        GRPC_ERROR_UNREF(error);
-        c = next;
-      }
-    } else if (!grpc_combiner_continue_exec_ctx(exec_ctx)) {
-      break;
-    }
-  }
-  GPR_ASSERT(exec_ctx->active_combiner == NULL);
-  GPR_TIMER_END("grpc_exec_ctx_flush", 0);
-  return did_something;
-}
-
 void grpc_exec_ctx_finish(grpc_exec_ctx *exec_ctx) {
   exec_ctx->flags |= GRPC_EXEC_CTX_FLAG_IS_FINISHED;
   grpc_exec_ctx_flush(exec_ctx);
@@ -103,6 +76,29 @@
   GRPC_ERROR_UNREF(error);
 }
 
+bool grpc_exec_ctx_flush(grpc_exec_ctx *exec_ctx) {
+  bool did_something = 0;
+  GPR_TIMER_BEGIN("grpc_exec_ctx_flush", 0);
+  for (;;) {
+    if (!grpc_closure_list_empty(exec_ctx->closure_list)) {
+      grpc_closure *c = exec_ctx->closure_list.head;
+      exec_ctx->closure_list.head = exec_ctx->closure_list.tail = NULL;
+      while (c != NULL) {
+        grpc_closure *next = c->next_data.next;
+        grpc_error *error = c->error_data.error;
+        did_something = true;
+        exec_ctx_run(exec_ctx, c, error);
+        c = next;
+      }
+    } else if (!grpc_combiner_continue_exec_ctx(exec_ctx)) {
+      break;
+    }
+  }
+  GPR_ASSERT(exec_ctx->active_combiner == NULL);
+  GPR_TIMER_END("grpc_exec_ctx_flush", 0);
+  return did_something;
+}
+
 static void exec_ctx_sched(grpc_exec_ctx *exec_ctx, grpc_closure *closure,
                            grpc_error *error) {
   grpc_closure_list_append(&exec_ctx->closure_list, closure, error);
diff --git a/src/core/lib/iomgr/gethostname.h b/src/core/lib/iomgr/gethostname.h
new file mode 100644
index 0000000..9c6b9d8
--- /dev/null
+++ b/src/core/lib/iomgr/gethostname.h
@@ -0,0 +1,26 @@
+/*
+ *
+ * Copyright 2017 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+#ifndef GRPC_CORE_LIB_IOMGR_GETHOSTNAME_H
+#define GRPC_CORE_LIB_IOMGR_GETHOSTNAME_H
+
+// Returns the hostname of the local machine.
+// Caller takes ownership of result.
+char *grpc_gethostname();
+
+#endif /* GRPC_CORE_LIB_IOMGR_GETHOSTNAME_H */
diff --git a/src/core/lib/iomgr/gethostname_fallback.c b/src/core/lib/iomgr/gethostname_fallback.c
new file mode 100644
index 0000000..6229461
--- /dev/null
+++ b/src/core/lib/iomgr/gethostname_fallback.c
@@ -0,0 +1,27 @@
+/*
+ *
+ * Copyright 2017 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+#include "src/core/lib/iomgr/port.h"
+
+#ifdef GRPC_GETHOSTNAME_FALLBACK
+
+#include <stddef.h>
+
+char *grpc_gethostname() { return NULL; }
+
+#endif  // GRPC_GETHOSTNAME_FALLBACK
diff --git a/src/core/lib/iomgr/gethostname_host_name_max.c b/src/core/lib/iomgr/gethostname_host_name_max.c
new file mode 100644
index 0000000..4d05114
--- /dev/null
+++ b/src/core/lib/iomgr/gethostname_host_name_max.c
@@ -0,0 +1,37 @@
+/*
+ *
+ * Copyright 2017 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+#include "src/core/lib/iomgr/port.h"
+
+#ifdef GRPC_POSIX_HOST_NAME_MAX
+
+#include <limits.h>
+#include <unistd.h>
+
+#include <grpc/support/alloc.h>
+
+char *grpc_gethostname() {
+  char *hostname = (char *)gpr_malloc(HOST_NAME_MAX);
+  if (gethostname(hostname, HOST_NAME_MAX) != 0) {
+    gpr_free(hostname);
+    return NULL;
+  }
+  return hostname;
+}
+
+#endif  // GRPC_POSIX_HOST_NAME_MAX
diff --git a/src/core/lib/iomgr/gethostname_sysconf.c b/src/core/lib/iomgr/gethostname_sysconf.c
new file mode 100644
index 0000000..51bac5d
--- /dev/null
+++ b/src/core/lib/iomgr/gethostname_sysconf.c
@@ -0,0 +1,37 @@
+/*
+ *
+ * Copyright 2017 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+#include "src/core/lib/iomgr/port.h"
+
+#ifdef GRPC_POSIX_SYSCONF
+
+#include <unistd.h>
+
+#include <grpc/support/alloc.h>
+
+char *grpc_gethostname() {
+  size_t host_name_max = (size_t)sysconf(_SC_HOST_NAME_MAX);
+  char *hostname = (char *)gpr_malloc(host_name_max);
+  if (gethostname(hostname, host_name_max) != 0) {
+    gpr_free(hostname);
+    return NULL;
+  }
+  return hostname;
+}
+
+#endif  // GRPC_POSIX_SYSCONF
diff --git a/src/core/lib/iomgr/port.h b/src/core/lib/iomgr/port.h
index c12058f..42033d0 100644
--- a/src/core/lib/iomgr/port.h
+++ b/src/core/lib/iomgr/port.h
@@ -59,6 +59,7 @@
 #define GRPC_HAVE_MSG_NOSIGNAL 1
 #define GRPC_HAVE_UNIX_SOCKET 1
 #define GRPC_LINUX_MULTIPOLL_WITH_EPOLL 1
+#define GRPC_POSIX_HOST_NAME_MAX 1
 #define GRPC_POSIX_SOCKET 1
 #define GRPC_POSIX_SOCKETADDR 1
 #define GRPC_POSIX_WAKEUP_FD 1
@@ -93,6 +94,7 @@
 #define GRPC_POSIX_SOCKET 1
 #define GRPC_POSIX_SOCKETADDR 1
 #define GRPC_POSIX_SOCKETUTILS 1
+#define GRPC_POSIX_SYSCONF 1
 #define GRPC_POSIX_WAKEUP_FD 1
 #define GRPC_TIMER_USE_GENERIC 1
 #elif defined(GPR_FREEBSD)
@@ -125,4 +127,11 @@
 #error Must define exactly one of GRPC_POSIX_SOCKET, GRPC_WINSOCK_SOCKET, GPR_CUSTOM_SOCKET
 #endif
 
+#if defined(GRPC_POSIX_HOST_NAME_MAX) && defined(GRPC_POSIX_SYSCONF)
+#error "Cannot define both GRPC_POSIX_HOST_NAME_MAX and GRPC_POSIX_SYSCONF"
+#endif
+#if !defined(GRPC_POSIX_HOST_NAME_MAX) && !defined(GRPC_POSIX_SYSCONF)
+#define GRPC_GETHOSTNAME_FALLBACK 1
+#endif
+
 #endif /* GRPC_CORE_LIB_IOMGR_PORT_H */
diff --git a/src/core/lib/iomgr/tcp_server_utils_posix_common.c b/src/core/lib/iomgr/tcp_server_utils_posix_common.c
index dbb4318..ad535bc 100644
--- a/src/core/lib/iomgr/tcp_server_utils_posix_common.c
+++ b/src/core/lib/iomgr/tcp_server_utils_posix_common.c
@@ -39,7 +39,7 @@
 
 #define MIN_SAFE_ACCEPT_QUEUE_SIZE 100
 
-static gpr_once s_init_max_accept_queue_size;
+static gpr_once s_init_max_accept_queue_size = GPR_ONCE_INIT;
 static int s_max_accept_queue_size;
 
 /* get max listen queue size on linux */
diff --git a/src/core/lib/iomgr/wakeup_fd_cv.h b/src/core/lib/iomgr/wakeup_fd_cv.h
index c5dcdc9..46e84f5 100644
--- a/src/core/lib/iomgr/wakeup_fd_cv.h
+++ b/src/core/lib/iomgr/wakeup_fd_cv.h
@@ -43,6 +43,7 @@
 typedef struct cv_node {
   gpr_cv* cv;
   struct cv_node* next;
+  struct cv_node* prev;
 } cv_node;
 
 typedef struct fd_node {
@@ -53,9 +54,8 @@
 
 typedef struct cv_fd_table {
   gpr_mu mu;
-  int pollcount;
-  int shutdown;
-  gpr_cv shutdown_complete;
+  gpr_refcount pollcount;
+  gpr_cv shutdown_cv;
   fd_node* cvfds;
   fd_node* free_fds;
   unsigned int size;
diff --git a/src/core/lib/security/transport/security_handshaker.c b/src/core/lib/security/transport/security_handshaker.c
index b9da6e1..fc9c9f9 100644
--- a/src/core/lib/security/transport/security_handshaker.c
+++ b/src/core/lib/security/transport/security_handshaker.c
@@ -261,7 +261,7 @@
     grpc_exec_ctx *exec_ctx, security_handshaker *h,
     const unsigned char *bytes_received, size_t bytes_received_size) {
   // Invoke TSI handshaker.
-  unsigned char *bytes_to_send = NULL;
+  const unsigned char *bytes_to_send = NULL;
   size_t bytes_to_send_size = 0;
   tsi_handshaker_result *handshaker_result = NULL;
   tsi_result result = tsi_handshaker_next(
diff --git a/src/core/lib/surface/alarm.c b/src/core/lib/surface/alarm.c
index 5593496..7d60b1d 100644
--- a/src/core/lib/surface/alarm.c
+++ b/src/core/lib/surface/alarm.c
@@ -15,6 +15,7 @@
  * limitations under the License.
  *
  */
+#include "src/core/lib/surface/alarm_internal.h"
 
 #include <grpc/grpc.h>
 #include <grpc/support/alloc.h>
@@ -22,7 +23,13 @@
 #include "src/core/lib/iomgr/timer.h"
 #include "src/core/lib/surface/completion_queue.h"
 
+#ifndef NDEBUG
+grpc_tracer_flag grpc_trace_alarm_refcount =
+    GRPC_TRACER_INITIALIZER(false, "alarm_refcount");
+#endif
+
 struct grpc_alarm {
+  gpr_refcount refs;
   grpc_timer alarm;
   grpc_closure on_alarm;
   grpc_cq_completion completion;
@@ -32,13 +39,58 @@
   void *tag;
 };
 
-static void do_nothing_end_completion(grpc_exec_ctx *exec_ctx, void *arg,
-                                      grpc_cq_completion *c) {}
+static void alarm_ref(grpc_alarm *alarm) { gpr_ref(&alarm->refs); }
+
+static void alarm_unref(grpc_alarm *alarm) {
+  if (gpr_unref(&alarm->refs)) {
+    grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
+    GRPC_CQ_INTERNAL_UNREF(&exec_ctx, alarm->cq, "alarm");
+    grpc_exec_ctx_finish(&exec_ctx);
+    gpr_free(alarm);
+  }
+}
+
+#ifndef NDEBUG
+static void alarm_ref_dbg(grpc_alarm *alarm, const char *reason,
+                          const char *file, int line) {
+  if (GRPC_TRACER_ON(grpc_trace_alarm_refcount)) {
+    gpr_atm val = gpr_atm_no_barrier_load(&alarm->refs.count);
+    gpr_log(file, line, GPR_LOG_SEVERITY_DEBUG,
+            "Alarm:%p  ref %" PRIdPTR " -> %" PRIdPTR " %s", alarm, val,
+            val + 1, reason);
+  }
+
+  alarm_ref(alarm);
+}
+
+static void alarm_unref_dbg(grpc_alarm *alarm, const char *reason,
+                            const char *file, int line) {
+  if (GRPC_TRACER_ON(grpc_trace_alarm_refcount)) {
+    gpr_atm val = gpr_atm_no_barrier_load(&alarm->refs.count);
+    gpr_log(file, line, GPR_LOG_SEVERITY_DEBUG,
+            "Alarm:%p  Unref %" PRIdPTR " -> %" PRIdPTR " %s", alarm, val,
+            val - 1, reason);
+  }
+
+  alarm_unref(alarm);
+}
+#endif
+
+static void alarm_end_completion(grpc_exec_ctx *exec_ctx, void *arg,
+                                 grpc_cq_completion *c) {
+  grpc_alarm *alarm = arg;
+  GRPC_ALARM_UNREF(alarm, "dequeue-end-op");
+}
 
 static void alarm_cb(grpc_exec_ctx *exec_ctx, void *arg, grpc_error *error) {
   grpc_alarm *alarm = arg;
-  grpc_cq_end_op(exec_ctx, alarm->cq, alarm->tag, error,
-                 do_nothing_end_completion, NULL, &alarm->completion);
+
+  /* We are queuing an op on completion queue. This means, the alarm's structure
+     cannot be destroyed until the op is dequeued. Adding an extra ref
+     here and unref'ing when the op is dequeued will achieve this */
+  GRPC_ALARM_REF(alarm, "queue-end-op");
+  grpc_cq_end_op(exec_ctx, alarm->cq, alarm->tag, error, alarm_end_completion,
+                 (void *)alarm, &alarm->completion);
 }
 
 grpc_alarm *grpc_alarm_create(grpc_completion_queue *cq, gpr_timespec deadline,
@@ -46,6 +98,14 @@
   grpc_alarm *alarm = gpr_malloc(sizeof(grpc_alarm));
   grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
 
+  gpr_ref_init(&alarm->refs, 1);
+
+#ifndef NDEBUG
+  if (GRPC_TRACER_ON(grpc_trace_alarm_refcount)) {
+    gpr_log(GPR_DEBUG, "Alarm:%p created (ref: 1)", alarm);
+  }
+#endif
+
   GRPC_CQ_INTERNAL_REF(cq, "alarm");
   alarm->cq = cq;
   alarm->tag = tag;
@@ -67,9 +127,6 @@
 }
 
 void grpc_alarm_destroy(grpc_alarm *alarm) {
-  grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
   grpc_alarm_cancel(alarm);
-  GRPC_CQ_INTERNAL_UNREF(&exec_ctx, alarm->cq, "alarm");
-  gpr_free(alarm);
-  grpc_exec_ctx_finish(&exec_ctx);
+  GRPC_ALARM_UNREF(alarm, "alarm_destroy");
 }
diff --git a/src/core/lib/surface/alarm_internal.h b/src/core/lib/surface/alarm_internal.h
new file mode 100644
index 0000000..7f2126c
--- /dev/null
+++ b/src/core/lib/surface/alarm_internal.h
@@ -0,0 +1,40 @@
+/*
+ *
+ * Copyright 2015-2017 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+#ifndef GRPC_CORE_LIB_SURFACE_ALARM_INTERNAL_H
+#define GRPC_CORE_LIB_SURFACE_ALARM_INTERNAL_H
+
+#include <grpc/support/log.h>
+#include "src/core/lib/debug/trace.h"
+
+#ifndef NDEBUG
+
+extern grpc_tracer_flag grpc_trace_alarm_refcount;
+
+#define GRPC_ALARM_REF(a, reason) alarm_ref_dbg(a, reason, __FILE__, __LINE__)
+#define GRPC_ALARM_UNREF(a, reason) \
+  alarm_unref_dbg(a, reason, __FILE__, __LINE__)
+
+#else /* !defined(NDEBUG) */
+
+#define GRPC_ALARM_REF(a, reason) alarm_ref(a)
+#define GRPC_ALARM_UNREF(a, reason) alarm_unref(a)
+
+#endif /* defined(NDEBUG) */
+
+#endif /* GRPC_CORE_LIB_SURFACE_ALARM_INTERNAL_H */
diff --git a/src/core/lib/surface/completion_queue.c b/src/core/lib/surface/completion_queue.c
index 3d82a32..c20cfbc 100644
--- a/src/core/lib/surface/completion_queue.c
+++ b/src/core/lib/surface/completion_queue.c
@@ -235,7 +235,8 @@
   /* Number of outstanding events (+1 if not shut down) */
   gpr_atm pending_events;
 
-  int shutdown_called;
+  /** 0 initially. 1 once we initiated shutdown */
+  bool shutdown_called;
 } cq_next_data;
 
 typedef struct cq_pluck_data {
@@ -244,15 +245,20 @@
   grpc_cq_completion *completed_tail;
 
   /** Number of pending events (+1 if we're not shutdown) */
-  gpr_refcount pending_events;
+  gpr_atm pending_events;
 
   /** Counter of how many things have ever been queued on this completion queue
       useful for avoiding locks to check the queue */
   gpr_atm things_queued_ever;
 
-  /** 0 initially, 1 once we've begun shutting down */
+  /** 0 initially. 1 once we completed shutting */
+  /* TODO: (sreek) This is not needed since (shutdown == 1) if and only if
+   * (pending_events == 0). So consider removing this in future and use
+   * pending_events */
   gpr_atm shutdown;
-  int shutdown_called;
+
+  /** 0 initially. 1 once we initiated shutdown */
+  bool shutdown_called;
 
   int num_pluckers;
   plucker pluckers[GRPC_MAX_COMPLETION_QUEUE_PLUCKERS];
@@ -436,7 +442,7 @@
 
 static void cq_init_next(void *ptr) {
   cq_next_data *cqd = ptr;
-  /* Initial ref is dropped by grpc_completion_queue_shutdown */
+  /* Initial count is dropped by grpc_completion_queue_shutdown */
   gpr_atm_no_barrier_store(&cqd->pending_events, 1);
   cqd->shutdown_called = false;
   gpr_atm_no_barrier_store(&cqd->things_queued_ever, 0);
@@ -451,12 +457,12 @@
 
 static void cq_init_pluck(void *ptr) {
   cq_pluck_data *cqd = ptr;
-  /* Initial ref is dropped by grpc_completion_queue_shutdown */
-  gpr_ref_init(&cqd->pending_events, 1);
+  /* Initial count is dropped by grpc_completion_queue_shutdown */
+  gpr_atm_no_barrier_store(&cqd->pending_events, 1);
   cqd->completed_tail = &cqd->completed_head;
   cqd->completed_head.next = (uintptr_t)cqd->completed_tail;
   gpr_atm_no_barrier_store(&cqd->shutdown, 0);
-  cqd->shutdown_called = 0;
+  cqd->shutdown_called = false;
   cqd->num_pluckers = 0;
   gpr_atm_no_barrier_store(&cqd->things_queued_ever, 0);
 }
@@ -549,24 +555,32 @@
 static void cq_check_tag(grpc_completion_queue *cq, void *tag, bool lock_cq) {}
 #endif
 
-static bool cq_begin_op_for_next(grpc_completion_queue *cq, void *tag) {
-  cq_next_data *cqd = DATA_FROM_CQ(cq);
+/* Atomically increments a counter only if the counter is not zero. Returns
+ * true if the increment was successful; false if the counter is zero */
+static bool atm_inc_if_nonzero(gpr_atm *counter) {
   while (true) {
-    gpr_atm count = gpr_atm_no_barrier_load(&cqd->pending_events);
+    gpr_atm count = gpr_atm_no_barrier_load(counter);
+    /* If zero, we are done. If not, we must to a CAS (instead of an atomic
+     * increment) to maintain the contract: do not increment the counter if it
+     * is zero. */
     if (count == 0) {
       return false;
-    } else if (gpr_atm_no_barrier_cas(&cqd->pending_events, count, count + 1)) {
+    } else if (gpr_atm_no_barrier_cas(counter, count, count + 1)) {
       break;
     }
   }
+
   return true;
 }
 
+static bool cq_begin_op_for_next(grpc_completion_queue *cq, void *tag) {
+  cq_next_data *cqd = DATA_FROM_CQ(cq);
+  return atm_inc_if_nonzero(&cqd->pending_events);
+}
+
 static bool cq_begin_op_for_pluck(grpc_completion_queue *cq, void *tag) {
   cq_pluck_data *cqd = DATA_FROM_CQ(cq);
-  GPR_ASSERT(!cqd->shutdown_called);
-  gpr_ref(&cqd->pending_events);
-  return true;
+  return atm_inc_if_nonzero(&cqd->pending_events);
 }
 
 bool grpc_cq_begin_op(grpc_completion_queue *cq, void *tag) {
@@ -704,8 +718,10 @@
       ((uintptr_t)storage) | (1u & (uintptr_t)cqd->completed_tail->next);
   cqd->completed_tail = storage;
 
-  int shutdown = gpr_unref(&cqd->pending_events);
-  if (!shutdown) {
+  if (gpr_atm_full_fetch_add(&cqd->pending_events, -1) == 1) {
+    cq_finish_shutdown_pluck(exec_ctx, cq);
+    gpr_mu_unlock(cq->mu);
+  } else {
     grpc_pollset_worker *pluck_worker = NULL;
     for (int i = 0; i < cqd->num_pluckers; i++) {
       if (cqd->pluckers[i].tag == tag) {
@@ -725,9 +741,6 @@
 
       GRPC_ERROR_UNREF(kick_error);
     }
-  } else {
-    cq_finish_shutdown_pluck(exec_ctx, cq);
-    gpr_mu_unlock(cq->mu);
   }
 
   GPR_TIMER_END("cq_end_op_for_pluck", 0);
@@ -952,6 +965,12 @@
                              grpc_completion_queue *cq) {
   cq_next_data *cqd = DATA_FROM_CQ(cq);
 
+  /* Need an extra ref for cq here because:
+   * We call cq_finish_shutdown_next() below, that would call pollset shutdown.
+   * Pollset shutdown decrements the cq ref count which can potentially destroy
+   * the cq (if that happens to be the last ref).
+   * Creating an extra ref here prevents the cq from getting destroyed while
+   * this function is still active */
   GRPC_CQ_INTERNAL_REF(cq, "shutting_down");
   gpr_mu_lock(cq->mu);
   if (cqd->shutdown_called) {
@@ -960,7 +979,7 @@
     GPR_TIMER_END("grpc_completion_queue_shutdown", 0);
     return;
   }
-  cqd->shutdown_called = 1;
+  cqd->shutdown_called = true;
   if (gpr_atm_full_fetch_add(&cqd->pending_events, -1) == 1) {
     cq_finish_shutdown_next(exec_ctx, cq);
   }
@@ -1172,21 +1191,32 @@
                               &cq->pollset_shutdown_done);
 }
 
+/* NOTE: This function is almost exactly identical to cq_shutdown_next() but
+ * merging them is a bit tricky and probably not worth it */
 static void cq_shutdown_pluck(grpc_exec_ctx *exec_ctx,
                               grpc_completion_queue *cq) {
   cq_pluck_data *cqd = DATA_FROM_CQ(cq);
 
+  /* Need an extra ref for cq here because:
+   * We call cq_finish_shutdown_pluck() below, that would call pollset shutdown.
+   * Pollset shutdown decrements the cq ref count which can potentially destroy
+   * the cq (if that happens to be the last ref).
+   * Creating an extra ref here prevents the cq from getting destroyed while
+   * this function is still active */
+  GRPC_CQ_INTERNAL_REF(cq, "shutting_down (pluck cq)");
   gpr_mu_lock(cq->mu);
   if (cqd->shutdown_called) {
     gpr_mu_unlock(cq->mu);
+    GRPC_CQ_INTERNAL_UNREF(exec_ctx, cq, "shutting_down (pluck cq)");
     GPR_TIMER_END("grpc_completion_queue_shutdown", 0);
     return;
   }
-  cqd->shutdown_called = 1;
-  if (gpr_unref(&cqd->pending_events)) {
+  cqd->shutdown_called = true;
+  if (gpr_atm_full_fetch_add(&cqd->pending_events, -1) == 1) {
     cq_finish_shutdown_pluck(exec_ctx, cq);
   }
   gpr_mu_unlock(cq->mu);
+  GRPC_CQ_INTERNAL_UNREF(exec_ctx, cq, "shutting_down (pluck cq)");
 }
 
 /* Shutdown simply drops a ref that we reserved at creation time; if we drop
diff --git a/src/core/lib/surface/init.c b/src/core/lib/surface/init.c
index db111e5..d199ac0 100644
--- a/src/core/lib/surface/init.c
+++ b/src/core/lib/surface/init.c
@@ -36,6 +36,7 @@
 #include "src/core/lib/iomgr/resource_quota.h"
 #include "src/core/lib/profiling/timers.h"
 #include "src/core/lib/slice/slice_internal.h"
+#include "src/core/lib/surface/alarm_internal.h"
 #include "src/core/lib/surface/api_trace.h"
 #include "src/core/lib/surface/call.h"
 #include "src/core/lib/surface/channel_init.h"
@@ -135,6 +136,7 @@
     grpc_register_tracer(&grpc_call_error_trace);
 #ifndef NDEBUG
     grpc_register_tracer(&grpc_trace_pending_tags);
+    grpc_register_tracer(&grpc_trace_alarm_refcount);
     grpc_register_tracer(&grpc_trace_cq_refcount);
     grpc_register_tracer(&grpc_trace_closure);
     grpc_register_tracer(&grpc_trace_error_refcount);
diff --git a/src/core/tsi/fake_transport_security.c b/src/core/tsi/fake_transport_security.c
index 8104473..967126e 100644
--- a/src/core/tsi/fake_transport_security.c
+++ b/src/core/tsi/fake_transport_security.c
@@ -407,8 +407,10 @@
 
 static const tsi_handshaker_result_vtable handshaker_result_vtable = {
     fake_handshaker_result_extract_peer,
+    NULL, /* create_zero_copy_grpc_protector */
     fake_handshaker_result_create_frame_protector,
-    fake_handshaker_result_get_unused_bytes, fake_handshaker_result_destroy,
+    fake_handshaker_result_get_unused_bytes,
+    fake_handshaker_result_destroy,
 };
 
 static tsi_result fake_handshaker_result_create(
@@ -530,7 +532,7 @@
 
 static tsi_result fake_handshaker_next(
     tsi_handshaker *self, const unsigned char *received_bytes,
-    size_t received_bytes_size, unsigned char **bytes_to_send,
+    size_t received_bytes_size, const unsigned char **bytes_to_send,
     size_t *bytes_to_send_size, tsi_handshaker_result **handshaker_result,
     tsi_handshaker_on_next_done_cb cb, void *user_data) {
   /* Sanity check the arguments. */
diff --git a/src/core/tsi/transport_security.c b/src/core/tsi/transport_security.c
index 2b1f431..7621307 100644
--- a/src/core/tsi/transport_security.c
+++ b/src/core/tsi/transport_security.c
@@ -74,14 +74,12 @@
                                        size_t *unprotected_bytes_size,
                                        unsigned char *protected_output_frames,
                                        size_t *protected_output_frames_size) {
-  if (self == NULL || unprotected_bytes == NULL ||
+  if (self == NULL || self->vtable == NULL || unprotected_bytes == NULL ||
       unprotected_bytes_size == NULL || protected_output_frames == NULL ||
       protected_output_frames_size == NULL) {
     return TSI_INVALID_ARGUMENT;
   }
-  if (self->vtable == NULL || self->vtable->protect == NULL) {
-    return TSI_UNIMPLEMENTED;
-  }
+  if (self->vtable->protect == NULL) return TSI_UNIMPLEMENTED;
   return self->vtable->protect(self, unprotected_bytes, unprotected_bytes_size,
                                protected_output_frames,
                                protected_output_frames_size);
@@ -90,13 +88,11 @@
 tsi_result tsi_frame_protector_protect_flush(
     tsi_frame_protector *self, unsigned char *protected_output_frames,
     size_t *protected_output_frames_size, size_t *still_pending_size) {
-  if (self == NULL || protected_output_frames == NULL ||
+  if (self == NULL || self->vtable == NULL || protected_output_frames == NULL ||
       protected_output_frames_size == NULL || still_pending_size == NULL) {
     return TSI_INVALID_ARGUMENT;
   }
-  if (self->vtable == NULL || self->vtable->protect_flush == NULL) {
-    return TSI_UNIMPLEMENTED;
-  }
+  if (self->vtable->protect_flush == NULL) return TSI_UNIMPLEMENTED;
   return self->vtable->protect_flush(self, protected_output_frames,
                                      protected_output_frames_size,
                                      still_pending_size);
@@ -106,14 +102,12 @@
     tsi_frame_protector *self, const unsigned char *protected_frames_bytes,
     size_t *protected_frames_bytes_size, unsigned char *unprotected_bytes,
     size_t *unprotected_bytes_size) {
-  if (self == NULL || protected_frames_bytes == NULL ||
+  if (self == NULL || self->vtable == NULL || protected_frames_bytes == NULL ||
       protected_frames_bytes_size == NULL || unprotected_bytes == NULL ||
       unprotected_bytes_size == NULL) {
     return TSI_INVALID_ARGUMENT;
   }
-  if (self->vtable == NULL || self->vtable->unprotect == NULL) {
-    return TSI_UNIMPLEMENTED;
-  }
+  if (self->vtable->unprotect == NULL) return TSI_UNIMPLEMENTED;
   return self->vtable->unprotect(self, protected_frames_bytes,
                                  protected_frames_bytes_size, unprotected_bytes,
                                  unprotected_bytes_size);
@@ -131,48 +125,44 @@
 tsi_result tsi_handshaker_get_bytes_to_send_to_peer(tsi_handshaker *self,
                                                     unsigned char *bytes,
                                                     size_t *bytes_size) {
-  if (self == NULL || bytes == NULL || bytes_size == NULL) {
+  if (self == NULL || self->vtable == NULL || bytes == NULL ||
+      bytes_size == NULL) {
     return TSI_INVALID_ARGUMENT;
   }
   if (self->frame_protector_created) return TSI_FAILED_PRECONDITION;
-  if (self->vtable == NULL || self->vtable->get_bytes_to_send_to_peer == NULL) {
-    return TSI_UNIMPLEMENTED;
-  }
+  if (self->vtable->get_bytes_to_send_to_peer == NULL) return TSI_UNIMPLEMENTED;
   return self->vtable->get_bytes_to_send_to_peer(self, bytes, bytes_size);
 }
 
 tsi_result tsi_handshaker_process_bytes_from_peer(tsi_handshaker *self,
                                                   const unsigned char *bytes,
                                                   size_t *bytes_size) {
-  if (self == NULL || bytes == NULL || bytes_size == NULL) {
+  if (self == NULL || self->vtable == NULL || bytes == NULL ||
+      bytes_size == NULL) {
     return TSI_INVALID_ARGUMENT;
   }
   if (self->frame_protector_created) return TSI_FAILED_PRECONDITION;
-  if (self->vtable == NULL || self->vtable->process_bytes_from_peer == NULL) {
-    return TSI_UNIMPLEMENTED;
-  }
+  if (self->vtable->process_bytes_from_peer == NULL) return TSI_UNIMPLEMENTED;
   return self->vtable->process_bytes_from_peer(self, bytes, bytes_size);
 }
 
 tsi_result tsi_handshaker_get_result(tsi_handshaker *self) {
-  if (self == NULL) return TSI_INVALID_ARGUMENT;
+  if (self == NULL || self->vtable == NULL) return TSI_INVALID_ARGUMENT;
   if (self->frame_protector_created) return TSI_FAILED_PRECONDITION;
-  if (self->vtable == NULL || self->vtable->get_result == NULL) {
-    return TSI_UNIMPLEMENTED;
-  }
+  if (self->vtable->get_result == NULL) return TSI_UNIMPLEMENTED;
   return self->vtable->get_result(self);
 }
 
 tsi_result tsi_handshaker_extract_peer(tsi_handshaker *self, tsi_peer *peer) {
-  if (self == NULL || peer == NULL) return TSI_INVALID_ARGUMENT;
+  if (self == NULL || self->vtable == NULL || peer == NULL) {
+    return TSI_INVALID_ARGUMENT;
+  }
   memset(peer, 0, sizeof(tsi_peer));
   if (self->frame_protector_created) return TSI_FAILED_PRECONDITION;
   if (tsi_handshaker_get_result(self) != TSI_OK) {
     return TSI_FAILED_PRECONDITION;
   }
-  if (self->vtable == NULL || self->vtable->extract_peer == NULL) {
-    return TSI_UNIMPLEMENTED;
-  }
+  if (self->vtable->extract_peer == NULL) return TSI_UNIMPLEMENTED;
   return self->vtable->extract_peer(self, peer);
 }
 
@@ -180,14 +170,12 @@
     tsi_handshaker *self, size_t *max_protected_frame_size,
     tsi_frame_protector **protector) {
   tsi_result result;
-  if (self == NULL || protector == NULL) return TSI_INVALID_ARGUMENT;
+  if (self == NULL || self->vtable == NULL || protector == NULL) {
+    return TSI_INVALID_ARGUMENT;
+  }
   if (self->frame_protector_created) return TSI_FAILED_PRECONDITION;
-  if (tsi_handshaker_get_result(self) != TSI_OK) {
-    return TSI_FAILED_PRECONDITION;
-  }
-  if (self->vtable == NULL || self->vtable->create_frame_protector == NULL) {
-    return TSI_UNIMPLEMENTED;
-  }
+  if (tsi_handshaker_get_result(self) != TSI_OK) return TSI_FAILED_PRECONDITION;
+  if (self->vtable->create_frame_protector == NULL) return TSI_UNIMPLEMENTED;
   result = self->vtable->create_frame_protector(self, max_protected_frame_size,
                                                 protector);
   if (result == TSI_OK) {
@@ -198,14 +186,12 @@
 
 tsi_result tsi_handshaker_next(
     tsi_handshaker *self, const unsigned char *received_bytes,
-    size_t received_bytes_size, unsigned char **bytes_to_send,
+    size_t received_bytes_size, const unsigned char **bytes_to_send,
     size_t *bytes_to_send_size, tsi_handshaker_result **handshaker_result,
     tsi_handshaker_on_next_done_cb cb, void *user_data) {
-  if (self == NULL) return TSI_INVALID_ARGUMENT;
+  if (self == NULL || self->vtable == NULL) return TSI_INVALID_ARGUMENT;
   if (self->handshaker_result_created) return TSI_FAILED_PRECONDITION;
-  if (self->vtable == NULL || self->vtable->next == NULL) {
-    return TSI_UNIMPLEMENTED;
-  }
+  if (self->vtable->next == NULL) return TSI_UNIMPLEMENTED;
   return self->vtable->next(self, received_bytes, received_bytes_size,
                             bytes_to_send, bytes_to_send_size,
                             handshaker_result, cb, user_data);
@@ -220,21 +206,21 @@
 
 tsi_result tsi_handshaker_result_extract_peer(const tsi_handshaker_result *self,
                                               tsi_peer *peer) {
-  if (self == NULL || peer == NULL) return TSI_INVALID_ARGUMENT;
-  memset(peer, 0, sizeof(tsi_peer));
-  if (self->vtable == NULL || self->vtable->extract_peer == NULL) {
-    return TSI_UNIMPLEMENTED;
+  if (self == NULL || self->vtable == NULL || peer == NULL) {
+    return TSI_INVALID_ARGUMENT;
   }
+  memset(peer, 0, sizeof(tsi_peer));
+  if (self->vtable->extract_peer == NULL) return TSI_UNIMPLEMENTED;
   return self->vtable->extract_peer(self, peer);
 }
 
 tsi_result tsi_handshaker_result_create_frame_protector(
     const tsi_handshaker_result *self, size_t *max_protected_frame_size,
     tsi_frame_protector **protector) {
-  if (self == NULL || protector == NULL) return TSI_INVALID_ARGUMENT;
-  if (self->vtable == NULL || self->vtable->create_frame_protector == NULL) {
-    return TSI_UNIMPLEMENTED;
+  if (self == NULL || self->vtable == NULL || protector == NULL) {
+    return TSI_INVALID_ARGUMENT;
   }
+  if (self->vtable->create_frame_protector == NULL) return TSI_UNIMPLEMENTED;
   return self->vtable->create_frame_protector(self, max_protected_frame_size,
                                               protector);
 }
@@ -242,12 +228,11 @@
 tsi_result tsi_handshaker_result_get_unused_bytes(
     const tsi_handshaker_result *self, const unsigned char **bytes,
     size_t *bytes_size) {
-  if (self == NULL || bytes == NULL || bytes_size == NULL) {
+  if (self == NULL || self->vtable == NULL || bytes == NULL ||
+      bytes_size == NULL) {
     return TSI_INVALID_ARGUMENT;
   }
-  if (self->vtable == NULL || self->vtable->get_unused_bytes == NULL) {
-    return TSI_UNIMPLEMENTED;
-  }
+  if (self->vtable->get_unused_bytes == NULL) return TSI_UNIMPLEMENTED;
   return self->vtable->get_unused_bytes(self, bytes, bytes_size);
 }
 
diff --git a/src/core/tsi/transport_security.h b/src/core/tsi/transport_security.h
index 2c7db6b..b0d7039 100644
--- a/src/core/tsi/transport_security.h
+++ b/src/core/tsi/transport_security.h
@@ -70,7 +70,8 @@
                                        tsi_frame_protector **protector);
   void (*destroy)(tsi_handshaker *self);
   tsi_result (*next)(tsi_handshaker *self, const unsigned char *received_bytes,
-                     size_t received_bytes_size, unsigned char **bytes_to_send,
+                     size_t received_bytes_size,
+                     const unsigned char **bytes_to_send,
                      size_t *bytes_to_send_size,
                      tsi_handshaker_result **handshaker_result,
                      tsi_handshaker_on_next_done_cb cb, void *user_data);
@@ -86,6 +87,10 @@
    See transport_security_interface.h for documentation. */
 typedef struct {
   tsi_result (*extract_peer)(const tsi_handshaker_result *self, tsi_peer *peer);
+  tsi_result (*create_zero_copy_grpc_protector)(
+      const tsi_handshaker_result *self,
+      size_t *max_output_protected_frame_size,
+      tsi_zero_copy_grpc_protector **protector);
   tsi_result (*create_frame_protector)(const tsi_handshaker_result *self,
                                        size_t *max_output_protected_frame_size,
                                        tsi_frame_protector **protector);
diff --git a/src/core/tsi/transport_security_adapter.c b/src/core/tsi/transport_security_adapter.c
index b6dc660..1c2a57b 100644
--- a/src/core/tsi/transport_security_adapter.c
+++ b/src/core/tsi/transport_security_adapter.c
@@ -66,8 +66,11 @@
 }
 
 static const tsi_handshaker_result_vtable result_vtable = {
-    adapter_result_extract_peer, adapter_result_create_frame_protector,
-    adapter_result_get_unused_bytes, adapter_result_destroy,
+    adapter_result_extract_peer,
+    NULL, /* create_zero_copy_grpc_protector */
+    adapter_result_create_frame_protector,
+    adapter_result_get_unused_bytes,
+    adapter_result_destroy,
 };
 
 /* Ownership of wrapped tsi_handshaker is transferred to the result object.  */
@@ -140,7 +143,7 @@
 
 static tsi_result adapter_next(
     tsi_handshaker *self, const unsigned char *received_bytes,
-    size_t received_bytes_size, unsigned char **bytes_to_send,
+    size_t received_bytes_size, const unsigned char **bytes_to_send,
     size_t *bytes_to_send_size, tsi_handshaker_result **handshaker_result,
     tsi_handshaker_on_next_done_cb cb, void *user_data) {
   /* Input sanity check.  */
diff --git a/src/core/tsi/transport_security_grpc.c b/src/core/tsi/transport_security_grpc.c
new file mode 100644
index 0000000..5bcfdfa
--- /dev/null
+++ b/src/core/tsi/transport_security_grpc.c
@@ -0,0 +1,64 @@
+/*
+ *
+ * Copyright 2017 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+#include "src/core/tsi/transport_security_grpc.h"
+
+/* This method creates a tsi_zero_copy_grpc_protector object.  */
+tsi_result tsi_handshaker_result_create_zero_copy_grpc_protector(
+    const tsi_handshaker_result *self, size_t *max_output_protected_frame_size,
+    tsi_zero_copy_grpc_protector **protector) {
+  if (self == NULL || self->vtable == NULL || protector == NULL) {
+    return TSI_INVALID_ARGUMENT;
+  }
+  if (self->vtable->create_zero_copy_grpc_protector == NULL) {
+    return TSI_UNIMPLEMENTED;
+  }
+  return self->vtable->create_zero_copy_grpc_protector(
+      self, max_output_protected_frame_size, protector);
+}
+
+/* --- tsi_zero_copy_grpc_protector common implementation. ---
+
+   Calls specific implementation after state/input validation. */
+
+tsi_result tsi_zero_copy_grpc_protector_protect(
+    tsi_zero_copy_grpc_protector *self, grpc_slice_buffer *unprotected_slices,
+    grpc_slice_buffer *protected_slices) {
+  if (self == NULL || self->vtable == NULL || unprotected_slices == NULL ||
+      protected_slices == NULL) {
+    return TSI_INVALID_ARGUMENT;
+  }
+  if (self->vtable->protect == NULL) return TSI_UNIMPLEMENTED;
+  return self->vtable->protect(self, unprotected_slices, protected_slices);
+}
+
+tsi_result tsi_zero_copy_grpc_protector_unprotect(
+    tsi_zero_copy_grpc_protector *self, grpc_slice_buffer *protected_slices,
+    grpc_slice_buffer *unprotected_slices) {
+  if (self == NULL || self->vtable == NULL || protected_slices == NULL ||
+      unprotected_slices == NULL) {
+    return TSI_INVALID_ARGUMENT;
+  }
+  if (self->vtable->unprotect == NULL) return TSI_UNIMPLEMENTED;
+  return self->vtable->unprotect(self, protected_slices, unprotected_slices);
+}
+
+void tsi_zero_copy_grpc_protector_destroy(tsi_zero_copy_grpc_protector *self) {
+  if (self == NULL) return;
+  self->vtable->destroy(self);
+}
diff --git a/src/core/tsi/transport_security_grpc.h b/src/core/tsi/transport_security_grpc.h
new file mode 100644
index 0000000..5ab5297
--- /dev/null
+++ b/src/core/tsi/transport_security_grpc.h
@@ -0,0 +1,80 @@
+/*
+ *
+ * Copyright 2017 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+#ifndef GRPC_CORE_TSI_TRANSPORT_SECURITY_GRPC_H
+#define GRPC_CORE_TSI_TRANSPORT_SECURITY_GRPC_H
+
+#include <grpc/slice_buffer.h>
+#include "src/core/tsi/transport_security.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/* This method creates a tsi_zero_copy_grpc_protector object. It return TSI_OK
+   assuming there is no fatal error.
+   The caller is responsible for destroying the protector.  */
+tsi_result tsi_handshaker_result_create_zero_copy_grpc_protector(
+    const tsi_handshaker_result *self, size_t *max_output_protected_frame_size,
+    tsi_zero_copy_grpc_protector **protector);
+
+/* -- tsi_zero_copy_grpc_protector object --  */
+
+/* Outputs protected frames.
+   - unprotected_slices is the unprotected data to be protected.
+   - protected_slices is the protected output frames. One or more frames
+     may be produced in this protect function.
+   - This method returns TSI_OK in case of success or a specific error code in
+     case of failure.  */
+tsi_result tsi_zero_copy_grpc_protector_protect(
+    tsi_zero_copy_grpc_protector *self, grpc_slice_buffer *unprotected_slices,
+    grpc_slice_buffer *protected_slices);
+
+/* Outputs unprotected bytes.
+   - protected_slices is the bytes of protected frames.
+   - unprotected_slices is the unprotected output data.
+   - This method returns TSI_OK in case of success. Success includes cases where
+     there is not enough data to output in which case unprotected_slices has 0
+     bytes.  */
+tsi_result tsi_zero_copy_grpc_protector_unprotect(
+    tsi_zero_copy_grpc_protector *self, grpc_slice_buffer *protected_slices,
+    grpc_slice_buffer *unprotected_slices);
+
+/* Destroys the tsi_zero_copy_grpc_protector object.  */
+void tsi_zero_copy_grpc_protector_destroy(tsi_zero_copy_grpc_protector *self);
+
+/* Base for tsi_zero_copy_grpc_protector implementations.  */
+typedef struct {
+  tsi_result (*protect)(tsi_zero_copy_grpc_protector *self,
+                        grpc_slice_buffer *unprotected_slices,
+                        grpc_slice_buffer *protected_slices);
+  tsi_result (*unprotect)(tsi_zero_copy_grpc_protector *self,
+                          grpc_slice_buffer *protected_slices,
+                          grpc_slice_buffer *unprotected_slices);
+  void (*destroy)(tsi_zero_copy_grpc_protector *self);
+} tsi_zero_copy_grpc_protector_vtable;
+
+struct tsi_zero_copy_grpc_protector {
+  const tsi_zero_copy_grpc_protector_vtable *vtable;
+};
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* GRPC_CORE_TSI_TRANSPORT_SECURITY_GRPC_H */
diff --git a/src/core/tsi/transport_security_interface.h b/src/core/tsi/transport_security_interface.h
index 39ba8ad..80c426b 100644
--- a/src/core/tsi/transport_security_interface.h
+++ b/src/core/tsi/transport_security_interface.h
@@ -62,6 +62,15 @@
 
 extern grpc_tracer_flag tsi_tracing_enabled;
 
+/* -- tsi_zero_copy_grpc_protector object --
+
+  This object protects and unprotects grpc slice buffers with zero or minimized
+  memory copy once the handshake is done. Implementations of this object must be
+  thread compatible. This object depends on grpc and the details of this object
+  is defined in transport_security_grpc.h.  */
+
+typedef struct tsi_zero_copy_grpc_protector tsi_zero_copy_grpc_protector;
+
 /* --- tsi_frame_protector object ---
 
   This object protects and unprotects buffers once the handshake is done.
@@ -429,7 +438,7 @@
    tsi_handshaker object.  */
 tsi_result tsi_handshaker_next(
     tsi_handshaker *self, const unsigned char *received_bytes,
-    size_t received_bytes_size, unsigned char **bytes_to_send,
+    size_t received_bytes_size, const unsigned char **bytes_to_send,
     size_t *bytes_to_send_size, tsi_handshaker_result **handshaker_result,
     tsi_handshaker_on_next_done_cb cb, void *user_data);
 
diff --git a/src/cpp/util/slice_cc.cc b/src/cpp/util/slice_cc.cc
index 56e0328..486d0cd 100644
--- a/src/cpp/util/slice_cc.cc
+++ b/src/cpp/util/slice_cc.cc
@@ -17,6 +17,7 @@
  */
 
 #include <grpc++/support/slice.h>
+#include <grpc/slice.h>
 
 namespace grpc {
 
@@ -43,4 +44,10 @@
 
 Slice::Slice(const Slice& other) : slice_(grpc_slice_ref(other.slice_)) {}
 
+Slice::Slice(void* buf, size_t len, void (*destroy)(void*), void* user_data)
+    : slice_(grpc_slice_new_with_user_data(buf, len, destroy, user_data)) {}
+
+Slice::Slice(void* buf, size_t len, void (*destroy)(void*, size_t))
+    : slice_(grpc_slice_new_with_len(buf, len, destroy)) {}
+
 }  // namespace grpc
diff --git a/src/csharp/Grpc.Core.Tests/ClientServerTest.cs b/src/csharp/Grpc.Core.Tests/ClientServerTest.cs
index c74d04c..0cb9288 100644
--- a/src/csharp/Grpc.Core.Tests/ClientServerTest.cs
+++ b/src/csharp/Grpc.Core.Tests/ClientServerTest.cs
@@ -92,9 +92,33 @@
 
             var ex = Assert.Throws<RpcException>(() => Calls.BlockingUnaryCall(helper.CreateUnaryCall(), "abc"));
             Assert.AreEqual(StatusCode.Unauthenticated, ex.Status.StatusCode);
+            Assert.AreEqual(0, ex.Trailers.Count);
 
             var ex2 = Assert.ThrowsAsync<RpcException>(async () => await Calls.AsyncUnaryCall(helper.CreateUnaryCall(), "abc"));
             Assert.AreEqual(StatusCode.Unauthenticated, ex2.Status.StatusCode);
+            Assert.AreEqual(0, ex.Trailers.Count);
+        }
+
+        [Test]
+        public void UnaryCall_ServerHandlerThrowsRpcExceptionWithTrailers()
+        {
+            helper.UnaryHandler = new UnaryServerMethod<string, string>((request, context) =>
+            {
+                var trailers = new Metadata { {"xyz", "xyz-value"} };
+                throw new RpcException(new Status(StatusCode.Unauthenticated, ""), trailers);
+            });
+
+            var ex = Assert.Throws<RpcException>(() => Calls.BlockingUnaryCall(helper.CreateUnaryCall(), "abc"));
+            Assert.AreEqual(StatusCode.Unauthenticated, ex.Status.StatusCode);
+            Assert.AreEqual(1, ex.Trailers.Count);
+            Assert.AreEqual("xyz", ex.Trailers[0].Key);
+            Assert.AreEqual("xyz-value", ex.Trailers[0].Value);
+
+            var ex2 = Assert.ThrowsAsync<RpcException>(async () => await Calls.AsyncUnaryCall(helper.CreateUnaryCall(), "abc"));
+            Assert.AreEqual(StatusCode.Unauthenticated, ex2.Status.StatusCode);
+            Assert.AreEqual(1, ex2.Trailers.Count);
+            Assert.AreEqual("xyz", ex2.Trailers[0].Key);
+            Assert.AreEqual("xyz-value", ex2.Trailers[0].Value);
         }
 
         [Test]
@@ -108,9 +132,34 @@
 
             var ex = Assert.Throws<RpcException>(() => Calls.BlockingUnaryCall(helper.CreateUnaryCall(), "abc"));
             Assert.AreEqual(StatusCode.Unauthenticated, ex.Status.StatusCode);
+            Assert.AreEqual(0, ex.Trailers.Count);
 
             var ex2 = Assert.ThrowsAsync<RpcException>(async () => await Calls.AsyncUnaryCall(helper.CreateUnaryCall(), "abc"));
             Assert.AreEqual(StatusCode.Unauthenticated, ex2.Status.StatusCode);
+            Assert.AreEqual(0, ex2.Trailers.Count);
+        }
+
+        [Test]
+        public void UnaryCall_ServerHandlerSetsStatusAndTrailers()
+        {
+            helper.UnaryHandler = new UnaryServerMethod<string, string>(async (request, context) =>
+            {
+                context.Status = new Status(StatusCode.Unauthenticated, "");
+                context.ResponseTrailers.Add("xyz", "xyz-value");
+                return "";
+            });
+
+            var ex = Assert.Throws<RpcException>(() => Calls.BlockingUnaryCall(helper.CreateUnaryCall(), "abc"));
+            Assert.AreEqual(StatusCode.Unauthenticated, ex.Status.StatusCode);
+            Assert.AreEqual(1, ex.Trailers.Count);
+            Assert.AreEqual("xyz", ex.Trailers[0].Key);
+            Assert.AreEqual("xyz-value", ex.Trailers[0].Value);
+
+            var ex2 = Assert.ThrowsAsync<RpcException>(async () => await Calls.AsyncUnaryCall(helper.CreateUnaryCall(), "abc"));
+            Assert.AreEqual(StatusCode.Unauthenticated, ex2.Status.StatusCode);
+            Assert.AreEqual(1, ex2.Trailers.Count);
+            Assert.AreEqual("xyz", ex2.Trailers[0].Key);
+            Assert.AreEqual("xyz-value", ex2.Trailers[0].Value);
         }
 
         [Test]
@@ -148,7 +197,7 @@
             CollectionAssert.AreEqual(new string[] { "A", "B", "C" }, await call.ResponseStream.ToListAsync());
 
             Assert.AreEqual(StatusCode.OK, call.GetStatus().StatusCode);
-            Assert.IsNotNull("xyz", call.GetTrailers()[0].Key);
+            Assert.AreEqual("xyz", call.GetTrailers()[0].Key);
         }
 
         [Test]
@@ -183,6 +232,27 @@
         }
 
         [Test]
+        public async Task ServerStreamingCall_TrailersFromMultipleSourcesGetConcatenated()
+        {
+            helper.ServerStreamingHandler = new ServerStreamingServerMethod<string, string>(async (request, responseStream, context) =>
+            {
+                context.ResponseTrailers.Add("xyz", "xyz-value");
+                throw new RpcException(new Status(StatusCode.InvalidArgument, ""), new Metadata { {"abc", "abc-value"} });
+            });
+
+            var call = Calls.AsyncServerStreamingCall(helper.CreateServerStreamingCall(), "");
+
+            var ex = Assert.ThrowsAsync<RpcException>(async () => await call.ResponseStream.MoveNext());
+            Assert.AreEqual(StatusCode.InvalidArgument, ex.Status.StatusCode);
+            Assert.AreEqual(2, call.GetTrailers().Count);
+            Assert.AreEqual(2, ex.Trailers.Count);
+            Assert.AreEqual("xyz", ex.Trailers[0].Key);
+            Assert.AreEqual("xyz-value", ex.Trailers[0].Value);
+            Assert.AreEqual("abc", ex.Trailers[1].Key);
+            Assert.AreEqual("abc-value", ex.Trailers[1].Value);
+        }
+
+        [Test]
         public async Task DuplexStreamingCall()
         {
             helper.DuplexStreamingHandler = new DuplexStreamingServerMethod<string, string>(async (requestStream, responseStream, context) =>
@@ -199,7 +269,7 @@
             CollectionAssert.AreEqual(new string[] { "A", "B", "C" }, await call.ResponseStream.ToListAsync());
 
             Assert.AreEqual(StatusCode.OK, call.GetStatus().StatusCode);
-            Assert.IsNotNull("xyz-value", call.GetTrailers()[0].Value);
+            Assert.AreEqual("xyz-value", call.GetTrailers()[0].Value);
         }
 
         [Test]
diff --git a/src/csharp/Grpc.Core.Tests/GrpcEnvironmentTest.cs b/src/csharp/Grpc.Core.Tests/GrpcEnvironmentTest.cs
index 0f3a82c..fc9d559 100644
--- a/src/csharp/Grpc.Core.Tests/GrpcEnvironmentTest.cs
+++ b/src/csharp/Grpc.Core.Tests/GrpcEnvironmentTest.cs
@@ -18,6 +18,7 @@
 
 using System;
 using System.Linq;
+using System.Threading;
 using Grpc.Core;
 using NUnit.Framework;
 
@@ -75,5 +76,19 @@
             var parts = coreVersion.Split('.');
             Assert.AreEqual(3, parts.Length);
         }
+
+        [Test]
+        public void ShuttingDownEventIsFired()
+        {
+            var cts = new CancellationTokenSource();
+            var handler = new EventHandler((sender, args) => { cts.Cancel(); });
+            
+            GrpcEnvironment.ShuttingDown += handler;
+            var env = GrpcEnvironment.AddRef();
+            GrpcEnvironment.ReleaseAsync().Wait();
+            GrpcEnvironment.ShuttingDown -= handler;
+            
+            Assert.IsTrue(cts.Token.IsCancellationRequested);
+        }
     }
 }
diff --git a/src/csharp/Grpc.Core/GrpcEnvironment.cs b/src/csharp/Grpc.Core/GrpcEnvironment.cs
index 0663ee9..cbc7d20 100644
--- a/src/csharp/Grpc.Core/GrpcEnvironment.cs
+++ b/src/csharp/Grpc.Core/GrpcEnvironment.cs
@@ -49,7 +49,7 @@
         readonly DebugStats debugStats = new DebugStats();
         readonly AtomicCounter cqPickerCounter = new AtomicCounter();
 
-        bool isClosed;
+        bool isShutdown;
 
         /// <summary>
         /// Returns a reference-counted instance of initialized gRPC environment.
@@ -238,6 +238,12 @@
         }
 
         /// <summary>
+        /// Occurs when <c>GrpcEnvironment</c> is about the start the shutdown logic.
+        /// If <c>GrpcEnvironment</c> is later initialized and shutdown, the event will be fired again (unless unregistered first).
+        /// </summary>
+        public static event EventHandler ShuttingDown;
+
+        /// <summary>
         /// Creates gRPC environment.
         /// </summary>
         private GrpcEnvironment()
@@ -311,13 +317,16 @@
         /// </summary>
         private async Task ShutdownAsync()
         {
-            if (isClosed)
+            if (isShutdown)
             {
-                throw new InvalidOperationException("Close has already been called");
+                throw new InvalidOperationException("ShutdownAsync has already been called");
             }
+
+            await Task.Run(() => ShuttingDown?.Invoke(this, null)).ConfigureAwait(false);
+
             await threadPool.StopAsync().ConfigureAwait(false);
             GrpcNativeShutdown();
-            isClosed = true;
+            isShutdown = true;
 
             debugStats.CheckOK();
         }
diff --git a/src/csharp/Grpc.Core/Internal/AsyncCall.cs b/src/csharp/Grpc.Core/Internal/AsyncCall.cs
index 6e6ca7c..17109de 100644
--- a/src/csharp/Grpc.Core/Internal/AsyncCall.cs
+++ b/src/csharp/Grpc.Core/Internal/AsyncCall.cs
@@ -329,7 +329,7 @@
 
         protected override Exception GetRpcExceptionClientOnly()
         {
-            return new RpcException(finishedStatus.Value.Status);
+            return new RpcException(finishedStatus.Value.Status, finishedStatus.Value.Trailers);
         }
 
         protected override Task CheckSendAllowedOrEarlyResult()
@@ -348,7 +348,7 @@
                 // Writing after the call has finished is not a programming error because server can close
                 // the call anytime, so don't throw directly, but let the write task finish with an error.
                 var tcs = new TaskCompletionSource<object>();
-                tcs.SetException(new RpcException(finishedStatus.Value.Status));
+                tcs.SetException(new RpcException(finishedStatus.Value.Status, finishedStatus.Value.Trailers));
                 return tcs.Task;
             }
 
@@ -468,7 +468,7 @@
             var status = receivedStatus.Status;
             if (status.StatusCode != StatusCode.OK)
             {
-                unaryResponseTcs.SetException(new RpcException(status));
+                unaryResponseTcs.SetException(new RpcException(status, receivedStatus.Trailers));
                 return;
             }
 
@@ -506,7 +506,7 @@
             var status = receivedStatus.Status;
             if (status.StatusCode != StatusCode.OK)
             {
-                streamingResponseCallFinishedTcs.SetException(new RpcException(status));
+                streamingResponseCallFinishedTcs.SetException(new RpcException(status, receivedStatus.Trailers));
                 return;
             }
 
diff --git a/src/csharp/Grpc.Core/Internal/ServerCallHandler.cs b/src/csharp/Grpc.Core/Internal/ServerCallHandler.cs
index 36702a3..6019f8e 100644
--- a/src/csharp/Grpc.Core/Internal/ServerCallHandler.cs
+++ b/src/csharp/Grpc.Core/Internal/ServerCallHandler.cs
@@ -76,7 +76,7 @@
                 {
                     Logger.Warning(e, "Exception occured in handler.");
                 }
-                status = HandlerUtils.StatusFromException(e);
+                status = HandlerUtils.GetStatusFromExceptionAndMergeTrailers(e, context.ResponseTrailers);
             }
             try
             {
@@ -133,7 +133,7 @@
                 {
                     Logger.Warning(e, "Exception occured in handler.");
                 }
-                status = HandlerUtils.StatusFromException(e);
+                status = HandlerUtils.GetStatusFromExceptionAndMergeTrailers(e, context.ResponseTrailers);
             }
 
             try
@@ -191,7 +191,7 @@
                 {
                     Logger.Warning(e, "Exception occured in handler.");
                 }
-                status = HandlerUtils.StatusFromException(e);
+                status = HandlerUtils.GetStatusFromExceptionAndMergeTrailers(e, context.ResponseTrailers);
             }
 
             try
@@ -247,7 +247,7 @@
                 {
                     Logger.Warning(e, "Exception occured in handler.");
                 }
-                status = HandlerUtils.StatusFromException(e);
+                status = HandlerUtils.GetStatusFromExceptionAndMergeTrailers(e, context.ResponseTrailers);
             }
             try
             {
@@ -292,11 +292,20 @@
 
     internal static class HandlerUtils
     {
-        public static Status StatusFromException(Exception e)
+        public static Status GetStatusFromExceptionAndMergeTrailers(Exception e, Metadata callContextResponseTrailers)
         {
             var rpcException = e as RpcException;
             if (rpcException != null)
             {
+                // There are two sources of metadata entries on the server-side:
+                // 1. serverCallContext.ResponseTrailers
+                // 2. trailers in RpcException thrown by user code in server side handler.
+                // As metadata allows duplicate keys, the logical thing to do is
+                // to just merge trailers from RpcException into serverCallContext.ResponseTrailers.
+                foreach (var entry in rpcException.Trailers)
+                {
+                    callContextResponseTrailers.Add(entry);
+                }
                 // use the status thrown by handler.
                 return rpcException.Status;
             }
diff --git a/src/csharp/Grpc.Core/RpcException.cs b/src/csharp/Grpc.Core/RpcException.cs
index 01b9e4f..d2c912e 100644
--- a/src/csharp/Grpc.Core/RpcException.cs
+++ b/src/csharp/Grpc.Core/RpcException.cs
@@ -17,6 +17,7 @@
 #endregion
 
 using System;
+using Grpc.Core.Utils;
 
 namespace Grpc.Core
 {
@@ -26,6 +27,7 @@
     public class RpcException : Exception
     {
         private readonly Status status;
+        private readonly Metadata trailers;
 
         /// <summary>
         /// Creates a new <c>RpcException</c> associated with given status.
@@ -34,6 +36,7 @@
         public RpcException(Status status) : base(status.ToString())
         {
             this.status = status;
+            this.trailers = Metadata.Empty;
         }
 
         /// <summary>
@@ -44,6 +47,18 @@
         public RpcException(Status status, string message) : base(message)
         {
             this.status = status;
+            this.trailers = Metadata.Empty;
+        }
+
+        /// <summary>
+        /// Creates a new <c>RpcException</c> associated with given status and trailing response metadata.
+        /// </summary>
+        /// <param name="status">Resulting status of a call.</param>
+        /// <param name="trailers">Response trailing metadata.</param> 
+        public RpcException(Status status, Metadata trailers) : base(status.ToString())
+        {
+            this.status = status;
+            this.trailers = GrpcPreconditions.CheckNotNull(trailers);
         }
 
         /// <summary>
@@ -56,5 +71,18 @@
                 return status;
             }
         }
+
+        /// <summary>
+        /// Gets the call trailing metadata.
+        /// Trailers only have meaningful content for client-side calls (in which case they represent the trailing metadata sent by the server when closing the call).
+        /// Instances of <c>RpcException</c> thrown by the server-side part of the stack will have trailers always set to empty.
+        /// </summary>
+        public Metadata Trailers
+        {
+            get
+            {
+                return trailers;
+            }
+        }
     }
 }
diff --git a/src/csharp/Grpc.IntegrationTesting/CustomErrorDetailsTest.cs b/src/csharp/Grpc.IntegrationTesting/CustomErrorDetailsTest.cs
index be996f9..374c6fc 100644
--- a/src/csharp/Grpc.IntegrationTesting/CustomErrorDetailsTest.cs
+++ b/src/csharp/Grpc.IntegrationTesting/CustomErrorDetailsTest.cs
@@ -65,7 +65,7 @@
         }
 
         [Test]
-        public async Task UnaryCall()
+        public async Task ErrorDetailsFromCallObject()
         {
             var call = client.UnaryCallAsync(new SimpleRequest { ResponseSize = 10 });
 
@@ -83,7 +83,24 @@
             }
         }
 
-        private DebugInfo GetDebugInfo(Metadata trailers)
+        [Test]
+        public async Task ErrorDetailsFromRpcException()
+        {
+            try
+            {
+                await client.UnaryCallAsync(new SimpleRequest { ResponseSize = 10 });
+                Assert.Fail();
+            }
+            catch (RpcException e)
+            {
+                Assert.AreEqual(StatusCode.Unknown, e.Status.StatusCode);
+                var debugInfo = GetDebugInfo(e.Trailers);
+                Assert.AreEqual(debugInfo.Detail, ExceptionDetail);
+                Assert.IsNotEmpty(debugInfo.StackEntries);
+            }
+        }
+
+        private static DebugInfo GetDebugInfo(Metadata trailers)
         {
             var entry = trailers.First((e) => e.Key == DebugInfoTrailerName);
             return DebugInfo.Parser.ParseFrom(entry.ValueBytes);
diff --git a/src/node/ext/call.cc b/src/node/ext/call.cc
index 71e6904..26095a7 100644
--- a/src/node/ext/call.cc
+++ b/src/node/ext/call.cc
@@ -260,7 +260,10 @@
 
 class SendServerStatusOp : public Op {
  public:
-  SendServerStatusOp() { grpc_metadata_array_init(&status_metadata); }
+  SendServerStatusOp() {
+    details = grpc_empty_slice();
+    grpc_metadata_array_init(&status_metadata);
+  }
   ~SendServerStatusOp() {
     grpc_slice_unref(details);
     DestroyMetadataArray(&status_metadata);
@@ -381,7 +384,10 @@
 
 class ClientStatusOp : public Op {
  public:
-  ClientStatusOp() { grpc_metadata_array_init(&metadata_array); }
+  ClientStatusOp() {
+    grpc_metadata_array_init(&metadata_array);
+    status_details = grpc_empty_slice();
+  }
 
   ~ClientStatusOp() {
     grpc_metadata_array_destroy(&metadata_array);
diff --git a/src/node/test/call_test.js b/src/node/test/call_test.js
index aebd298..b5246c4 100644
--- a/src/node/test/call_test.js
+++ b/src/node/test/call_test.js
@@ -188,6 +188,103 @@
       }, TypeError);
     });
   });
+  describe('startBatch with message', function() {
+    it('should fail with null argument', function() {
+      var call = new grpc.Call(channel, 'method', getDeadline(1));
+      assert.throws(function() {
+        var batch = {};
+        batch[grpc.opType.SEND_MESSAGE] = null;
+        call.startBatch(batch, function(){});
+      }, TypeError);
+    });
+    it('should fail with numeric argument', function() {
+      var call = new grpc.Call(channel, 'method', getDeadline(1));
+      assert.throws(function() {
+        var batch = {};
+        batch[grpc.opType.SEND_MESSAGE] = 5;
+        call.startBatch(batch, function(){});
+      }, TypeError);
+    });
+    it('should fail with string argument', function() {
+      var call = new grpc.Call(channel, 'method', getDeadline(1));
+      assert.throws(function() {
+        var batch = {};
+        batch[grpc.opType.SEND_MESSAGE] = 'value';
+        call.startBatch(batch, function(){});
+      }, TypeError);
+    });
+  });
+  describe('startBatch with status', function() {
+    it('should fail without a code', function() {
+      var call = new grpc.Call(channel, 'method', getDeadline(1));
+      assert.throws(function() {
+        var batch = {};
+        batch[grpc.opType.SEND_STATUS_FROM_SERVER] = {
+          details: 'details string',
+          metadata: {}
+        };
+        call.startBatch(batch, function(){});
+      }, TypeError);
+    });
+    it('should fail without details', function() {
+      var call = new grpc.Call(channel, 'method', getDeadline(1));
+      assert.throws(function() {
+        var batch = {};
+        batch[grpc.opType.SEND_STATUS_FROM_SERVER] = {
+          code: 0,
+          metadata: {}
+        };
+        call.startBatch(batch, function(){});
+      }, TypeError);
+    });
+    it('should fail without metadata', function() {
+      var call = new grpc.Call(channel, 'method', getDeadline(1));
+      assert.throws(function() {
+        var batch = {};
+        batch[grpc.opType.SEND_STATUS_FROM_SERVER] = {
+          code: 0,
+          details: 'details string'
+        };
+        call.startBatch(batch, function(){});
+      }, TypeError);
+    });
+    it('should fail with incorrectly typed code argument', function() {
+      var call = new grpc.Call(channel, 'method', getDeadline(1));
+      assert.throws(function() {
+        var batch = {};
+        batch[grpc.opType.SEND_STATUS_FROM_SERVER] = {
+          code: 'code string',
+          details: 'details string',
+          metadata: {}
+        };
+        call.startBatch(batch, function(){});
+      }, TypeError);
+    });
+    it('should fail with incorrectly typed details argument', function() {
+      var call = new grpc.Call(channel, 'method', getDeadline(1));
+      assert.throws(function() {
+        var batch = {};
+        batch[grpc.opType.SEND_STATUS_FROM_SERVER] = {
+          code: 0,
+          details: 5,
+          metadata: {}
+        };
+        call.startBatch(batch, function(){});
+      }, TypeError);
+    });
+    it('should fail with incorrectly typed metadata argument', function() {
+      var call = new grpc.Call(channel, 'method', getDeadline(1));
+      assert.throws(function() {
+        var batch = {};
+        batch[grpc.opType.SEND_STATUS_FROM_SERVER] = {
+          code: 0,
+          details: 'details string',
+          metadata: 'abc'
+        };
+        call.startBatch(batch, function(){});
+      }, TypeError);
+    });
+  });
   describe('cancel', function() {
     it('should succeed', function() {
       var call = new grpc.Call(channel, 'method', getDeadline(1));
diff --git a/src/objective-c/README.md b/src/objective-c/README.md
index 3624475..e76ee17 100644
--- a/src/objective-c/README.md
+++ b/src/objective-c/README.md
@@ -112,7 +112,7 @@
 ```ruby
   s.prepare_command = <<-CMD
     ...
-        #{src}/*.proto #{src}/**/*.proto
+        `find . -name *.proto -print | xargs`
   CMD
   ...
     ms.source_files = "#{dir}/*.pbobjc.{h,m}", "#{dir}/**/*.pbobjc.{h,m}"
diff --git a/src/php/ext/grpc/call.c b/src/php/ext/grpc/call.c
index 2f67e5c..c4997f7 100644
--- a/src/php/ext/grpc/call.c
+++ b/src/php/ext/grpc/call.c
@@ -214,10 +214,12 @@
     return;
   }
   wrapped_grpc_channel *channel = Z_WRAPPED_GRPC_CHANNEL_P(channel_obj);
-  if (channel->wrapped == NULL) {
+  gpr_mu_lock(&channel->wrapper->mu);
+  if (channel->wrapper->wrapped == NULL) {
     zend_throw_exception(spl_ce_InvalidArgumentException,
                          "Call cannot be constructed from a closed Channel",
                          1 TSRMLS_CC);
+    gpr_mu_unlock(&channel->wrapper->mu);
     return;
   }
   add_property_zval(getThis(), "channel", channel_obj);
@@ -226,13 +228,15 @@
   grpc_slice host_slice = host_override != NULL ?
       grpc_slice_from_copied_string(host_override) : grpc_empty_slice();
   call->wrapped =
-    grpc_channel_create_call(channel->wrapped, NULL, GRPC_PROPAGATE_DEFAULTS,
+    grpc_channel_create_call(channel->wrapper->wrapped, NULL,
+                             GRPC_PROPAGATE_DEFAULTS,
                              completion_queue, method_slice,
                              host_override != NULL ? &host_slice : NULL,
                              deadline->wrapped, NULL);
   grpc_slice_unref(method_slice);
   grpc_slice_unref(host_slice);
   call->owned = true;
+  gpr_mu_unlock(&channel->wrapper->mu);
 }
 
 /**
diff --git a/src/php/ext/grpc/call_credentials.c b/src/php/ext/grpc/call_credentials.c
index a990206..f46091d 100644
--- a/src/php/ext/grpc/call_credentials.c
+++ b/src/php/ext/grpc/call_credentials.c
@@ -109,8 +109,8 @@
   zend_fcall_info *fci;
   zend_fcall_info_cache *fci_cache;
 
-  fci = (zend_fcall_info *)emalloc(sizeof(zend_fcall_info));
-  fci_cache = (zend_fcall_info_cache *)emalloc(sizeof(zend_fcall_info_cache));
+  fci = (zend_fcall_info *)malloc(sizeof(zend_fcall_info));
+  fci_cache = (zend_fcall_info_cache *)malloc(sizeof(zend_fcall_info_cache));
   memset(fci, 0, sizeof(zend_fcall_info));
   memset(fci_cache, 0, sizeof(zend_fcall_info_cache));
 
@@ -123,7 +123,7 @@
   }
 
   plugin_state *state;
-  state = (plugin_state *)emalloc(sizeof(plugin_state));
+  state = (plugin_state *)malloc(sizeof(plugin_state));
   memset(state, 0, sizeof(plugin_state));
 
   /* save the user provided PHP callback function */
@@ -210,13 +210,13 @@
 /* Cleanup function for plugin creds API */
 void plugin_destroy_state(void *ptr) {
   plugin_state *state = (plugin_state *)ptr;
-  efree(state->fci);
-  efree(state->fci_cache);
+  free(state->fci);
+  free(state->fci_cache);
 #if PHP_MAJOR_VERSION < 7
   PHP_GRPC_FREE_STD_ZVAL(state->fci->params);
   PHP_GRPC_FREE_STD_ZVAL(state->fci->retval);
 #endif
-  efree(state);
+  free(state);
 }
 
 ZEND_BEGIN_ARG_INFO_EX(arginfo_createComposite, 0, 0, 2)
diff --git a/src/php/ext/grpc/channel.c b/src/php/ext/grpc/channel.c
index 6c432d2..f1187e8 100644
--- a/src/php/ext/grpc/channel.c
+++ b/src/php/ext/grpc/channel.c
@@ -25,6 +25,13 @@
 #include <php.h>
 #include <php_ini.h>
 #include <ext/standard/info.h>
+#include <ext/standard/php_var.h>
+#include <ext/standard/sha1.h>
+#if PHP_MAJOR_VERSION < 7
+#include <ext/standard/php_smart_str.h>
+#else
+#include <zend_smart_str.h>
+#endif
 #include <ext/spl/spl_exceptions.h>
 #include "php_grpc.h"
 
@@ -44,11 +51,25 @@
 #if PHP_MAJOR_VERSION >= 7
 static zend_object_handlers channel_ce_handlers;
 #endif
+static gpr_mu global_persistent_list_mu;
+int le_plink;
 
 /* Frees and destroys an instance of wrapped_grpc_channel */
 PHP_GRPC_FREE_WRAPPED_FUNC_START(wrapped_grpc_channel)
-  if (p->wrapped != NULL) {
-    grpc_channel_destroy(p->wrapped);
+  if (p->wrapper != NULL) {
+    gpr_mu_lock(&p->wrapper->mu);
+    if (p->wrapper->wrapped != NULL) {
+      php_grpc_zend_resource *rsrc;
+      php_grpc_int key_len = strlen(p->wrapper->key);
+      // only destroy the channel here if not found in the persistent list
+      gpr_mu_lock(&global_persistent_list_mu);
+      if (!(PHP_GRPC_PERSISTENT_LIST_FIND(&EG(persistent_list), p->wrapper->key,
+                                          key_len, rsrc))) {
+        grpc_channel_destroy(p->wrapper->wrapped);
+      }
+      gpr_mu_unlock(&global_persistent_list_mu);
+    }
+    gpr_mu_unlock(&p->wrapper->mu);
   }
 PHP_GRPC_FREE_WRAPPED_FUNC_END()
 
@@ -62,15 +83,15 @@
   PHP_GRPC_FREE_CLASS_OBJECT(wrapped_grpc_channel, channel_ce_handlers);
 }
 
-void php_grpc_read_args_array(zval *args_array,
-                              grpc_channel_args *args TSRMLS_DC) {
+int php_grpc_read_args_array(zval *args_array,
+                             grpc_channel_args *args TSRMLS_DC) {
   HashTable *array_hash;
   int args_index;
   array_hash = Z_ARRVAL_P(args_array);
   if (!array_hash) {
     zend_throw_exception(spl_ce_InvalidArgumentException,
                          "array_hash is NULL", 1 TSRMLS_CC);
-    return;
+    return FAILURE;
   }
   args->num_args = zend_hash_num_elements(array_hash);
   args->args = ecalloc(args->num_args, sizeof(grpc_arg));
@@ -84,7 +105,7 @@
     if (key_type != HASH_KEY_IS_STRING) {
       zend_throw_exception(spl_ce_InvalidArgumentException,
                            "args keys must be strings", 1 TSRMLS_CC);
-      return;
+      return FAILURE;
     }
     args->args[args_index].key = key;
     switch (Z_TYPE_P(data)) {
@@ -99,16 +120,78 @@
     default:
       zend_throw_exception(spl_ce_InvalidArgumentException,
                            "args values must be int or string", 1 TSRMLS_CC);
-      return;
+      return FAILURE;
     }
     args_index++;
   PHP_GRPC_HASH_FOREACH_END()
+  return SUCCESS;
+}
+
+void generate_sha1_str(char *sha1str, char *str, php_grpc_int len) {
+  PHP_SHA1_CTX context;
+  unsigned char digest[20];
+  sha1str[0] = '\0';
+  PHP_SHA1Init(&context);
+  PHP_GRPC_SHA1Update(&context, str, len);
+  PHP_SHA1Final(digest, &context);
+  make_sha1_digest(sha1str, digest);
+}
+
+void create_channel(
+    wrapped_grpc_channel *channel,
+    char *target,
+    grpc_channel_args args,
+    wrapped_grpc_channel_credentials *creds) {
+  if (creds == NULL) {
+    channel->wrapper->wrapped = grpc_insecure_channel_create(target, &args,
+                                                             NULL);
+  } else {
+    channel->wrapper->wrapped =
+        grpc_secure_channel_create(creds->wrapped, target, &args, NULL);
+  }
+  efree(args.args);
+}
+
+void create_and_add_channel_to_persistent_list(
+    wrapped_grpc_channel *channel,
+    char *target,
+    grpc_channel_args args,
+    wrapped_grpc_channel_credentials *creds,
+    char *key,
+    php_grpc_int key_len) {
+  php_grpc_zend_resource new_rsrc;
+  channel_persistent_le_t *le;
+  // this links each persistent list entry to a destructor
+  new_rsrc.type = le_plink;
+  le = malloc(sizeof(channel_persistent_le_t));
+
+  create_channel(channel, target, args, creds);
+
+  le->channel = channel->wrapper;
+  new_rsrc.ptr = le;
+  gpr_mu_lock(&global_persistent_list_mu);
+  PHP_GRPC_PERSISTENT_LIST_UPDATE(&EG(persistent_list), key, key_len,
+                                  (void *)&new_rsrc);
+  gpr_mu_unlock(&global_persistent_list_mu);
 }
 
 /**
- * Construct an instance of the Channel class. If the $args array contains a
- * "credentials" key mapping to a ChannelCredentials object, a secure channel
- * will be created with those credentials.
+ * Construct an instance of the Channel class.
+ *
+ * By default, the underlying grpc_channel is "persistent". That is, given
+ * the same set of parameters passed to the constructor, the same underlying
+ * grpc_channel will be returned.
+ *
+ * If the $args array contains a "credentials" key mapping to a
+ * ChannelCredentials object, a secure channel will be created with those
+ * credentials.
+ *
+ * If the $args array contains a "force_new" key mapping to a boolean value
+ * of "true", a new underlying grpc_channel will be created regardless. If
+ * there are any opened channels on the same hostname, user must manually
+ * call close() on those dangling channels before the end of the PHP
+ * script.
+ *
  * @param string $target The hostname to associate with this channel
  * @param array $args_array The arguments to pass to the Channel
  */
@@ -121,6 +204,9 @@
   grpc_channel_args args;
   HashTable *array_hash;
   wrapped_grpc_channel_credentials *creds = NULL;
+  php_grpc_zend_resource *rsrc;
+  bool force_new = false;
+  zval *force_new_obj = NULL;
 
   /* "sa" == 1 string, 1 array */
   if (zend_parse_parameters(ZEND_NUM_ARGS() TSRMLS_CC, "sa", &target,
@@ -131,7 +217,7 @@
   }
   array_hash = Z_ARRVAL_P(args_array);
   if (php_grpc_zend_hash_find(array_hash, "credentials", sizeof("credentials"),
-                     (void **)&creds_obj) == SUCCESS) {
+                              (void **)&creds_obj) == SUCCESS) {
     if (Z_TYPE_P(creds_obj) == IS_NULL) {
       creds = NULL;
       php_grpc_zend_hash_del(array_hash, "credentials", sizeof("credentials"));
@@ -146,14 +232,82 @@
       php_grpc_zend_hash_del(array_hash, "credentials", sizeof("credentials"));
     }
   }
-  php_grpc_read_args_array(args_array, &args TSRMLS_CC);
-  if (creds == NULL) {
-    channel->wrapped = grpc_insecure_channel_create(target, &args, NULL);
-  } else {
-    channel->wrapped =
-        grpc_secure_channel_create(creds->wrapped, target, &args, NULL);
+  if (php_grpc_zend_hash_find(array_hash, "force_new", sizeof("force_new"),
+                              (void **)&force_new_obj) == SUCCESS) {
+    if (PHP_GRPC_BVAL_IS_TRUE(force_new_obj)) {
+      force_new = true;
+    }
+    php_grpc_zend_hash_del(array_hash, "force_new", sizeof("force_new"));
   }
-  efree(args.args);
+
+  // parse the rest of the channel args array
+  if (php_grpc_read_args_array(args_array, &args TSRMLS_CC) == FAILURE) {
+    return;
+  }
+
+  // Construct a hashkey for the persistent channel
+  // Currently, the hashkey contains 3 parts:
+  // 1. hostname
+  // 2. hash value of the channel args array (excluding "credentials"
+  //    and "force_new")
+  // 3. (optional) hash value of the ChannelCredentials object
+  php_serialize_data_t var_hash;
+  smart_str buf = {0};
+  PHP_VAR_SERIALIZE_INIT(var_hash);
+  PHP_GRPC_VAR_SERIALIZE(&buf, args_array, &var_hash);
+  PHP_VAR_SERIALIZE_DESTROY(var_hash);
+
+  char sha1str[41];
+  generate_sha1_str(sha1str, PHP_GRPC_SERIALIZED_BUF_STR(buf),
+                    PHP_GRPC_SERIALIZED_BUF_LEN(buf));
+
+  php_grpc_int key_len = target_length + strlen(sha1str);
+  if (creds != NULL && creds->hashstr != NULL) {
+    key_len += strlen(creds->hashstr);
+  }
+  char *key = malloc(key_len + 1);
+  strcpy(key, target);
+  strcat(key, sha1str);
+  if (creds != NULL && creds->hashstr != NULL) {
+    strcat(key, creds->hashstr);
+  }
+  channel->wrapper = malloc(sizeof(grpc_channel_wrapper));
+  channel->wrapper->key = key;
+  channel->wrapper->target = target;
+  channel->wrapper->args_hashstr = sha1str;
+  if (creds != NULL && creds->hashstr != NULL) {
+    channel->wrapper->creds_hashstr = creds->hashstr;
+  }
+  gpr_mu_init(&channel->wrapper->mu);
+  smart_str_free(&buf);
+
+  if (force_new) {
+    php_grpc_delete_persistent_list_entry(key, key_len TSRMLS_CC);
+  }
+
+  if (creds != NULL && creds->has_call_creds) {
+    // If the ChannelCredentials object was composed with a CallCredentials
+    // object, there is no way we can tell them apart. Do NOT persist
+    // them. They should be individually destroyed.
+    create_channel(channel, target, args, creds);
+  } else if (!(PHP_GRPC_PERSISTENT_LIST_FIND(&EG(persistent_list), key,
+                                             key_len, rsrc))) {
+    create_and_add_channel_to_persistent_list(
+        channel, target, args, creds, key, key_len);
+  } else {
+    // Found a previously stored channel in the persistent list
+    channel_persistent_le_t *le = (channel_persistent_le_t *)rsrc->ptr;
+    if (strcmp(target, le->channel->target) != 0 ||
+        strcmp(sha1str, le->channel->args_hashstr) != 0 ||
+        (creds != NULL && creds->hashstr != NULL &&
+         strcmp(creds->hashstr, le->channel->creds_hashstr) != 0)) {
+      // somehow hash collision
+      create_and_add_channel_to_persistent_list(
+          channel, target, args, creds, key, key_len);
+    } else {
+      channel->wrapper = le->channel;
+    }
+  }
 }
 
 /**
@@ -162,7 +316,16 @@
  */
 PHP_METHOD(Channel, getTarget) {
   wrapped_grpc_channel *channel = Z_WRAPPED_GRPC_CHANNEL_P(getThis());
-  PHP_GRPC_RETURN_STRING(grpc_channel_get_target(channel->wrapped), 1);
+  gpr_mu_lock(&channel->wrapper->mu);
+  if (channel->wrapper->wrapped == NULL) {
+    zend_throw_exception(spl_ce_RuntimeException,
+                         "Channel already closed", 1 TSRMLS_CC);
+    gpr_mu_unlock(&channel->wrapper->mu);
+    return;
+  }
+  char *target = grpc_channel_get_target(channel->wrapper->wrapped);
+  gpr_mu_unlock(&channel->wrapper->mu);
+  PHP_GRPC_RETURN_STRING(target, 1);
 }
 
 /**
@@ -172,6 +335,14 @@
  */
 PHP_METHOD(Channel, getConnectivityState) {
   wrapped_grpc_channel *channel = Z_WRAPPED_GRPC_CHANNEL_P(getThis());
+  gpr_mu_lock(&channel->wrapper->mu);
+  if (channel->wrapper->wrapped == NULL) {
+    zend_throw_exception(spl_ce_RuntimeException,
+                         "Channel already closed", 1 TSRMLS_CC);
+    gpr_mu_unlock(&channel->wrapper->mu);
+    return;
+  }
+
   bool try_to_connect = false;
 
   /* "|b" == 1 optional bool */
@@ -179,10 +350,18 @@
       == FAILURE) {
     zend_throw_exception(spl_ce_InvalidArgumentException,
                          "getConnectivityState expects a bool", 1 TSRMLS_CC);
+    gpr_mu_unlock(&channel->wrapper->mu);
     return;
   }
-  RETURN_LONG(grpc_channel_check_connectivity_state(channel->wrapped,
-                                                    (int)try_to_connect));
+  int state = grpc_channel_check_connectivity_state(channel->wrapper->wrapped,
+                                                    (int)try_to_connect);
+  // this can happen if another shared Channel object close the underlying
+  // channel
+  if (state == GRPC_CHANNEL_SHUTDOWN) {
+    channel->wrapper->wrapped = NULL;
+  }
+  gpr_mu_unlock(&channel->wrapper->mu);
+  RETURN_LONG(state);
 }
 
 /**
@@ -194,25 +373,37 @@
  */
 PHP_METHOD(Channel, watchConnectivityState) {
   wrapped_grpc_channel *channel = Z_WRAPPED_GRPC_CHANNEL_P(getThis());
+  gpr_mu_lock(&channel->wrapper->mu);
+  if (channel->wrapper->wrapped == NULL) {
+    zend_throw_exception(spl_ce_RuntimeException,
+                         "Channel already closed", 1 TSRMLS_CC);
+    gpr_mu_unlock(&channel->wrapper->mu);
+    return;
+  }
+
   php_grpc_long last_state;
   zval *deadline_obj;
 
   /* "lO" == 1 long 1 object */
   if (zend_parse_parameters(ZEND_NUM_ARGS() TSRMLS_CC, "lO",
-          &last_state, &deadline_obj, grpc_ce_timeval) == FAILURE) {
+                            &last_state, &deadline_obj,
+                            grpc_ce_timeval) == FAILURE) {
     zend_throw_exception(spl_ce_InvalidArgumentException,
-        "watchConnectivityState expects 1 long 1 timeval", 1 TSRMLS_CC);
+                         "watchConnectivityState expects 1 long 1 timeval",
+                         1 TSRMLS_CC);
+    gpr_mu_unlock(&channel->wrapper->mu);
     return;
   }
 
   wrapped_grpc_timeval *deadline = Z_WRAPPED_GRPC_TIMEVAL_P(deadline_obj);
-  grpc_channel_watch_connectivity_state(channel->wrapped,
+  grpc_channel_watch_connectivity_state(channel->wrapper->wrapped,
                                         (grpc_connectivity_state)last_state,
                                         deadline->wrapped, completion_queue,
                                         NULL);
   grpc_event event =
-    grpc_completion_queue_pluck(completion_queue, NULL,
-                                gpr_inf_future(GPR_CLOCK_REALTIME), NULL);
+      grpc_completion_queue_pluck(completion_queue, NULL,
+                                  gpr_inf_future(GPR_CLOCK_REALTIME), NULL);
+  gpr_mu_unlock(&channel->wrapper->mu);
   RETURN_BOOL(event.success);
 }
 
@@ -222,10 +413,48 @@
  */
 PHP_METHOD(Channel, close) {
   wrapped_grpc_channel *channel = Z_WRAPPED_GRPC_CHANNEL_P(getThis());
-  if (channel->wrapped != NULL) {
-    grpc_channel_destroy(channel->wrapped);
-    channel->wrapped = NULL;
+  gpr_mu_lock(&channel->wrapper->mu);
+  if (channel->wrapper->wrapped != NULL) {
+    grpc_channel_destroy(channel->wrapper->wrapped);
+    channel->wrapper->wrapped = NULL;
   }
+
+  php_grpc_delete_persistent_list_entry(channel->wrapper->key,
+                                        strlen(channel->wrapper->key)
+                                        TSRMLS_CC);
+  gpr_mu_unlock(&channel->wrapper->mu);
+}
+
+// Delete an entry from the persistent list
+// Note: this does not destroy or close the underlying grpc_channel
+void php_grpc_delete_persistent_list_entry(char *key, php_grpc_int key_len
+                                           TSRMLS_DC) {
+  php_grpc_zend_resource *rsrc;
+  gpr_mu_lock(&global_persistent_list_mu);
+  if (PHP_GRPC_PERSISTENT_LIST_FIND(&EG(persistent_list), key,
+                                    key_len, rsrc)) {
+    channel_persistent_le_t *le;
+    le = (channel_persistent_le_t *)rsrc->ptr;
+    le->channel = NULL;
+    php_grpc_zend_hash_del(&EG(persistent_list), key, key_len+1);
+  }
+  gpr_mu_unlock(&global_persistent_list_mu);
+}
+
+// A destructor associated with each list entry from the persistent list
+static void php_grpc_channel_plink_dtor(php_grpc_zend_resource *rsrc
+                                        TSRMLS_DC) {
+  channel_persistent_le_t *le = (channel_persistent_le_t *)rsrc->ptr;
+  if (le->channel != NULL) {
+    gpr_mu_lock(&le->channel->mu);
+    if (le->channel->wrapped != NULL) {
+      grpc_channel_destroy(le->channel->wrapped);
+      free(le->channel->key);
+      free(le->channel);
+    }
+    gpr_mu_unlock(&le->channel->mu);
+  }
+  free(le);
 }
 
 ZEND_BEGIN_ARG_INFO_EX(arginfo_construct, 0, 0, 2)
@@ -262,10 +491,13 @@
   PHP_FE_END
 };
 
-void grpc_init_channel(TSRMLS_D) {
+GRPC_STARTUP_FUNCTION(channel) {
   zend_class_entry ce;
   INIT_CLASS_ENTRY(ce, "Grpc\\Channel", channel_methods);
   ce.create_object = create_wrapped_grpc_channel;
   grpc_ce_channel = zend_register_internal_class(&ce TSRMLS_CC);
+  le_plink = zend_register_list_destructors_ex(
+      NULL, php_grpc_channel_plink_dtor, "Persistent Channel", module_number);
   PHP_GRPC_INIT_HANDLER(wrapped_grpc_channel, channel_ce_handlers);
+  return SUCCESS;
 }
diff --git a/src/php/ext/grpc/channel.h b/src/php/ext/grpc/channel.h
index 45c9744..69adc47 100755
--- a/src/php/ext/grpc/channel.h
+++ b/src/php/ext/grpc/channel.h
@@ -33,9 +33,18 @@
 /* Class entry for the PHP Channel class */
 extern zend_class_entry *grpc_ce_channel;
 
+typedef struct _grpc_channel_wrapper {
+  grpc_channel *wrapped;
+  char *key;
+  char *target;
+  char *args_hashstr;
+  char *creds_hashstr;
+  gpr_mu mu;
+} grpc_channel_wrapper;
+
 /* Wrapper struct for grpc_channel that can be associated with a PHP object */
 PHP_GRPC_WRAP_OBJECT_START(wrapped_grpc_channel)
-  grpc_channel *wrapped;
+  grpc_channel_wrapper *wrapper;
 PHP_GRPC_WRAP_OBJECT_END(wrapped_grpc_channel)
 
 #if PHP_MAJOR_VERSION < 7
@@ -57,10 +66,20 @@
 #endif /* PHP_MAJOR_VERSION */
 
 /* Initializes the Channel class */
-void grpc_init_channel(TSRMLS_D);
+GRPC_STARTUP_FUNCTION(channel);
 
 /* Iterates through a PHP array and populates args with the contents */
-void php_grpc_read_args_array(zval *args_array, grpc_channel_args *args
-                              TSRMLS_DC);
+int php_grpc_read_args_array(zval *args_array, grpc_channel_args *args
+                             TSRMLS_DC);
+
+void generate_sha1_str(char *sha1str, char *str, php_grpc_int len);
+
+void php_grpc_delete_persistent_list_entry(char *key, php_grpc_int key_len
+                                           TSRMLS_DC);
+
+typedef struct _channel_persistent_le {
+  grpc_channel_wrapper *channel;
+} channel_persistent_le_t;
+
 
 #endif /* NET_GRPC_PHP_GRPC_CHANNEL_H_ */
diff --git a/src/php/ext/grpc/channel_credentials.c b/src/php/ext/grpc/channel_credentials.c
index 40629c8..19e1cef 100644
--- a/src/php/ext/grpc/channel_credentials.c
+++ b/src/php/ext/grpc/channel_credentials.c
@@ -26,7 +26,9 @@
 #include <php.h>
 #include <php_ini.h>
 #include <ext/standard/info.h>
+#include <ext/standard/sha1.h>
 #include <ext/spl/spl_exceptions.h>
+#include "channel.h"
 #include "php_grpc.h"
 
 #include <zend_exceptions.h>
@@ -69,14 +71,17 @@
                              channel_credentials_ce_handlers);
 }
 
-zval *grpc_php_wrap_channel_credentials(grpc_channel_credentials
-                                        *wrapped TSRMLS_DC) {
+zval *grpc_php_wrap_channel_credentials(grpc_channel_credentials *wrapped,
+                                        char *hashstr,
+                                        zend_bool has_call_creds TSRMLS_DC) {
   zval *credentials_object;
   PHP_GRPC_MAKE_STD_ZVAL(credentials_object);
   object_init_ex(credentials_object, grpc_ce_channel_credentials);
   wrapped_grpc_channel_credentials *credentials =
     Z_WRAPPED_GRPC_CHANNEL_CREDS_P(credentials_object);
   credentials->wrapped = wrapped;
+  credentials->hashstr = hashstr;
+  credentials->has_call_creds = has_call_creds;
   return credentials_object;
 }
 
@@ -106,7 +111,8 @@
  */
 PHP_METHOD(ChannelCredentials, createDefault) {
   grpc_channel_credentials *creds = grpc_google_default_credentials_create();
-  zval *creds_object = grpc_php_wrap_channel_credentials(creds TSRMLS_CC);
+  zval *creds_object = grpc_php_wrap_channel_credentials(creds, NULL, false
+                                                         TSRMLS_CC);
   RETURN_DESTROY_ZVAL(creds_object);
 }
 
@@ -140,10 +146,24 @@
                          "createSsl expects 3 optional strings", 1 TSRMLS_CC);
     return;
   }
+
+  php_grpc_int hashkey_len = root_certs_length + cert_chain_length;
+  char hashkey[hashkey_len];
+  if (root_certs_length > 0) {
+    strcpy(hashkey, pem_root_certs);
+  }
+  if (cert_chain_length > 0) {
+    strcpy(hashkey, pem_key_cert_pair.cert_chain);
+  }
+
+  char *hashstr = malloc(41);
+  generate_sha1_str(hashstr, hashkey, hashkey_len);
+
   grpc_channel_credentials *creds = grpc_ssl_credentials_create(
       pem_root_certs,
       pem_key_cert_pair.private_key == NULL ? NULL : &pem_key_cert_pair, NULL);
-  zval *creds_object = grpc_php_wrap_channel_credentials(creds TSRMLS_CC);
+  zval *creds_object = grpc_php_wrap_channel_credentials(creds, hashstr, false
+                                                         TSRMLS_CC);
   RETURN_DESTROY_ZVAL(creds_object);
 }
 
@@ -172,7 +192,9 @@
   grpc_channel_credentials *creds =
       grpc_composite_channel_credentials_create(cred1->wrapped, cred2->wrapped,
                                                 NULL);
-  zval *creds_object = grpc_php_wrap_channel_credentials(creds TSRMLS_CC);
+  zval *creds_object =
+      grpc_php_wrap_channel_credentials(creds, cred1->hashstr, true
+                                        TSRMLS_CC);
   RETURN_DESTROY_ZVAL(creds_object);
 }
 
diff --git a/src/php/ext/grpc/channel_credentials.h b/src/php/ext/grpc/channel_credentials.h
index 28c7f2c..357d732 100755
--- a/src/php/ext/grpc/channel_credentials.h
+++ b/src/php/ext/grpc/channel_credentials.h
@@ -38,6 +38,8 @@
  * with a PHP object */
 PHP_GRPC_WRAP_OBJECT_START(wrapped_grpc_channel_credentials) 
   grpc_channel_credentials *wrapped;
+  char *hashstr;
+  zend_bool has_call_creds;
 PHP_GRPC_WRAP_OBJECT_END(wrapped_grpc_channel_credentials)
 
 #if PHP_MAJOR_VERSION < 7
diff --git a/src/php/ext/grpc/php7_wrapper.h b/src/php/ext/grpc/php7_wrapper.h
index d4b4c26..96091f9 100644
--- a/src/php/ext/grpc/php7_wrapper.h
+++ b/src/php/ext/grpc/php7_wrapper.h
@@ -113,6 +113,20 @@
 }
 
 #define php_grpc_zend_hash_del zend_hash_del
+#define php_grpc_zend_resource zend_rsrc_list_entry
+
+#define PHP_GRPC_BVAL_IS_TRUE(zv) Z_LVAL_P(zv)
+#define PHP_GRPC_VAR_SERIALIZE(buf, zv, hash) \
+  php_var_serialize(buf, &zv, hash TSRMLS_CC)
+#define PHP_GRPC_SERIALIZED_BUF_STR(buf) buf.c
+#define PHP_GRPC_SERIALIZED_BUF_LEN(buf) buf.len
+#define PHP_GRPC_SHA1Update(cxt, str, len)     \
+  PHP_SHA1Update(cxt, (const unsigned char *)str, len)
+#define PHP_GRPC_PERSISTENT_LIST_FIND(plist, key, len, rsrc) \
+  zend_hash_find(plist, key, len+1, (void **)&rsrc) != FAILURE
+#define PHP_GRPC_PERSISTENT_LIST_UPDATE(plist, key, len, rsrc) \
+  zend_hash_update(plist, key, len+1, rsrc, sizeof(php_grpc_zend_resource), \
+                   NULL)
 
 #define PHP_GRPC_GET_CLASS_ENTRY(object) zend_get_class_entry(object TSRMLS_CC)
 
@@ -200,6 +214,20 @@
 static inline int php_grpc_zend_hash_del(HashTable *ht, char *key, int len) {
   return zend_hash_str_del(ht, key, len - 1);
 }
+#define php_grpc_zend_resource zend_resource
+
+#define PHP_GRPC_BVAL_IS_TRUE(zv) Z_TYPE_P(zv) == IS_TRUE
+#define PHP_GRPC_VAR_SERIALIZE(buf, zv, hash)   \
+  php_var_serialize(buf, zv, hash)
+#define PHP_GRPC_SERIALIZED_BUF_STR(buf) ZSTR_VAL(buf.s)
+#define PHP_GRPC_SERIALIZED_BUF_LEN(buf) ZSTR_LEN(buf.s)
+#define PHP_GRPC_SHA1Update(cxt, str, len)      \
+  PHP_SHA1Update(cxt, (unsigned char *)str, len)
+#define PHP_GRPC_PERSISTENT_LIST_FIND(plist, key, len, rsrc) \
+  (rsrc = zend_hash_str_find_ptr(plist, key, len)) != NULL
+#define PHP_GRPC_PERSISTENT_LIST_UPDATE(plist, key, len, rsrc) \
+  zend_hash_str_update_mem(plist, key, len, rsrc, \
+                           sizeof(php_grpc_zend_resource))
 
 #define PHP_GRPC_GET_CLASS_ENTRY(object) Z_OBJ_P(object)->ce
 
diff --git a/src/php/ext/grpc/php_grpc.c b/src/php/ext/grpc/php_grpc.c
index 281b9e6..a96daf7 100644
--- a/src/php/ext/grpc/php_grpc.c
+++ b/src/php/ext/grpc/php_grpc.c
@@ -221,7 +221,7 @@
                          CONST_CS | CONST_PERSISTENT);
 
   grpc_init_call(TSRMLS_C);
-  grpc_init_channel(TSRMLS_C);
+  GRPC_STARTUP(channel);
   grpc_init_server(TSRMLS_C);
   grpc_init_timeval(TSRMLS_C);
   grpc_init_channel_credentials(TSRMLS_C);
diff --git a/src/php/ext/grpc/php_grpc.h b/src/php/ext/grpc/php_grpc.h
index ed846fd..3232917 100644
--- a/src/php/ext/grpc/php_grpc.h
+++ b/src/php/ext/grpc/php_grpc.h
@@ -74,4 +74,8 @@
 #define GRPC_G(v) (grpc_globals.v)
 #endif
 
+#define GRPC_STARTUP_FUNCTION(module)  ZEND_MINIT_FUNCTION(grpc_##module)
+#define GRPC_STARTUP(module)           \
+  ZEND_MODULE_STARTUP_N(grpc_##module)(INIT_FUNC_ARGS_PASSTHRU)
+
 #endif /* PHP_GRPC_H */
diff --git a/src/php/tests/unit_tests/CallTest.php b/src/php/tests/unit_tests/CallTest.php
index 3270e73..c5e1890 100644
--- a/src/php/tests/unit_tests/CallTest.php
+++ b/src/php/tests/unit_tests/CallTest.php
@@ -37,8 +37,7 @@
 
     public function tearDown()
     {
-        unset($this->call);
-        unset($this->channel);
+        $this->channel->close();
     }
 
     public function testConstructor()
diff --git a/src/php/tests/unit_tests/ChannelTest.php b/src/php/tests/unit_tests/ChannelTest.php
index 34e6185..400df0f 100644
--- a/src/php/tests/unit_tests/ChannelTest.php
+++ b/src/php/tests/unit_tests/ChannelTest.php
@@ -25,17 +25,15 @@
 
     public function tearDown()
     {
-        unset($this->channel);
+        if (!empty($this->channel)) {
+            $this->channel->close();
+        }
     }
 
     public function testInsecureCredentials()
     {
-        $this->channel = new Grpc\Channel(
-            'localhost:0',
-            [
-                'credentials' => Grpc\ChannelCredentials::createInsecure(),
-            ]
-        );
+        $this->channel = new Grpc\Channel('localhost:0',
+            ['credentials' => Grpc\ChannelCredentials::createInsecure()]);
         $this->assertSame('Grpc\Channel', get_class($this->channel));
     }
 
@@ -111,7 +109,7 @@
      */
     public function testInvalidConstructorWith()
     {
-        $this->channel = new Grpc\Channel('localhost', 'invalid');
+        $this->channel = new Grpc\Channel('localhost:0', 'invalid');
         $this->assertNull($this->channel);
     }
 
@@ -120,12 +118,8 @@
      */
     public function testInvalidCredentials()
     {
-        $this->channel = new Grpc\Channel(
-            'localhost:0',
-            [
-                'credentials' => new Grpc\Timeval(100),
-            ]
-        );
+        $this->channel = new Grpc\Channel('localhost:0',
+            ['credentials' => new Grpc\Timeval(100)]);
     }
 
     /**
@@ -133,12 +127,8 @@
      */
     public function testInvalidOptionsArray()
     {
-        $this->channel = new Grpc\Channel(
-            'localhost:0',
-            [
-                'abc' => [],
-            ]
-        );
+        $this->channel = new Grpc\Channel('localhost:0',
+            ['abc' => []]);
     }
 
     /**
@@ -170,4 +160,431 @@
             ['credentials' => Grpc\ChannelCredentials::createInsecure()]);
         $this->channel->watchConnectivityState(1, 'hi');
     }
+
+
+    public function assertConnecting($state) {
+      $this->assertTrue($state == GRPC\CHANNEL_CONNECTING ||
+                        $state == GRPC\CHANNEL_TRANSIENT_FAILURE);
+    }
+
+    public function waitUntilNotIdle($channel) {
+        for ($i = 0; $i < 10; $i++) {
+            $now = Grpc\Timeval::now();
+            $deadline = $now->add(new Grpc\Timeval(1000));
+            if ($channel->watchConnectivityState(GRPC\CHANNEL_IDLE,
+                                                 $deadline)) {
+                return true;
+            }
+        }
+        $this->assertTrue(false);
+    }
+
+    public function testPersistentChannelSameHost()
+    {
+        $this->channel1 = new Grpc\Channel('localhost:1', []);
+        // the underlying grpc channel is the same by default
+        // when connecting to the same host
+        $this->channel2 = new Grpc\Channel('localhost:1', []);
+
+        // both channels should be IDLE
+        $state = $this->channel1->getConnectivityState();
+        $this->assertEquals(GRPC\CHANNEL_IDLE, $state);
+        $state = $this->channel2->getConnectivityState();
+        $this->assertEquals(GRPC\CHANNEL_IDLE, $state);
+
+        // try to connect on channel1
+        $state = $this->channel1->getConnectivityState(true);
+        $this->waitUntilNotIdle($this->channel1);
+
+        // both channels should now be in the CONNECTING state
+        $state = $this->channel1->getConnectivityState();
+        $this->assertConnecting($state);
+        $state = $this->channel2->getConnectivityState();
+        $this->assertConnecting($state);
+
+        $this->channel1->close();
+        $this->channel2->close();
+    }
+
+    public function testPersistentChannelDifferentHost()
+    {
+        // two different underlying channels because different hostname
+        $this->channel1 = new Grpc\Channel('localhost:1', []);
+        $this->channel2 = new Grpc\Channel('localhost:2', []);
+
+        // both channels should be IDLE
+        $state = $this->channel1->getConnectivityState();
+        $this->assertEquals(GRPC\CHANNEL_IDLE, $state);
+        $state = $this->channel2->getConnectivityState();
+        $this->assertEquals(GRPC\CHANNEL_IDLE, $state);
+
+        // try to connect on channel1
+        $state = $this->channel1->getConnectivityState(true);
+        $this->waitUntilNotIdle($this->channel1);
+
+        // channel1 should now be in the CONNECTING state
+        $state = $this->channel1->getConnectivityState();
+        $this->assertConnecting($state);
+        // channel2 should still be in the IDLE state
+        $state = $this->channel2->getConnectivityState();
+        $this->assertEquals(GRPC\CHANNEL_IDLE, $state);
+
+        $this->channel1->close();
+        $this->channel2->close();
+    }
+
+    public function testPersistentChannelSameArgs()
+    {
+        $this->channel1 = new Grpc\Channel('localhost:1', ["abc" => "def"]);
+        $this->channel2 = new Grpc\Channel('localhost:1', ["abc" => "def"]);
+
+        // try to connect on channel1
+        $state = $this->channel1->getConnectivityState(true);
+        $this->waitUntilNotIdle($this->channel1);
+
+        $state = $this->channel1->getConnectivityState();
+        $this->assertConnecting($state);
+        $state = $this->channel2->getConnectivityState();
+        $this->assertConnecting($state);
+
+        $this->channel1->close();
+        $this->channel2->close();
+    }
+
+    public function testPersistentChannelDifferentArgs()
+    {
+        $this->channel1 = new Grpc\Channel('localhost:1', []);
+        $this->channel2 = new Grpc\Channel('localhost:1', ["abc" => "def"]);
+
+        // try to connect on channel1
+        $state = $this->channel1->getConnectivityState(true);
+        $this->waitUntilNotIdle($this->channel1);
+
+        $state = $this->channel1->getConnectivityState();
+        $this->assertConnecting($state);
+        $state = $this->channel2->getConnectivityState();
+        $this->assertEquals(GRPC\CHANNEL_IDLE, $state);
+
+        $this->channel1->close();
+        $this->channel2->close();
+    }
+
+    public function testPersistentChannelSameChannelCredentials()
+    {
+        $creds1 = Grpc\ChannelCredentials::createSsl();
+        $creds2 = Grpc\ChannelCredentials::createSsl();
+
+        $this->channel1 = new Grpc\Channel('localhost:1',
+                                           ["credentials" => $creds1]);
+        $this->channel2 = new Grpc\Channel('localhost:1',
+                                           ["credentials" => $creds2]);
+
+        // try to connect on channel1
+        $state = $this->channel1->getConnectivityState(true);
+        $this->waitUntilNotIdle($this->channel1);
+
+        $state = $this->channel1->getConnectivityState();
+        $this->assertConnecting($state);
+        $state = $this->channel2->getConnectivityState();
+        $this->assertConnecting($state);
+
+        $this->channel1->close();
+        $this->channel2->close();
+    }
+
+    public function testPersistentChannelDifferentChannelCredentials()
+    {
+        $creds1 = Grpc\ChannelCredentials::createSsl();
+        $creds2 = Grpc\ChannelCredentials::createSsl(
+            file_get_contents(dirname(__FILE__).'/../data/ca.pem'));
+
+        $this->channel1 = new Grpc\Channel('localhost:1',
+                                           ["credentials" => $creds1]);
+        $this->channel2 = new Grpc\Channel('localhost:1',
+                                           ["credentials" => $creds2]);
+
+        // try to connect on channel1
+        $state = $this->channel1->getConnectivityState(true);
+        $this->waitUntilNotIdle($this->channel1);
+
+        $state = $this->channel1->getConnectivityState();
+        $this->assertConnecting($state);
+        $state = $this->channel2->getConnectivityState();
+        $this->assertEquals(GRPC\CHANNEL_IDLE, $state);
+
+        $this->channel1->close();
+        $this->channel2->close();
+    }
+
+    public function testPersistentChannelSameChannelCredentialsRootCerts()
+    {
+        $creds1 = Grpc\ChannelCredentials::createSsl(
+            file_get_contents(dirname(__FILE__).'/../data/ca.pem'));
+        $creds2 = Grpc\ChannelCredentials::createSsl(
+            file_get_contents(dirname(__FILE__).'/../data/ca.pem'));
+
+        $this->channel1 = new Grpc\Channel('localhost:1',
+                                           ["credentials" => $creds1]);
+        $this->channel2 = new Grpc\Channel('localhost:1',
+                                           ["credentials" => $creds2]);
+
+        // try to connect on channel1
+        $state = $this->channel1->getConnectivityState(true);
+        $this->waitUntilNotIdle($this->channel1);
+
+        $state = $this->channel1->getConnectivityState();
+        $this->assertConnecting($state);
+        $state = $this->channel2->getConnectivityState();
+        $this->assertConnecting($state);
+
+        $this->channel1->close();
+        $this->channel2->close();
+    }
+
+    public function testPersistentChannelDifferentSecureChannelCredentials()
+    {
+        $creds1 = Grpc\ChannelCredentials::createSsl();
+        $creds2 = Grpc\ChannelCredentials::createInsecure();
+
+        $this->channel1 = new Grpc\Channel('localhost:1',
+                                           ["credentials" => $creds1]);
+        $this->channel2 = new Grpc\Channel('localhost:1',
+                                           ["credentials" => $creds2]);
+
+        // try to connect on channel1
+        $state = $this->channel1->getConnectivityState(true);
+        $this->waitUntilNotIdle($this->channel1);
+
+        $state = $this->channel1->getConnectivityState();
+        $this->assertConnecting($state);
+        $state = $this->channel2->getConnectivityState();
+        $this->assertEquals(GRPC\CHANNEL_IDLE, $state);
+
+        $this->channel1->close();
+        $this->channel2->close();
+    }
+
+    /**
+     * @expectedException RuntimeException
+     */
+    public function testPersistentChannelSharedChannelClose()
+    {
+        // same underlying channel
+        $this->channel1 = new Grpc\Channel('localhost:1', []);
+        $this->channel2 = new Grpc\Channel('localhost:1', []);
+
+        // close channel1
+        $this->channel1->close();
+
+        // channel2 is now in SHUTDOWN state
+        $state = $this->channel2->getConnectivityState();
+        $this->assertEquals(GRPC\CHANNEL_FATAL_FAILURE, $state);
+
+        // calling it again will result in an exception because the
+        // channel is already closed
+        $state = $this->channel2->getConnectivityState();
+    }
+
+    public function testPersistentChannelCreateAfterClose()
+    {
+        $this->channel1 = new Grpc\Channel('localhost:1', []);
+
+        $this->channel1->close();
+
+        $this->channel2 = new Grpc\Channel('localhost:1', []);
+        $state = $this->channel2->getConnectivityState();
+        $this->assertEquals(GRPC\CHANNEL_IDLE, $state);
+
+        $this->channel2->close();
+    }
+
+    public function testPersistentChannelSharedMoreThanTwo()
+    {
+        $this->channel1 = new Grpc\Channel('localhost:1', []);
+        $this->channel2 = new Grpc\Channel('localhost:1', []);
+        $this->channel3 = new Grpc\Channel('localhost:1', []);
+
+        // try to connect on channel1
+        $state = $this->channel1->getConnectivityState(true);
+        $this->waitUntilNotIdle($this->channel1);
+
+        // all 3 channels should be in CONNECTING state
+        $state = $this->channel1->getConnectivityState();
+        $this->assertConnecting($state);
+        $state = $this->channel2->getConnectivityState();
+        $this->assertConnecting($state);
+        $state = $this->channel3->getConnectivityState();
+        $this->assertConnecting($state);
+
+        $this->channel1->close();
+    }
+
+    public function callbackFunc($context)
+    {
+        return [];
+    }
+
+    public function callbackFunc2($context)
+    {
+        return ["k1" => "v1"];
+    }
+
+    public function testPersistentChannelWithCallCredentials()
+    {
+        $creds = Grpc\ChannelCredentials::createSsl();
+        $callCreds = Grpc\CallCredentials::createFromPlugin(
+            [$this, 'callbackFunc']);
+        $credsWithCallCreds = Grpc\ChannelCredentials::createComposite(
+            $creds, $callCreds);
+
+        // If a ChannelCredentials object is composed with a
+        // CallCredentials object, the underlying grpc channel will
+        // always be created new and NOT persisted.
+        $this->channel1 = new Grpc\Channel('localhost:1',
+                                           ["credentials" =>
+                                            $credsWithCallCreds]);
+        $this->channel2 = new Grpc\Channel('localhost:1',
+                                           ["credentials" =>
+                                            $credsWithCallCreds]);
+
+        // try to connect on channel1
+        $state = $this->channel1->getConnectivityState(true);
+        $this->waitUntilNotIdle($this->channel1);
+
+        $state = $this->channel1->getConnectivityState();
+        $this->assertConnecting($state);
+        $state = $this->channel2->getConnectivityState();
+        $this->assertEquals(GRPC\CHANNEL_IDLE, $state);
+
+        $this->channel1->close();
+        $this->channel2->close();
+    }
+
+    public function testPersistentChannelWithDifferentCallCredentials()
+    {
+        $callCreds1 = Grpc\CallCredentials::createFromPlugin(
+            [$this, 'callbackFunc']);
+        $callCreds2 = Grpc\CallCredentials::createFromPlugin(
+            [$this, 'callbackFunc2']);
+
+        $creds1 = Grpc\ChannelCredentials::createSsl();
+        $creds2 = Grpc\ChannelCredentials::createComposite(
+            $creds1, $callCreds1);
+        $creds3 = Grpc\ChannelCredentials::createComposite(
+            $creds1, $callCreds2);
+
+        // Similar to the test above, anytime a ChannelCredentials
+        // object is composed with a CallCredentials object, the
+        // underlying grpc channel will always be separate and not
+        // persisted
+        $this->channel1 = new Grpc\Channel('localhost:1',
+                                           ["credentials" => $creds1]);
+        $this->channel2 = new Grpc\Channel('localhost:1',
+                                           ["credentials" => $creds2]);
+        $this->channel3 = new Grpc\Channel('localhost:1',
+                                           ["credentials" => $creds3]);
+
+        // try to connect on channel1
+        $state = $this->channel1->getConnectivityState(true);
+        $this->waitUntilNotIdle($this->channel1);
+
+        $state = $this->channel1->getConnectivityState();
+        $this->assertConnecting($state);
+        $state = $this->channel2->getConnectivityState();
+        $this->assertEquals(GRPC\CHANNEL_IDLE, $state);
+        $state = $this->channel3->getConnectivityState();
+        $this->assertEquals(GRPC\CHANNEL_IDLE, $state);
+
+        $this->channel1->close();
+        $this->channel2->close();
+        $this->channel3->close();
+    }
+
+    public function testPersistentChannelForceNew()
+    {
+        $this->channel1 = new Grpc\Channel('localhost:1', []);
+        // even though all the channel params are the same, channel2
+        // has a new and different underlying channel
+        $this->channel2 = new Grpc\Channel('localhost:1',
+                                           ["force_new" => true]);
+
+        // try to connect on channel1
+        $state = $this->channel1->getConnectivityState(true);
+        $this->waitUntilNotIdle($this->channel1);
+
+        $state = $this->channel1->getConnectivityState();
+        $this->assertConnecting($state);
+        $state = $this->channel2->getConnectivityState();
+        $this->assertEquals(GRPC\CHANNEL_IDLE, $state);
+
+        // any dangling old connection to the same host must be
+        // manually closed
+        $this->channel1->close();
+        $this->channel2->close();
+    }
+
+    public function testPersistentChannelForceNewOldChannelIdle()
+    {
+
+        $this->channel1 = new Grpc\Channel('localhost:1', []);
+        $this->channel2 = new Grpc\Channel('localhost:1',
+                                           ["force_new" => true]);
+        $this->channel3 = new Grpc\Channel('localhost:1', []);
+
+        // try to connect on channel2
+        $state = $this->channel2->getConnectivityState(true);
+        $this->waitUntilNotIdle($this->channel2);
+
+        $state = $this->channel1->getConnectivityState();
+        $this->assertEquals(GRPC\CHANNEL_IDLE, $state);
+        $state = $this->channel2->getConnectivityState();
+        $this->assertConnecting($state);
+        $state = $this->channel3->getConnectivityState();
+        $this->assertConnecting($state);
+
+        $this->channel1->close();
+        $this->channel2->close();
+    }
+
+    public function testPersistentChannelForceNewOldChannelClose()
+    {
+
+        $this->channel1 = new Grpc\Channel('localhost:1', []);
+        $this->channel2 = new Grpc\Channel('localhost:1',
+                                           ["force_new" => true]);
+        $this->channel3 = new Grpc\Channel('localhost:1', []);
+
+        $this->channel1->close();
+
+        $state = $this->channel2->getConnectivityState();
+        $this->assertEquals(GRPC\CHANNEL_IDLE, $state);
+        $state = $this->channel3->getConnectivityState();
+        $this->assertEquals(GRPC\CHANNEL_IDLE, $state);
+
+        $this->channel2->close();
+        $this->channel3->close();
+    }
+
+    public function testPersistentChannelForceNewNewChannelClose()
+    {
+
+        $this->channel1 = new Grpc\Channel('localhost:1', []);
+        $this->channel2 = new Grpc\Channel('localhost:1',
+                                           ["force_new" => true]);
+        $this->channel3 = new Grpc\Channel('localhost:1', []);
+
+        $this->channel2->close();
+
+        $state = $this->channel1->getConnectivityState();
+        $this->assertEquals(GRPC\CHANNEL_IDLE, $state);
+
+        // can still connect on channel1
+        $state = $this->channel1->getConnectivityState(true);
+        $this->waitUntilNotIdle($this->channel1);
+
+        $state = $this->channel1->getConnectivityState();
+        $this->assertConnecting($state);
+
+        $this->channel1->close();
+    }
 }
diff --git a/src/php/tests/unit_tests/EndToEndTest.php b/src/php/tests/unit_tests/EndToEndTest.php
index 43d54d9..b54f1d8 100644
--- a/src/php/tests/unit_tests/EndToEndTest.php
+++ b/src/php/tests/unit_tests/EndToEndTest.php
@@ -28,8 +28,7 @@
 
     public function tearDown()
     {
-        unset($this->channel);
-        unset($this->server);
+        $this->channel->close();
     }
 
     public function testSimpleRequestBody()
@@ -516,7 +515,7 @@
         $this->assertTrue($idle_state == Grpc\CHANNEL_IDLE);
 
         $now = Grpc\Timeval::now();
-        $delta = new Grpc\Timeval(500000); // should timeout
+        $delta = new Grpc\Timeval(50000); // should timeout
         $deadline = $now->add($delta);
 
         $this->assertFalse($this->channel->watchConnectivityState(
@@ -545,7 +544,7 @@
         $this->assertTrue($idle_state == Grpc\CHANNEL_IDLE);
 
         $now = Grpc\Timeval::now();
-        $delta = new Grpc\Timeval(100000);
+        $delta = new Grpc\Timeval(50000);
         $deadline = $now->add($delta);
 
         $this->assertFalse($this->channel->watchConnectivityState(
diff --git a/src/php/tests/unit_tests/SecureEndToEndTest.php b/src/php/tests/unit_tests/SecureEndToEndTest.php
index 0fecbfb..dff4e87 100644
--- a/src/php/tests/unit_tests/SecureEndToEndTest.php
+++ b/src/php/tests/unit_tests/SecureEndToEndTest.php
@@ -43,8 +43,7 @@
 
     public function tearDown()
     {
-        unset($this->channel);
-        unset($this->server);
+        $this->channel->close();
     }
 
     public function testSimpleRequestBody()
diff --git a/src/python/grpcio/grpc_core_dependencies.py b/src/python/grpcio/grpc_core_dependencies.py
index aa074df..dc4d28f 100644
--- a/src/python/grpcio/grpc_core_dependencies.py
+++ b/src/python/grpcio/grpc_core_dependencies.py
@@ -92,6 +92,9 @@
   'src/core/lib/iomgr/ev_windows.c',
   'src/core/lib/iomgr/exec_ctx.c',
   'src/core/lib/iomgr/executor.c',
+  'src/core/lib/iomgr/gethostname_fallback.c',
+  'src/core/lib/iomgr/gethostname_host_name_max.c',
+  'src/core/lib/iomgr/gethostname_sysconf.c',
   'src/core/lib/iomgr/iocp_windows.c',
   'src/core/lib/iomgr/iomgr.c',
   'src/core/lib/iomgr/iomgr_posix.c',
@@ -243,6 +246,7 @@
   'src/core/tsi/fake_transport_security.c',
   'src/core/tsi/gts_transport_security.c',
   'src/core/tsi/ssl_transport_security.c',
+  'src/core/tsi/transport_security_grpc.c',
   'src/core/tsi/transport_security.c',
   'src/core/tsi/transport_security_adapter.c',
   'src/core/ext/transport/chttp2/server/chttp2_server.c',
diff --git a/src/python/grpcio_testing/grpc_testing/__init__.py b/src/python/grpcio_testing/grpc_testing/__init__.py
index c5a17f4..14e25f0 100644
--- a/src/python/grpcio_testing/grpc_testing/__init__.py
+++ b/src/python/grpcio_testing/grpc_testing/__init__.py
@@ -15,11 +15,284 @@
 
 import abc
 
+from google.protobuf import descriptor
 import six
 
 import grpc
 
 
+class UnaryUnaryChannelRpc(six.with_metaclass(abc.ABCMeta)):
+    """Fixture for a unary-unary RPC invoked by a system under test.
+
+    Enables users to "play server" for the RPC.
+    """
+
+    @abc.abstractmethod
+    def send_initial_metadata(self, initial_metadata):
+        """Sends the RPC's initial metadata to the system under test.
+
+        Args:
+          initial_metadata: The RPC's initial metadata to be "sent" to
+            the system under test.
+        """
+        raise NotImplementedError()
+
+    @abc.abstractmethod
+    def cancelled(self):
+        """Blocks until the system under test has cancelled the RPC."""
+        raise NotImplementedError()
+
+    @abc.abstractmethod
+    def terminate(self, response, trailing_metadata, code, details):
+        """Terminates the RPC.
+
+        Args:
+          response: The response for the RPC.
+          trailing_metadata: The RPC's trailing metadata.
+          code: The RPC's status code.
+          details: The RPC's status details.
+        """
+        raise NotImplementedError()
+
+
+class UnaryStreamChannelRpc(six.with_metaclass(abc.ABCMeta)):
+    """Fixture for a unary-stream RPC invoked by a system under test.
+
+    Enables users to "play server" for the RPC.
+    """
+
+    @abc.abstractmethod
+    def send_initial_metadata(self, initial_metadata):
+        """Sends the RPC's initial metadata to the system under test.
+
+        Args:
+          initial_metadata: The RPC's initial metadata to be "sent" to
+            the system under test.
+        """
+        raise NotImplementedError()
+
+    @abc.abstractmethod
+    def send_response(self, response):
+        """Sends a response to the system under test.
+
+        Args:
+          response: A response message to be "sent" to the system under test.
+        """
+        raise NotImplementedError()
+
+    @abc.abstractmethod
+    def cancelled(self):
+        """Blocks until the system under test has cancelled the RPC."""
+        raise NotImplementedError()
+
+    @abc.abstractmethod
+    def terminate(self, trailing_metadata, code, details):
+        """Terminates the RPC.
+
+        Args:
+          trailing_metadata: The RPC's trailing metadata.
+          code: The RPC's status code.
+          details: The RPC's status details.
+        """
+        raise NotImplementedError()
+
+
+class StreamUnaryChannelRpc(six.with_metaclass(abc.ABCMeta)):
+    """Fixture for a stream-unary RPC invoked by a system under test.
+
+    Enables users to "play server" for the RPC.
+    """
+
+    @abc.abstractmethod
+    def send_initial_metadata(self, initial_metadata):
+        """Sends the RPC's initial metadata to the system under test.
+
+        Args:
+          initial_metadata: The RPC's initial metadata to be "sent" to
+            the system under test.
+        """
+        raise NotImplementedError()
+
+    @abc.abstractmethod
+    def take_request(self):
+        """Draws one of the requests added to the RPC by the system under test.
+
+        This method blocks until the system under test has added to the RPC
+        the request to be returned.
+
+        Successive calls to this method return requests in the same order in
+        which the system under test added them to the RPC.
+
+        Returns:
+          A request message added to the RPC by the system under test.
+        """
+        raise NotImplementedError()
+
+    @abc.abstractmethod
+    def requests_closed(self):
+        """Blocks until the system under test has closed the request stream."""
+        raise NotImplementedError()
+
+    @abc.abstractmethod
+    def cancelled(self):
+        """Blocks until the system under test has cancelled the RPC."""
+        raise NotImplementedError()
+
+    @abc.abstractmethod
+    def terminate(self, response, trailing_metadata, code, details):
+        """Terminates the RPC.
+
+        Args:
+          response: The response for the RPC.
+          trailing_metadata: The RPC's trailing metadata.
+          code: The RPC's status code.
+          details: The RPC's status details.
+        """
+        raise NotImplementedError()
+
+
+class StreamStreamChannelRpc(six.with_metaclass(abc.ABCMeta)):
+    """Fixture for a stream-stream RPC invoked by a system under test.
+
+    Enables users to "play server" for the RPC.
+    """
+
+    @abc.abstractmethod
+    def send_initial_metadata(self, initial_metadata):
+        """Sends the RPC's initial metadata to the system under test.
+
+        Args:
+          initial_metadata: The RPC's initial metadata to be "sent" to the
+            system under test.
+        """
+        raise NotImplementedError()
+
+    @abc.abstractmethod
+    def take_request(self):
+        """Draws one of the requests added to the RPC by the system under test.
+
+        This method blocks until the system under test has added to the RPC
+        the request to be returned.
+
+        Successive calls to this method return requests in the same order in
+        which the system under test added them to the RPC.
+
+        Returns:
+          A request message added to the RPC by the system under test.
+        """
+        raise NotImplementedError()
+
+    @abc.abstractmethod
+    def send_response(self, response):
+        """Sends a response to the system under test.
+
+        Args:
+          response: A response messages to be "sent" to the system under test.
+        """
+        raise NotImplementedError()
+
+    @abc.abstractmethod
+    def requests_closed(self):
+        """Blocks until the system under test has closed the request stream."""
+        raise NotImplementedError()
+
+    @abc.abstractmethod
+    def cancelled(self):
+        """Blocks until the system under test has cancelled the RPC."""
+        raise NotImplementedError()
+
+    @abc.abstractmethod
+    def terminate(self, trailing_metadata, code, details):
+        """Terminates the RPC.
+
+        Args:
+          trailing_metadata: The RPC's trailing metadata.
+          code: The RPC's status code.
+          details: The RPC's status details.
+        """
+        raise NotImplementedError()
+
+
+class Channel(six.with_metaclass(abc.ABCMeta), grpc.Channel):
+    """A grpc.Channel double with which to test a system that invokes RPCs."""
+
+    @abc.abstractmethod
+    def take_unary_unary(self, method_descriptor):
+        """Draws an RPC currently being made by the system under test.
+
+        If the given descriptor does not identify any RPC currently being made
+        by the system under test, this method blocks until the system under
+        test invokes such an RPC.
+
+        Args:
+          method_descriptor: A descriptor.MethodDescriptor describing a
+            unary-unary RPC method.
+
+        Returns:
+          A (invocation_metadata, request, unary_unary_channel_rpc) tuple of
+            the RPC's invocation metadata, its request, and a
+            UnaryUnaryChannelRpc with which to "play server" for the RPC.
+        """
+        raise NotImplementedError()
+
+    @abc.abstractmethod
+    def take_unary_stream(self, method_descriptor):
+        """Draws an RPC currently being made by the system under test.
+
+        If the given descriptor does not identify any RPC currently being made
+        by the system under test, this method blocks until the system under
+        test invokes such an RPC.
+
+        Args:
+          method_descriptor: A descriptor.MethodDescriptor describing a
+            unary-stream RPC method.
+
+        Returns:
+          A (invocation_metadata, request, unary_stream_channel_rpc) tuple of
+            the RPC's invocation metadata, its request, and a
+            UnaryStreamChannelRpc with which to "play server" for the RPC.
+        """
+        raise NotImplementedError()
+
+    @abc.abstractmethod
+    def take_stream_unary(self, method_descriptor):
+        """Draws an RPC currently being made by the system under test.
+
+        If the given descriptor does not identify any RPC currently being made
+        by the system under test, this method blocks until the system under
+        test invokes such an RPC.
+
+        Args:
+          method_descriptor: A descriptor.MethodDescriptor describing a
+            stream-unary RPC method.
+
+        Returns:
+          A (invocation_metadata, stream_unary_channel_rpc) tuple of the RPC's
+            invocation metadata and a StreamUnaryChannelRpc with which to "play
+            server" for the RPC.
+        """
+        raise NotImplementedError()
+
+    @abc.abstractmethod
+    def take_stream_stream(self, method_descriptor):
+        """Draws an RPC currently being made by the system under test.
+
+        If the given descriptor does not identify any RPC currently being made
+        by the system under test, this method blocks until the system under
+        test invokes such an RPC.
+
+        Args:
+          method_descriptor: A descriptor.MethodDescriptor describing a
+            stream-stream RPC method.
+
+        Returns:
+          A (invocation_metadata, stream_stream_channel_rpc) tuple of the RPC's
+            invocation metadata and a StreamStreamChannelRpc with which to
+            "play server" for the RPC.
+        """
+        raise NotImplementedError()
+
+
 class Time(six.with_metaclass(abc.ABCMeta)):
     """A simulation of time.
 
@@ -117,3 +390,19 @@
     """
     from grpc_testing import _time
     return _time.StrictFakeTime(now)
+
+
+def channel(service_descriptors, time):
+    """Creates a Channel for use in tests of a gRPC Python-using system.
+
+    Args:
+      service_descriptors: An iterable of descriptor.ServiceDescriptors
+        describing the RPCs that will be made on the returned Channel by the
+        system under test.
+      time: A Time to be used for tests.
+
+    Returns:
+      A Channel for use in tests.
+    """
+    from grpc_testing import _channel
+    return _channel.testing_channel(service_descriptors, time)
diff --git a/src/python/grpcio_testing/grpc_testing/_channel/__init__.py b/src/python/grpcio_testing/grpc_testing/_channel/__init__.py
new file mode 100644
index 0000000..8011975
--- /dev/null
+++ b/src/python/grpcio_testing/grpc_testing/_channel/__init__.py
@@ -0,0 +1,23 @@
+# Copyright 2017 gRPC authors.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+from grpc_testing._channel import _channel
+from grpc_testing._channel import _channel_state
+
+
+# descriptors is reserved for later use.
+# pylint: disable=unused-argument
+def testing_channel(descriptors, time):
+    return _channel.TestingChannel(time, _channel_state.State())
+# pylint: enable=unused-argument
diff --git a/src/python/grpcio_testing/grpc_testing/_channel/_channel.py b/src/python/grpcio_testing/grpc_testing/_channel/_channel.py
new file mode 100644
index 0000000..fbd064d
--- /dev/null
+++ b/src/python/grpcio_testing/grpc_testing/_channel/_channel.py
@@ -0,0 +1,62 @@
+# Copyright 2017 gRPC authors.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import grpc_testing
+from grpc_testing._channel import _channel_rpc
+from grpc_testing._channel import _multi_callable
+
+
+# All serializer and deserializer parameters are not (yet) used by this
+# test infrastructure.
+# pylint: disable=unused-argument
+class TestingChannel(grpc_testing.Channel):
+
+    def __init__(self, time, state):
+        self._time = time
+        self._state = state
+
+    def subscribe(self, callback, try_to_connect=False):
+        raise NotImplementedError()
+
+    def unsubscribe(self, callback):
+        raise NotImplementedError()
+
+    def unary_unary(
+            self, method, request_serializer=None, response_deserializer=None):
+        return _multi_callable.UnaryUnary(method, self._state)
+
+    def unary_stream(
+            self, method, request_serializer=None, response_deserializer=None):
+        return _multi_callable.UnaryStream(method, self._state)
+
+    def stream_unary(
+            self, method, request_serializer=None, response_deserializer=None):
+        return _multi_callable.StreamUnary(method, self._state)
+
+    def stream_stream(
+            self, method, request_serializer=None, response_deserializer=None):
+        return _multi_callable.StreamStream(method, self._state)
+
+    def take_unary_unary(self, method_descriptor):
+        return _channel_rpc.unary_unary(self._state, method_descriptor)
+
+    def take_unary_stream(self, method_descriptor):
+        return _channel_rpc.unary_stream(self._state, method_descriptor)
+
+    def take_stream_unary(self, method_descriptor):
+        return _channel_rpc.stream_unary(self._state, method_descriptor)
+
+    def take_stream_stream(self, method_descriptor):
+        return _channel_rpc.stream_stream(self._state, method_descriptor)
+# pylint: enable=unused-argument
diff --git a/src/python/grpcio_testing/grpc_testing/_channel/_channel_rpc.py b/src/python/grpcio_testing/grpc_testing/_channel/_channel_rpc.py
new file mode 100644
index 0000000..762b6a0
--- /dev/null
+++ b/src/python/grpcio_testing/grpc_testing/_channel/_channel_rpc.py
@@ -0,0 +1,119 @@
+# Copyright 2017 gRPC authors.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import grpc_testing
+
+
+class _UnaryUnary(grpc_testing.UnaryUnaryChannelRpc):
+
+    def __init__(self, rpc_state):
+        self._rpc_state = rpc_state
+
+    def send_initial_metadata(self, initial_metadata):
+        self._rpc_state.send_initial_metadata(initial_metadata)
+
+    def cancelled(self):
+        self._rpc_state.cancelled()
+
+    def terminate(self, response, trailing_metadata, code, details):
+        self._rpc_state.terminate_with_response(
+            response, trailing_metadata, code, details)
+
+
+class _UnaryStream(grpc_testing.UnaryStreamChannelRpc):
+
+    def __init__(self, rpc_state):
+        self._rpc_state = rpc_state
+
+    def send_initial_metadata(self, initial_metadata):
+        self._rpc_state.send_initial_metadata(initial_metadata)
+
+    def send_response(self, response):
+        self._rpc_state.send_response(response)
+
+    def cancelled(self):
+        self._rpc_state.cancelled()
+
+    def terminate(self, trailing_metadata, code, details):
+        self._rpc_state.terminate(trailing_metadata, code, details)
+
+
+class _StreamUnary(grpc_testing.StreamUnaryChannelRpc):
+
+    def __init__(self, rpc_state):
+        self._rpc_state = rpc_state
+
+    def send_initial_metadata(self, initial_metadata):
+        self._rpc_state.send_initial_metadata(initial_metadata)
+
+    def take_request(self):
+        return self._rpc_state.take_request()
+
+    def requests_closed(self):
+        return self._rpc_state.requests_closed()
+
+    def cancelled(self):
+        self._rpc_state.cancelled()
+
+    def terminate(self, response, trailing_metadata, code, details):
+        self._rpc_state.terminate_with_response(
+            response, trailing_metadata, code, details)
+
+
+class _StreamStream(grpc_testing.StreamStreamChannelRpc):
+
+    def __init__(self, rpc_state):
+        self._rpc_state = rpc_state
+
+    def send_initial_metadata(self, initial_metadata):
+        self._rpc_state.send_initial_metadata(initial_metadata)
+
+    def take_request(self):
+        return self._rpc_state.take_request()
+
+    def send_response(self, response):
+        self._rpc_state.send_response(response)
+
+    def requests_closed(self):
+        return self._rpc_state.requests_closed()
+
+    def cancelled(self):
+        self._rpc_state.cancelled()
+
+    def terminate(self, trailing_metadata, code, details):
+        self._rpc_state.terminate(trailing_metadata, code, details)
+
+
+def unary_unary(channel_state, method_descriptor):
+    rpc_state = channel_state.take_rpc_state(method_descriptor)
+    invocation_metadata, request = (
+        rpc_state.take_invocation_metadata_and_request())
+    return invocation_metadata, request, _UnaryUnary(rpc_state)
+
+
+def unary_stream(channel_state, method_descriptor):
+    rpc_state = channel_state.take_rpc_state(method_descriptor)
+    invocation_metadata, request = (
+        rpc_state.take_invocation_metadata_and_request())
+    return invocation_metadata, request, _UnaryStream(rpc_state)
+
+
+def stream_unary(channel_state, method_descriptor):
+    rpc_state = channel_state.take_rpc_state(method_descriptor)
+    return rpc_state.take_invocation_metadata(), _StreamUnary(rpc_state)
+
+
+def stream_stream(channel_state, method_descriptor):
+    rpc_state = channel_state.take_rpc_state(method_descriptor)
+    return rpc_state.take_invocation_metadata(), _StreamStream(rpc_state)
diff --git a/src/python/grpcio_testing/grpc_testing/_channel/_channel_state.py b/src/python/grpcio_testing/grpc_testing/_channel/_channel_state.py
new file mode 100644
index 0000000..569c41d
--- /dev/null
+++ b/src/python/grpcio_testing/grpc_testing/_channel/_channel_state.py
@@ -0,0 +1,48 @@
+# Copyright 2017 gRPC authors.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import collections
+import threading
+
+from grpc_testing import _common
+from grpc_testing._channel import _rpc_state
+
+
+class State(_common.ChannelHandler):
+
+    def __init__(self):
+        self._condition = threading.Condition()
+        self._rpc_states = collections.defaultdict(list)
+
+    def invoke_rpc(
+            self, method_full_rpc_name, invocation_metadata, requests,
+            requests_closed, timeout):
+        rpc_state = _rpc_state.State(
+            invocation_metadata, requests, requests_closed)
+        with self._condition:
+            self._rpc_states[method_full_rpc_name].append(rpc_state)
+            self._condition.notify_all()
+        return rpc_state
+
+    def take_rpc_state(self, method_descriptor):
+        method_full_rpc_name = '/{}/{}'.format(
+            method_descriptor.containing_service.full_name,
+            method_descriptor.name)
+        with self._condition:
+            while True:
+                method_rpc_states = self._rpc_states[method_full_rpc_name]
+                if method_rpc_states:
+                    return method_rpc_states.pop(0)
+                else:
+                    self._condition.wait()
diff --git a/src/python/grpcio_testing/grpc_testing/_channel/_invocation.py b/src/python/grpcio_testing/grpc_testing/_channel/_invocation.py
new file mode 100644
index 0000000..ebce652
--- /dev/null
+++ b/src/python/grpcio_testing/grpc_testing/_channel/_invocation.py
@@ -0,0 +1,322 @@
+# Copyright 2017 gRPC authors.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import logging
+import threading
+
+import grpc
+
+_NOT_YET_OBSERVED = object()
+
+
+def _cancel(handler):
+    return handler.cancel(grpc.StatusCode.CANCELLED, 'Locally cancelled!')
+
+
+def _is_active(handler):
+    return handler.is_active()
+
+
+def _time_remaining(unused_handler):
+    raise NotImplementedError()
+
+
+def _add_callback(handler, callback):
+    return handler.add_callback(callback)
+
+
+def _initial_metadata(handler):
+    return handler.initial_metadata()
+
+
+def _trailing_metadata(handler):
+    trailing_metadata, unused_code, unused_details = handler.termination()
+    return trailing_metadata
+
+
+def _code(handler):
+    unused_trailing_metadata, code, unused_details = handler.termination()
+    return code
+
+
+def _details(handler):
+    unused_trailing_metadata, unused_code, details = handler.termination()
+    return details
+
+
+class _Call(grpc.Call):
+
+    def __init__(self, handler):
+        self._handler = handler
+
+    def cancel(self):
+        _cancel(self._handler)
+
+    def is_active(self):
+        return _is_active(self._handler)
+
+    def time_remaining(self):
+        return _time_remaining(self._handler)
+
+    def add_callback(self, callback):
+        return _add_callback(self._handler, callback)
+
+    def initial_metadata(self):
+        return _initial_metadata(self._handler)
+
+    def trailing_metadata(self):
+        return _trailing_metadata(self._handler)
+
+    def code(self):
+        return _code(self._handler)
+
+    def details(self):
+        return _details(self._handler)
+
+
+class _RpcErrorCall(grpc.RpcError, grpc.Call):
+
+    def __init__(self, handler):
+        self._handler = handler
+
+    def cancel(self):
+        _cancel(self._handler)
+
+    def is_active(self):
+        return _is_active(self._handler)
+
+    def time_remaining(self):
+        return _time_remaining(self._handler)
+
+    def add_callback(self, callback):
+        return _add_callback(self._handler, callback)
+
+    def initial_metadata(self):
+        return _initial_metadata(self._handler)
+
+    def trailing_metadata(self):
+        return _trailing_metadata(self._handler)
+
+    def code(self):
+        return _code(self._handler)
+
+    def details(self):
+        return _details(self._handler)
+
+
+def _next(handler):
+    read = handler.take_response()
+    if read.code is None:
+        return read.response
+    elif read.code is grpc.StatusCode.OK:
+        raise StopIteration()
+    else:
+        raise _RpcErrorCall(handler)
+
+
+class _HandlerExtras(object):
+
+    def __init__(self):
+        self.condition = threading.Condition()
+        self.unary_response = _NOT_YET_OBSERVED
+        self.cancelled = False
+
+
+def _with_extras_cancel(handler, extras):
+    with extras.condition:
+        if handler.cancel(grpc.StatusCode.CANCELLED, 'Locally cancelled!'):
+            extras.cancelled = True
+            return True
+        else:
+            return False
+
+
+def _extras_without_cancelled(extras):
+    with extras.condition:
+        return extras.cancelled
+
+
+def _running(handler):
+    return handler.is_active()
+
+
+def _done(handler):
+    return not handler.is_active()
+
+
+def _with_extras_unary_response(handler, extras):
+    with extras.condition:
+        if extras.unary_response is _NOT_YET_OBSERVED:
+            read = handler.take_response()
+            if read.code is None:
+                extras.unary_response = read.response
+                return read.response
+            else:
+                raise _RpcErrorCall(handler)
+        else:
+            return extras.unary_response
+
+
+def _exception(unused_handler):
+    raise NotImplementedError('TODO!')
+
+
+def _traceback(unused_handler):
+    raise NotImplementedError('TODO!')
+
+
+def _add_done_callback(handler, callback, future):
+    adapted_callback = lambda: callback(future)
+    if not handler.add_callback(adapted_callback):
+        callback(future)
+
+
+class _FutureCall(grpc.Future, grpc.Call):
+
+    def __init__(self, handler, extras):
+        self._handler = handler
+        self._extras = extras
+
+    def cancel(self):
+        return _with_extras_cancel(self._handler, self._extras)
+
+    def cancelled(self):
+        return _extras_without_cancelled(self._extras)
+
+    def running(self):
+        return _running(self._handler)
+
+    def done(self):
+        return _done(self._handler)
+
+    def result(self):
+        return _with_extras_unary_response(self._handler, self._extras)
+
+    def exception(self):
+        return _exception(self._handler)
+
+    def traceback(self):
+        return _traceback(self._handler)
+
+    def add_done_callback(self, fn):
+        _add_done_callback(self._handler, fn, self)
+
+    def is_active(self):
+        return _is_active(self._handler)
+
+    def time_remaining(self):
+        return _time_remaining(self._handler)
+
+    def add_callback(self, callback):
+        return _add_callback(self._handler, callback)
+
+    def initial_metadata(self):
+        return _initial_metadata(self._handler)
+
+    def trailing_metadata(self):
+        return _trailing_metadata(self._handler)
+
+    def code(self):
+        return _code(self._handler)
+
+    def details(self):
+        return _details(self._handler)
+
+
+def consume_requests(request_iterator, handler):
+
+    def _consume():
+        while True:
+            try:
+                request = next(request_iterator)
+                added = handler.add_request(request)
+                if not added:
+                    break
+            except StopIteration:
+                handler.close_requests()
+                break
+            except Exception:  # pylint: disable=broad-except
+                details = 'Exception iterating requests!'
+                logging.exception(details)
+                handler.cancel(grpc.StatusCode.UNKNOWN, details)
+
+    consumption = threading.Thread(target=_consume)
+    consumption.start()
+
+
+def blocking_unary_response(handler):
+    read = handler.take_response()
+    if read.code is None:
+        unused_trailing_metadata, code, unused_details = handler.termination()
+        if code is grpc.StatusCode.OK:
+            return read.response
+        else:
+            raise _RpcErrorCall(handler)
+    else:
+        raise _RpcErrorCall(handler)
+
+
+def blocking_unary_response_with_call(handler):
+    read = handler.take_response()
+    if read.code is None:
+        unused_trailing_metadata, code, unused_details = handler.termination()
+        if code is grpc.StatusCode.OK:
+            return read.response, _Call(handler)
+        else:
+            raise _RpcErrorCall(handler)
+    else:
+        raise _RpcErrorCall(handler)
+
+
+def future_call(handler):
+    return _FutureCall(handler, _HandlerExtras())
+
+
+class ResponseIteratorCall(grpc.Call):
+
+    def __init__(self, handler):
+        self._handler = handler
+
+    def __iter__(self):
+        return self
+
+    def __next__(self):
+        return _next(self._handler)
+
+    def next(self):
+        return _next(self._handler)
+
+    def cancel(self):
+        _cancel(self._handler)
+
+    def is_active(self):
+        return _is_active(self._handler)
+
+    def time_remaining(self):
+        return _time_remaining(self._handler)
+
+    def add_callback(self, callback):
+        return _add_callback(self._handler, callback)
+
+    def initial_metadata(self):
+        return _initial_metadata(self._handler)
+
+    def trailing_metadata(self):
+        return _trailing_metadata(self._handler)
+
+    def code(self):
+        return _code(self._handler)
+
+    def details(self):
+        return _details(self._handler)
diff --git a/src/python/grpcio_testing/grpc_testing/_channel/_multi_callable.py b/src/python/grpcio_testing/grpc_testing/_channel/_multi_callable.py
new file mode 100644
index 0000000..fe69257
--- /dev/null
+++ b/src/python/grpcio_testing/grpc_testing/_channel/_multi_callable.py
@@ -0,0 +1,115 @@
+# Copyright 2017 gRPC authors.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import grpc
+from grpc_testing import _common
+from grpc_testing._channel import _invocation
+
+# All per-call credentials parameters are unused by this test infrastructure.
+# pylint: disable=unused-argument
+class UnaryUnary(grpc.UnaryUnaryMultiCallable):
+
+    def __init__(self, method_full_rpc_name, channel_handler):
+        self._method_full_rpc_name = method_full_rpc_name
+        self._channel_handler = channel_handler
+
+    def __call__(self, request, timeout=None, metadata=None, credentials=None):
+        rpc_handler = self._channel_handler.invoke_rpc(
+            self._method_full_rpc_name, _common.fuss_with_metadata(metadata),
+            [request], True, timeout)
+        return _invocation.blocking_unary_response(rpc_handler)
+
+    def with_call(self, request, timeout=None, metadata=None, credentials=None):
+        rpc_handler = self._channel_handler.invoke_rpc(
+            self._method_full_rpc_name, _common.fuss_with_metadata(metadata),
+            [request], True, timeout)
+        return _invocation.blocking_unary_response_with_call(rpc_handler)
+
+    def future(self, request, timeout=None, metadata=None, credentials=None):
+        rpc_handler = self._channel_handler.invoke_rpc(
+            self._method_full_rpc_name, _common.fuss_with_metadata(metadata),
+            [request], True, timeout)
+        return _invocation.future_call(rpc_handler)
+
+
+class UnaryStream(grpc.StreamStreamMultiCallable):
+
+    def __init__(self, method_full_rpc_name, channel_handler):
+        self._method_full_rpc_name = method_full_rpc_name
+        self._channel_handler = channel_handler
+
+    def __call__(self, request, timeout=None, metadata=None, credentials=None):
+        rpc_handler = self._channel_handler.invoke_rpc(
+            self._method_full_rpc_name,
+            _common.fuss_with_metadata(metadata), [request], True, timeout)
+        return _invocation.ResponseIteratorCall(rpc_handler)
+
+
+class StreamUnary(grpc.StreamUnaryMultiCallable):
+
+    def __init__(self, method_full_rpc_name, channel_handler):
+        self._method_full_rpc_name = method_full_rpc_name
+        self._channel_handler = channel_handler
+
+    def __call__(self,
+                 request_iterator,
+                 timeout=None,
+                 metadata=None,
+                 credentials=None):
+        rpc_handler = self._channel_handler.invoke_rpc(
+            self._method_full_rpc_name,
+            _common.fuss_with_metadata(metadata), [], False, timeout)
+        _invocation.consume_requests(request_iterator, rpc_handler)
+        return _invocation.blocking_unary_response(rpc_handler)
+
+    def with_call(self,
+                  request_iterator,
+                  timeout=None,
+                  metadata=None,
+                  credentials=None):
+        rpc_handler = self._channel_handler.invoke_rpc(
+            self._method_full_rpc_name,
+            _common.fuss_with_metadata(metadata), [], False, timeout)
+        _invocation.consume_requests(request_iterator, rpc_handler)
+        return _invocation.blocking_unary_response_with_call(rpc_handler)
+
+    def future(self,
+               request_iterator,
+               timeout=None,
+               metadata=None,
+               credentials=None):
+        rpc_handler = self._channel_handler.invoke_rpc(
+            self._method_full_rpc_name,
+            _common.fuss_with_metadata(metadata), [], False, timeout)
+        _invocation.consume_requests(request_iterator, rpc_handler)
+        return _invocation.future_call(rpc_handler)
+
+
+class StreamStream(grpc.StreamStreamMultiCallable):
+
+    def __init__(self, method_full_rpc_name, channel_handler):
+        self._method_full_rpc_name = method_full_rpc_name
+        self._channel_handler = channel_handler
+
+    def __call__(self,
+                 request_iterator,
+                 timeout=None,
+                 metadata=None,
+                 credentials=None):
+        rpc_handler = self._channel_handler.invoke_rpc(
+            self._method_full_rpc_name,
+            _common.fuss_with_metadata(metadata), [], False, timeout)
+        _invocation.consume_requests(request_iterator, rpc_handler)
+        return _invocation.ResponseIteratorCall(rpc_handler)
+# pylint: enable=unused-argument
diff --git a/src/python/grpcio_testing/grpc_testing/_channel/_rpc_state.py b/src/python/grpcio_testing/grpc_testing/_channel/_rpc_state.py
new file mode 100644
index 0000000..e1fa49a
--- /dev/null
+++ b/src/python/grpcio_testing/grpc_testing/_channel/_rpc_state.py
@@ -0,0 +1,193 @@
+# Copyright 2017 gRPC authors.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import threading
+
+import grpc
+from grpc_testing import _common
+
+
+class State(_common.ChannelRpcHandler):
+
+    def __init__(self, invocation_metadata, requests, requests_closed):
+        self._condition = threading.Condition()
+        self._invocation_metadata = invocation_metadata
+        self._requests = requests
+        self._requests_closed = requests_closed
+        self._initial_metadata = None
+        self._responses = []
+        self._trailing_metadata = None
+        self._code = None
+        self._details = None
+
+    def initial_metadata(self):
+        with self._condition:
+            while True:
+                if self._initial_metadata is None:
+                    if self._code is None:
+                        self._condition.wait()
+                    else:
+                        return _common.FUSSED_EMPTY_METADATA
+                else:
+                    return self._initial_metadata
+
+    def add_request(self, request):
+        with self._condition:
+            if self._code is None and not self._requests_closed:
+                self._requests.append(request)
+                self._condition.notify_all()
+                return True
+            else:
+                return False
+
+    def close_requests(self):
+        with self._condition:
+            if self._code is None and not self._requests_closed:
+                self._requests_closed = True
+                self._condition.notify_all()
+
+    def take_response(self):
+        with self._condition:
+            while True:
+                if self._code is grpc.StatusCode.OK:
+                    if self._responses:
+                        response = self._responses.pop(0)
+                        return _common.ChannelRpcRead(
+                            response, None, None, None)
+                    else:
+                        return _common.ChannelRpcRead(
+                            None, self._trailing_metadata,
+                            grpc.StatusCode.OK, self._details)
+                elif self._code is None:
+                    if self._responses:
+                        response = self._responses.pop(0)
+                        return _common.ChannelRpcRead(
+                            response, None, None, None)
+                    else:
+                        self._condition.wait()
+                else:
+                    return _common.ChannelRpcRead(
+                        None, self._trailing_metadata, self._code,
+                        self._details)
+
+    def termination(self):
+        with self._condition:
+            while True:
+                if self._code is None:
+                    self._condition.wait()
+                else:
+                    return self._trailing_metadata, self._code, self._details
+
+    def cancel(self, code, details):
+        with self._condition:
+            if self._code is None:
+                if self._initial_metadata is None:
+                    self._initial_metadata = _common.FUSSED_EMPTY_METADATA
+                self._trailing_metadata = _common.FUSSED_EMPTY_METADATA
+                self._code = code
+                self._details = details
+                self._condition.notify_all()
+                return True
+            else:
+                return False
+
+    def take_invocation_metadata(self):
+        with self._condition:
+            if self._invocation_metadata is None:
+                raise ValueError('Expected invocation metadata!')
+            else:
+                invocation_metadata = self._invocation_metadata
+                self._invocation_metadata = None
+                return invocation_metadata
+
+    def take_invocation_metadata_and_request(self):
+        with self._condition:
+            if self._invocation_metadata is None:
+                raise ValueError('Expected invocation metadata!')
+            elif not self._requests:
+                raise ValueError('Expected at least one request!')
+            else:
+                invocation_metadata = self._invocation_metadata
+                self._invocation_metadata = None
+                return invocation_metadata, self._requests.pop(0)
+
+    def send_initial_metadata(self, initial_metadata):
+        with self._condition:
+            self._initial_metadata = _common.fuss_with_metadata(
+                initial_metadata)
+            self._condition.notify_all()
+
+    def take_request(self):
+        with self._condition:
+            while True:
+                if self._requests:
+                    return self._requests.pop(0)
+                else:
+                    self._condition.wait()
+
+    def requests_closed(self):
+        with self._condition:
+            while True:
+                if self._requests_closed:
+                    return
+                else:
+                    self._condition.wait()
+
+    def send_response(self, response):
+        with self._condition:
+            if self._code is None:
+                self._responses.append(response)
+                self._condition.notify_all()
+
+    def terminate_with_response(
+            self, response, trailing_metadata, code, details):
+        with self._condition:
+            if self._initial_metadata is None:
+                self._initial_metadata = _common.FUSSED_EMPTY_METADATA
+            self._responses.append(response)
+            self._trailing_metadata = _common.fuss_with_metadata(
+                trailing_metadata)
+            self._code = code
+            self._details = details
+            self._condition.notify_all()
+
+    def terminate(self, trailing_metadata, code, details):
+        with self._condition:
+            if self._initial_metadata is None:
+                self._initial_metadata = _common.FUSSED_EMPTY_METADATA
+            self._trailing_metadata = _common.fuss_with_metadata(
+                trailing_metadata)
+            self._code = code
+            self._details = details
+            self._condition.notify_all()
+
+    def cancelled(self):
+        with self._condition:
+            while True:
+                if self._code is grpc.StatusCode.CANCELLED:
+                    return
+                elif self._code is None:
+                    self._condition.wait()
+                else:
+                    raise ValueError(
+                        'Status code unexpectedly {}!'.format(self._code))
+
+    def is_active(self):
+        raise NotImplementedError()
+
+    def time_remaining(self):
+        raise NotImplementedError()
+
+    def add_callback(self, callback):
+        raise NotImplementedError()
diff --git a/src/python/grpcio_testing/grpc_testing/_common.py b/src/python/grpcio_testing/grpc_testing/_common.py
new file mode 100644
index 0000000..cb4a7f5
--- /dev/null
+++ b/src/python/grpcio_testing/grpc_testing/_common.py
@@ -0,0 +1,92 @@
+# Copyright 2017 gRPC authors.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+"""Common interfaces and implementation."""
+
+import abc
+import collections
+
+import six
+
+
+def _fuss(tuplified_metadata):
+    return tuplified_metadata + (
+        (
+            'grpc.metadata_added_by_runtime',
+            'gRPC is allowed to add metadata in transmission and does so.',
+        ),
+    )
+
+FUSSED_EMPTY_METADATA = _fuss(())
+
+
+def fuss_with_metadata(metadata):
+    if metadata is None:
+        return FUSSED_EMPTY_METADATA
+    else:
+        return _fuss(tuple(metadata))
+
+
+class ChannelRpcRead(
+        collections.namedtuple(
+            'ChannelRpcRead',
+            ('response', 'trailing_metadata', 'code', 'details',))):
+    pass
+
+
+class ChannelRpcHandler(six.with_metaclass(abc.ABCMeta)):
+
+    @abc.abstractmethod
+    def initial_metadata(self):
+        raise NotImplementedError()
+
+    @abc.abstractmethod
+    def add_request(self, request):
+        raise NotImplementedError()
+
+    @abc.abstractmethod
+    def close_requests(self):
+        raise NotImplementedError()
+
+    @abc.abstractmethod
+    def take_response(self):
+        raise NotImplementedError()
+
+    @abc.abstractmethod
+    def cancel(self, code, details):
+        raise NotImplementedError()
+
+    @abc.abstractmethod
+    def termination(self):
+        raise NotImplementedError()
+
+    @abc.abstractmethod
+    def is_active(self):
+        raise NotImplementedError()
+
+    @abc.abstractmethod
+    def time_remaining(self):
+        raise NotImplementedError()
+
+    @abc.abstractmethod
+    def add_callback(self, callback):
+        raise NotImplementedError()
+
+
+class ChannelHandler(six.with_metaclass(abc.ABCMeta)):
+
+    @abc.abstractmethod
+    def invoke_rpc(
+            self, method_full_rpc_name, invocation_metadata, requests,
+            requests_closed, timeout):
+        raise NotImplementedError()
diff --git a/src/python/grpcio_tests/setup.py b/src/python/grpcio_tests/setup.py
index adc909c..debe14c 100644
--- a/src/python/grpcio_tests/setup.py
+++ b/src/python/grpcio_tests/setup.py
@@ -68,6 +68,10 @@
     'tests.protoc_plugin.protos.invocation_testing.split_services': [
         'services.proto',
     ],
+    'tests.testing.proto': [
+        'requests.proto',
+        'services.proto',
+    ],
     'tests.unit': [
         'credentials/ca.pem',
         'credentials/server1.key',
diff --git a/src/python/grpcio_tests/tests/testing/_application_common.py b/src/python/grpcio_tests/tests/testing/_application_common.py
new file mode 100644
index 0000000..4e98879
--- /dev/null
+++ b/src/python/grpcio_tests/tests/testing/_application_common.py
@@ -0,0 +1,36 @@
+# Copyright 2017 gRPC authors.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+"""An example gRPC Python-using application's common code elements."""
+
+from tests.testing.proto import requests_pb2
+from tests.testing.proto import services_pb2
+
+SERVICE_NAME = 'tests_of_grpc_testing.FirstService'
+UNARY_UNARY_METHOD_NAME = 'UnUn'
+UNARY_STREAM_METHOD_NAME = 'UnStre'
+STREAM_UNARY_METHOD_NAME = 'StreUn'
+STREAM_STREAM_METHOD_NAME = 'StreStre'
+
+UNARY_UNARY_REQUEST = requests_pb2.Up(first_up_field=2)
+ERRONEOUS_UNARY_UNARY_REQUEST = requests_pb2.Up(first_up_field=3)
+UNARY_UNARY_RESPONSE = services_pb2.Down(first_down_field=5)
+ERRONEOUS_UNARY_UNARY_RESPONSE = services_pb2.Down(first_down_field=7)
+UNARY_STREAM_REQUEST = requests_pb2.Charm(first_charm_field=11)
+STREAM_UNARY_REQUEST = requests_pb2.Charm(first_charm_field=13)
+STREAM_UNARY_RESPONSE = services_pb2.Strange(first_strange_field=17)
+STREAM_STREAM_REQUEST = requests_pb2.Top(first_top_field=19)
+STREAM_STREAM_RESPONSE = services_pb2.Bottom(first_bottom_field=23)
+TWO_STREAM_STREAM_RESPONSES = (STREAM_STREAM_RESPONSE,) * 2
+
+INFINITE_REQUEST_STREAM_TIMEOUT = 0.2
diff --git a/src/python/grpcio_tests/tests/testing/_application_testing_common.py b/src/python/grpcio_tests/tests/testing/_application_testing_common.py
new file mode 100644
index 0000000..9c9e485
--- /dev/null
+++ b/src/python/grpcio_tests/tests/testing/_application_testing_common.py
@@ -0,0 +1,33 @@
+# Copyright 2017 gRPC authors.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import grpc_testing
+
+from tests.testing.proto import requests_pb2
+from tests.testing.proto import services_pb2
+
+# TODO(https://github.com/grpc/grpc/issues/11657): Eliminate this entirely.
+# TODO(https://github.com/google/protobuf/issues/3452): Eliminate this if/else.
+if services_pb2.DESCRIPTOR.services_by_name.get('FirstService') is None:
+    FIRST_SERVICE = 'Fix protobuf issue 3452!'
+    FIRST_SERVICE_UNUN = 'Fix protobuf issue 3452!'
+    FIRST_SERVICE_UNSTRE = 'Fix protobuf issue 3452!'
+    FIRST_SERVICE_STREUN = 'Fix protobuf issue 3452!'
+    FIRST_SERVICE_STRESTRE = 'Fix protobuf issue 3452!'
+else:
+    FIRST_SERVICE = services_pb2.DESCRIPTOR.services_by_name['FirstService']
+    FIRST_SERVICE_UNUN = FIRST_SERVICE.methods_by_name['UnUn']
+    FIRST_SERVICE_UNSTRE = FIRST_SERVICE.methods_by_name['UnStre']
+    FIRST_SERVICE_STREUN = FIRST_SERVICE.methods_by_name['StreUn']
+    FIRST_SERVICE_STRESTRE = FIRST_SERVICE.methods_by_name['StreStre']
diff --git a/src/python/grpcio_tests/tests/testing/_client_application.py b/src/python/grpcio_tests/tests/testing/_client_application.py
new file mode 100644
index 0000000..aff32fb
--- /dev/null
+++ b/src/python/grpcio_tests/tests/testing/_client_application.py
@@ -0,0 +1,260 @@
+# Copyright 2017 gRPC authors.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+"""An example gRPC Python-using client-side application."""
+
+import collections
+import enum
+import threading
+import time
+
+import grpc
+from tests.unit.framework.common import test_constants
+
+from tests.testing.proto import requests_pb2
+from tests.testing.proto import services_pb2
+from tests.testing.proto import services_pb2_grpc
+
+from tests.testing import _application_common
+
+
+@enum.unique
+class Scenario(enum.Enum):
+    UNARY_UNARY = 'unary unary'
+    UNARY_STREAM = 'unary stream'
+    STREAM_UNARY = 'stream unary'
+    STREAM_STREAM = 'stream stream'
+    CONCURRENT_STREAM_UNARY = 'concurrent stream unary'
+    CONCURRENT_STREAM_STREAM = 'concurrent stream stream'
+    CANCEL_UNARY_UNARY = 'cancel unary unary'
+    CANCEL_UNARY_STREAM = 'cancel unary stream'
+    INFINITE_REQUEST_STREAM = 'infinite request stream'
+
+
+class Outcome(collections.namedtuple('Outcome', ('kind', 'code', 'details'))):
+    """Outcome of a client application scenario.
+
+    Attributes:
+      kind: A Kind value describing the overall kind of scenario execution.
+      code: A grpc.StatusCode value. Only valid if kind is Kind.RPC_ERROR.
+      details: A status details string. Only valid if kind is Kind.RPC_ERROR.
+    """
+
+    @enum.unique
+    class Kind(enum.Enum):
+        SATISFACTORY = 'satisfactory'
+        UNSATISFACTORY = 'unsatisfactory'
+        RPC_ERROR = 'rpc error'
+
+
+_SATISFACTORY_OUTCOME = Outcome(Outcome.Kind.SATISFACTORY, None, None)
+_UNSATISFACTORY_OUTCOME = Outcome(Outcome.Kind.UNSATISFACTORY, None, None)
+
+
+class _Pipe(object):
+
+    def __init__(self):
+        self._condition = threading.Condition()
+        self._values = []
+        self._open = True
+
+    def __iter__(self):
+        return self
+
+    def _next(self):
+        with self._condition:
+            while True:
+                if self._values:
+                    return self._values.pop(0)
+                elif not self._open:
+                    raise StopIteration()
+                else:
+                    self._condition.wait()
+
+    def __next__(self):  # (Python 3 Iterator Protocol)
+        return self._next()
+
+    def next(self):  # (Python 2 Iterator Protocol)
+        return self._next()
+
+    def add(self, value):
+        with self._condition:
+            self._values.append(value)
+            self._condition.notify_all()
+
+    def close(self):
+        with self._condition:
+            self._open = False
+            self._condition.notify_all()
+
+
+def _run_unary_unary(stub):
+    response = stub.UnUn(_application_common.UNARY_UNARY_REQUEST)
+    if _application_common.UNARY_UNARY_RESPONSE == response:
+        return _SATISFACTORY_OUTCOME
+    else:
+        return _UNSATISFACTORY_OUTCOME
+
+
+def _run_unary_stream(stub):
+    response_iterator = stub.UnStre(_application_common.UNARY_STREAM_REQUEST)
+    try:
+        next(response_iterator)
+    except StopIteration:
+        return _SATISFACTORY_OUTCOME
+    else:
+        return _UNSATISFACTORY_OUTCOME
+
+
+def _run_stream_unary(stub):
+    response, call = stub.StreUn.with_call(
+        iter((_application_common.STREAM_UNARY_REQUEST,) * 3))
+    if (_application_common.STREAM_UNARY_RESPONSE == response and
+            call.code() is grpc.StatusCode.OK):
+        return _SATISFACTORY_OUTCOME
+    else:
+        return _UNSATISFACTORY_OUTCOME
+
+
+def _run_stream_stream(stub):
+    request_pipe = _Pipe()
+    response_iterator = stub.StreStre(iter(request_pipe))
+    request_pipe.add(_application_common.STREAM_STREAM_REQUEST)
+    first_responses = next(response_iterator), next(response_iterator),
+    request_pipe.add(_application_common.STREAM_STREAM_REQUEST)
+    second_responses = next(response_iterator), next(response_iterator),
+    request_pipe.close()
+    try:
+        next(response_iterator)
+    except StopIteration:
+        unexpected_extra_response = False
+    else:
+        unexpected_extra_response = True
+    if (first_responses == _application_common.TWO_STREAM_STREAM_RESPONSES and
+            second_responses == _application_common.TWO_STREAM_STREAM_RESPONSES
+            and not unexpected_extra_response):
+        return _SATISFACTORY_OUTCOME
+    else:
+        return _UNSATISFACTORY_OUTCOME
+
+
+def _run_concurrent_stream_unary(stub):
+    future_calls = tuple(
+        stub.StreUn.future(
+            iter((_application_common.STREAM_UNARY_REQUEST,) * 3))
+        for _ in range(test_constants.THREAD_CONCURRENCY))
+    for future_call in future_calls:
+        if future_call.code() is grpc.StatusCode.OK:
+            response = future_call.result()
+            if _application_common.STREAM_UNARY_RESPONSE != response:
+                return _UNSATISFACTORY_OUTCOME
+        else:
+            return _UNSATISFACTORY_OUTCOME
+    else:
+        return _SATISFACTORY_OUTCOME
+
+
+def _run_concurrent_stream_stream(stub):
+    condition = threading.Condition()
+    outcomes = [None] * test_constants.RPC_CONCURRENCY
+
+    def run_stream_stream(index):
+        outcome = _run_stream_stream(stub)
+        with condition:
+            outcomes[index] = outcome
+            condition.notify()
+
+    for index in range(test_constants.RPC_CONCURRENCY):
+        thread = threading.Thread(target=run_stream_stream, args=(index,))
+        thread.start()
+    with condition:
+        while True:
+            if all(outcomes):
+                for outcome in outcomes:
+                    if outcome.kind is not Outcome.Kind.SATISFACTORY:
+                        return _UNSATISFACTORY_OUTCOME
+                else:
+                    return _SATISFACTORY_OUTCOME
+            else:
+                condition.wait()
+
+
+def _run_cancel_unary_unary(stub):
+    response_future_call = stub.UnUn.future(
+        _application_common.UNARY_UNARY_REQUEST)
+    initial_metadata = response_future_call.initial_metadata()
+    cancelled = response_future_call.cancel()
+    if initial_metadata is not None and cancelled:
+        return _SATISFACTORY_OUTCOME
+    else:
+        return _UNSATISFACTORY_OUTCOME
+
+
+def _run_infinite_request_stream(stub):
+
+    def infinite_request_iterator():
+        while True:
+            yield _application_common.STREAM_UNARY_REQUEST
+
+    response_future_call = stub.StreUn.future(
+        infinite_request_iterator(),
+        timeout=_application_common.INFINITE_REQUEST_STREAM_TIMEOUT)
+    if response_future_call.code() is grpc.StatusCode.DEADLINE_EXCEEDED:
+        return _SATISFACTORY_OUTCOME
+    else:
+        return _UNSATISFACTORY_OUTCOME
+
+
+def run(scenario, channel):
+    stub = services_pb2_grpc.FirstServiceStub(channel)
+    try:
+        if scenario is Scenario.UNARY_UNARY:
+            return _run_unary_unary(stub)
+        elif scenario is Scenario.UNARY_STREAM:
+            return _run_unary_stream(stub)
+        elif scenario is Scenario.STREAM_UNARY:
+            return _run_stream_unary(stub)
+        elif scenario is Scenario.STREAM_STREAM:
+            return _run_stream_stream(stub)
+        elif scenario is Scenario.CONCURRENT_STREAM_UNARY:
+            return _run_concurrent_stream_unary(stub)
+        elif scenario is Scenario.CONCURRENT_STREAM_STREAM:
+            return _run_concurrent_stream_stream(stub)
+        elif scenario is Scenario.CANCEL_UNARY_UNARY:
+            return _run_cancel_unary_unary(stub)
+        elif scenario is Scenario.INFINITE_REQUEST_STREAM:
+            return _run_infinite_request_stream(stub)
+    except grpc.RpcError as rpc_error:
+        return Outcome(Outcome.Kind.RPC_ERROR,
+                       rpc_error.code(), rpc_error.details())
+
+
+_IMPLEMENTATIONS = {
+    Scenario.UNARY_UNARY: _run_unary_unary,
+    Scenario.UNARY_STREAM: _run_unary_stream,
+    Scenario.STREAM_UNARY: _run_stream_unary,
+    Scenario.STREAM_STREAM: _run_stream_stream,
+    Scenario.CONCURRENT_STREAM_UNARY: _run_concurrent_stream_unary,
+    Scenario.CONCURRENT_STREAM_STREAM: _run_concurrent_stream_stream,
+    Scenario.CANCEL_UNARY_UNARY: _run_cancel_unary_unary,
+    Scenario.INFINITE_REQUEST_STREAM: _run_infinite_request_stream,
+}
+
+
+def run(scenario, channel):
+    stub = services_pb2_grpc.FirstServiceStub(channel)
+    try:
+        return _IMPLEMENTATIONS[scenario](stub)
+    except grpc.RpcError as rpc_error:
+        return Outcome(Outcome.Kind.RPC_ERROR,
+                       rpc_error.code(), rpc_error.details())
diff --git a/src/python/grpcio_tests/tests/testing/_client_test.py b/src/python/grpcio_tests/tests/testing/_client_test.py
new file mode 100644
index 0000000..172f386
--- /dev/null
+++ b/src/python/grpcio_tests/tests/testing/_client_test.py
@@ -0,0 +1,306 @@
+# Copyright 2017 gRPC authors.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+from concurrent import futures
+import time
+import unittest
+
+import grpc
+from grpc.framework.foundation import logging_pool
+from tests.unit.framework.common import test_constants
+import grpc_testing
+
+from tests.testing import _application_common
+from tests.testing import _application_testing_common
+from tests.testing import _client_application
+from tests.testing.proto import requests_pb2
+from tests.testing.proto import services_pb2
+
+
+# TODO(https://github.com/google/protobuf/issues/3452): Drop this skip.
+@unittest.skipIf(
+    services_pb2.DESCRIPTOR.services_by_name.get('FirstService') is None,
+    'Fix protobuf issue 3452!')
+class ClientTest(unittest.TestCase):
+
+    def setUp(self):
+        # In this test the client-side application under test executes in
+        # a separate thread while we retain use of the test thread to "play
+        # server".
+        self._client_execution_thread_pool = logging_pool.pool(1)
+
+        self._fake_time = grpc_testing.strict_fake_time(time.time())
+        self._real_time = grpc_testing.strict_real_time()
+        self._fake_time_channel = grpc_testing.channel(
+            services_pb2.DESCRIPTOR.services_by_name.values(), self._fake_time)
+        self._real_time_channel = grpc_testing.channel(
+            services_pb2.DESCRIPTOR.services_by_name.values(), self._real_time)
+
+    def tearDown(self):
+        self._client_execution_thread_pool.shutdown(wait=True)
+
+    def test_successful_unary_unary(self):
+        application_future = self._client_execution_thread_pool.submit(
+            _client_application.run, _client_application.Scenario.UNARY_UNARY,
+            self._real_time_channel)
+        invocation_metadata, request, rpc = (
+            self._real_time_channel.take_unary_unary(
+                _application_testing_common.FIRST_SERVICE_UNUN))
+        rpc.send_initial_metadata(())
+        rpc.terminate(_application_common.UNARY_UNARY_RESPONSE, (),
+                      grpc.StatusCode.OK, '')
+        application_return_value = application_future.result()
+
+        self.assertEqual(_application_common.UNARY_UNARY_REQUEST, request)
+        self.assertIs(application_return_value.kind,
+                      _client_application.Outcome.Kind.SATISFACTORY)
+
+    def test_successful_unary_stream(self):
+        application_future = self._client_execution_thread_pool.submit(
+            _client_application.run, _client_application.Scenario.UNARY_STREAM,
+            self._fake_time_channel)
+        invocation_metadata, request, rpc = (
+            self._fake_time_channel.take_unary_stream(
+                _application_testing_common.FIRST_SERVICE_UNSTRE))
+        rpc.send_initial_metadata(())
+        rpc.terminate((), grpc.StatusCode.OK, '')
+        application_return_value = application_future.result()
+
+        self.assertEqual(_application_common.UNARY_STREAM_REQUEST, request)
+        self.assertIs(application_return_value.kind,
+                      _client_application.Outcome.Kind.SATISFACTORY)
+
+    def test_successful_stream_unary(self):
+        application_future = self._client_execution_thread_pool.submit(
+            _client_application.run, _client_application.Scenario.STREAM_UNARY,
+            self._real_time_channel)
+        invocation_metadata, rpc = self._real_time_channel.take_stream_unary(
+            _application_testing_common.FIRST_SERVICE_STREUN)
+        rpc.send_initial_metadata(())
+        first_request = rpc.take_request()
+        second_request = rpc.take_request()
+        third_request = rpc.take_request()
+        rpc.requests_closed()
+        rpc.terminate(_application_common.STREAM_UNARY_RESPONSE, (),
+                      grpc.StatusCode.OK, '')
+        application_return_value = application_future.result()
+
+        self.assertEqual(_application_common.STREAM_UNARY_REQUEST,
+                         first_request)
+        self.assertEqual(_application_common.STREAM_UNARY_REQUEST,
+                         second_request)
+        self.assertEqual(_application_common.STREAM_UNARY_REQUEST,
+                         third_request)
+        self.assertIs(application_return_value.kind,
+                      _client_application.Outcome.Kind.SATISFACTORY)
+
+    def test_successful_stream_stream(self):
+        application_future = self._client_execution_thread_pool.submit(
+            _client_application.run, _client_application.Scenario.STREAM_STREAM,
+            self._fake_time_channel)
+        invocation_metadata, rpc = self._fake_time_channel.take_stream_stream(
+            _application_testing_common.FIRST_SERVICE_STRESTRE)
+        first_request = rpc.take_request()
+        rpc.send_response(_application_common.STREAM_STREAM_RESPONSE)
+        rpc.send_response(_application_common.STREAM_STREAM_RESPONSE)
+        second_request = rpc.take_request()
+        rpc.send_response(_application_common.STREAM_STREAM_RESPONSE)
+        rpc.send_response(_application_common.STREAM_STREAM_RESPONSE)
+        rpc.requests_closed()
+        rpc.terminate((), grpc.StatusCode.OK, '')
+        application_return_value = application_future.result()
+
+        self.assertEqual(_application_common.STREAM_STREAM_REQUEST,
+                         first_request)
+        self.assertEqual(_application_common.STREAM_STREAM_REQUEST,
+                         second_request)
+        self.assertIs(application_return_value.kind,
+                      _client_application.Outcome.Kind.SATISFACTORY)
+
+    def test_concurrent_stream_stream(self):
+        application_future = self._client_execution_thread_pool.submit(
+            _client_application.run,
+            _client_application.Scenario.CONCURRENT_STREAM_STREAM,
+            self._real_time_channel)
+        rpcs = []
+        for _ in range(test_constants.RPC_CONCURRENCY):
+            invocation_metadata, rpc = (
+                self._real_time_channel.take_stream_stream(
+                    _application_testing_common.FIRST_SERVICE_STRESTRE))
+            rpcs.append(rpc)
+        requests = {}
+        for rpc in rpcs:
+            requests[rpc] = [rpc.take_request()]
+        for rpc in rpcs:
+            rpc.send_response(_application_common.STREAM_STREAM_RESPONSE)
+            rpc.send_response(_application_common.STREAM_STREAM_RESPONSE)
+        for rpc in rpcs:
+            requests[rpc].append(rpc.take_request())
+        for rpc in rpcs:
+            rpc.send_response(_application_common.STREAM_STREAM_RESPONSE)
+            rpc.send_response(_application_common.STREAM_STREAM_RESPONSE)
+        for rpc in rpcs:
+            rpc.requests_closed()
+        for rpc in rpcs:
+            rpc.terminate((), grpc.StatusCode.OK, '')
+        application_return_value = application_future.result()
+
+        for requests_of_one_rpc in requests.values():
+            for request in requests_of_one_rpc:
+                self.assertEqual(_application_common.STREAM_STREAM_REQUEST,
+                                 request)
+        self.assertIs(application_return_value.kind,
+                      _client_application.Outcome.Kind.SATISFACTORY)
+
+    def test_cancelled_unary_unary(self):
+        application_future = self._client_execution_thread_pool.submit(
+            _client_application.run,
+            _client_application.Scenario.CANCEL_UNARY_UNARY,
+            self._fake_time_channel)
+        invocation_metadata, request, rpc = (
+            self._fake_time_channel.take_unary_unary(
+                _application_testing_common.FIRST_SERVICE_UNUN))
+        rpc.send_initial_metadata(())
+        rpc.cancelled()
+        application_return_value = application_future.result()
+
+        self.assertEqual(_application_common.UNARY_UNARY_REQUEST, request)
+        self.assertIs(application_return_value.kind,
+                      _client_application.Outcome.Kind.SATISFACTORY)
+
+    def test_status_stream_unary(self):
+        application_future = self._client_execution_thread_pool.submit(
+            _client_application.run,
+            _client_application.Scenario.CONCURRENT_STREAM_UNARY,
+            self._fake_time_channel)
+        rpcs = tuple(
+            self._fake_time_channel.take_stream_unary(
+                _application_testing_common.FIRST_SERVICE_STREUN)[1]
+            for _ in range(test_constants.THREAD_CONCURRENCY))
+        for rpc in rpcs:
+            rpc.take_request()
+            rpc.take_request()
+            rpc.take_request()
+            rpc.requests_closed()
+            rpc.send_initial_metadata((
+                ('my_metadata_key', 'My Metadata Value!',),))
+        for rpc in rpcs[:-1]:
+            rpc.terminate(_application_common.STREAM_UNARY_RESPONSE, (),
+                          grpc.StatusCode.OK, '')
+        rpcs[-1].terminate(_application_common.STREAM_UNARY_RESPONSE, (),
+                           grpc.StatusCode.RESOURCE_EXHAUSTED,
+                           'nope; not able to handle all those RPCs!')
+        application_return_value = application_future.result()
+
+        self.assertIs(application_return_value.kind,
+                      _client_application.Outcome.Kind.UNSATISFACTORY)
+
+    def test_status_stream_stream(self):
+        code = grpc.StatusCode.DEADLINE_EXCEEDED
+        details = 'test deadline exceeded!'
+
+        application_future = self._client_execution_thread_pool.submit(
+            _client_application.run, _client_application.Scenario.STREAM_STREAM,
+            self._real_time_channel)
+        invocation_metadata, rpc = self._real_time_channel.take_stream_stream(
+            _application_testing_common.FIRST_SERVICE_STRESTRE)
+        first_request = rpc.take_request()
+        rpc.send_response(_application_common.STREAM_STREAM_RESPONSE)
+        rpc.send_response(_application_common.STREAM_STREAM_RESPONSE)
+        second_request = rpc.take_request()
+        rpc.send_response(_application_common.STREAM_STREAM_RESPONSE)
+        rpc.send_response(_application_common.STREAM_STREAM_RESPONSE)
+        rpc.requests_closed()
+        rpc.terminate((), code, details)
+        application_return_value = application_future.result()
+
+        self.assertEqual(_application_common.STREAM_STREAM_REQUEST,
+                         first_request)
+        self.assertEqual(_application_common.STREAM_STREAM_REQUEST,
+                         second_request)
+        self.assertIs(application_return_value.kind,
+                      _client_application.Outcome.Kind.RPC_ERROR)
+        self.assertIs(application_return_value.code, code)
+        self.assertEqual(application_return_value.details, details)
+
+    def test_misbehaving_server_unary_unary(self):
+        application_future = self._client_execution_thread_pool.submit(
+            _client_application.run, _client_application.Scenario.UNARY_UNARY,
+            self._fake_time_channel)
+        invocation_metadata, request, rpc = (
+            self._fake_time_channel.take_unary_unary(
+                _application_testing_common.FIRST_SERVICE_UNUN))
+        rpc.send_initial_metadata(())
+        rpc.terminate(_application_common.ERRONEOUS_UNARY_UNARY_RESPONSE, (),
+                      grpc.StatusCode.OK, '')
+        application_return_value = application_future.result()
+
+        self.assertEqual(_application_common.UNARY_UNARY_REQUEST, request)
+        self.assertIs(application_return_value.kind,
+                      _client_application.Outcome.Kind.UNSATISFACTORY)
+
+    def test_misbehaving_server_stream_stream(self):
+        application_future = self._client_execution_thread_pool.submit(
+            _client_application.run, _client_application.Scenario.STREAM_STREAM,
+            self._real_time_channel)
+        invocation_metadata, rpc = self._real_time_channel.take_stream_stream(
+            _application_testing_common.FIRST_SERVICE_STRESTRE)
+        first_request = rpc.take_request()
+        rpc.send_response(_application_common.STREAM_STREAM_RESPONSE)
+        rpc.send_response(_application_common.STREAM_STREAM_RESPONSE)
+        rpc.send_response(_application_common.STREAM_STREAM_RESPONSE)
+        second_request = rpc.take_request()
+        rpc.send_response(_application_common.STREAM_STREAM_RESPONSE)
+        rpc.send_response(_application_common.STREAM_STREAM_RESPONSE)
+        rpc.send_response(_application_common.STREAM_STREAM_RESPONSE)
+        rpc.requests_closed()
+        rpc.terminate((), grpc.StatusCode.OK, '')
+        application_return_value = application_future.result()
+
+        self.assertEqual(_application_common.STREAM_STREAM_REQUEST,
+                         first_request)
+        self.assertEqual(_application_common.STREAM_STREAM_REQUEST,
+                         second_request)
+        self.assertIs(application_return_value.kind,
+                      _client_application.Outcome.Kind.UNSATISFACTORY)
+
+    def test_infinite_request_stream_real_time(self):
+        application_future = self._client_execution_thread_pool.submit(
+            _client_application.run,
+            _client_application.Scenario.INFINITE_REQUEST_STREAM,
+            self._real_time_channel)
+        invocation_metadata, rpc = self._real_time_channel.take_stream_unary(
+            _application_testing_common.FIRST_SERVICE_STREUN)
+        rpc.send_initial_metadata(())
+        first_request = rpc.take_request()
+        second_request = rpc.take_request()
+        third_request = rpc.take_request()
+        self._real_time.sleep_for(
+            _application_common.INFINITE_REQUEST_STREAM_TIMEOUT)
+        rpc.terminate(_application_common.STREAM_UNARY_RESPONSE, (),
+                      grpc.StatusCode.DEADLINE_EXCEEDED, '')
+        application_return_value = application_future.result()
+
+        self.assertEqual(_application_common.STREAM_UNARY_REQUEST,
+                         first_request)
+        self.assertEqual(_application_common.STREAM_UNARY_REQUEST,
+                         second_request)
+        self.assertEqual(_application_common.STREAM_UNARY_REQUEST,
+                         third_request)
+        self.assertIs(application_return_value.kind,
+                      _client_application.Outcome.Kind.SATISFACTORY)
+
+
+if __name__ == '__main__':
+    unittest.main(verbosity=2)
diff --git a/src/python/grpcio_tests/tests/testing/proto/__init__.py b/src/python/grpcio_tests/tests/testing/proto/__init__.py
new file mode 100644
index 0000000..1e12035
--- /dev/null
+++ b/src/python/grpcio_tests/tests/testing/proto/__init__.py
@@ -0,0 +1,13 @@
+# Copyright 2017 gRPC authors.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
diff --git a/src/python/grpcio_tests/tests/testing/proto/requests.proto b/src/python/grpcio_tests/tests/testing/proto/requests.proto
new file mode 100644
index 0000000..54a60bf
--- /dev/null
+++ b/src/python/grpcio_tests/tests/testing/proto/requests.proto
@@ -0,0 +1,29 @@
+// Copyright 2015 gRPC authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+syntax = "proto3";
+
+package tests_of_grpc_testing;
+
+message Up {
+  int32 first_up_field = 1;
+}
+
+message Charm {
+  int32 first_charm_field = 1;
+}
+
+message Top {
+  int32 first_top_field = 1;
+}
diff --git a/src/python/grpcio_tests/tests/testing/proto/services.proto b/src/python/grpcio_tests/tests/testing/proto/services.proto
new file mode 100644
index 0000000..cb15c0d
--- /dev/null
+++ b/src/python/grpcio_tests/tests/testing/proto/services.proto
@@ -0,0 +1,42 @@
+// Copyright 2017 gRPC authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+syntax = "proto3";
+
+import "tests/testing/proto/requests.proto";
+
+package tests_of_grpc_testing;
+
+message Down {
+  int32 first_down_field = 1;
+}
+
+message Strange {
+  int32 first_strange_field = 1;
+}
+
+message Bottom {
+  int32 first_bottom_field = 1;
+}
+
+service FirstService {
+  rpc UnUn(Up) returns (Down);
+  rpc UnStre(Charm) returns (stream Strange);
+  rpc StreUn(stream Charm) returns (Strange);
+  rpc StreStre(stream Top) returns (stream Bottom);
+}
+
+service SecondService {
+  rpc UnStre(Strange) returns (stream Charm);
+}
diff --git a/src/python/grpcio_tests/tests/tests.json b/src/python/grpcio_tests/tests/tests.json
index f86eeb7..c10719b 100644
--- a/src/python/grpcio_tests/tests/tests.json
+++ b/src/python/grpcio_tests/tests/tests.json
@@ -9,6 +9,7 @@
   "protoc_plugin._split_definitions_test.SplitSeparateTest",
   "protoc_plugin.beta_python_plugin_test.PythonPluginTest",
   "reflection._reflection_servicer_test.ReflectionServicerTest",
+  "testing._client_test.ClientTest",
   "testing._time_test.StrictFakeTimeTest",
   "testing._time_test.StrictRealTimeTest",
   "unit._api_test.AllTest",
diff --git a/src/ruby/ext/grpc/rb_call.c b/src/ruby/ext/grpc/rb_call.c
index b999548..74f189e 100644
--- a/src/ruby/ext/grpc/rb_call.c
+++ b/src/ruby/ext/grpc/rb_call.c
@@ -179,6 +179,38 @@
   return Qnil;
 }
 
+/* TODO: expose this as part of the surface API if needed.
+ * This is meant for internal usage by the "write thread" of grpc-ruby
+ * client-side bidi calls. It provides a way for the background write-thread
+ * to propogate failures to the main read-thread and give the user an error
+ * message. */
+static VALUE grpc_rb_call_cancel_with_status(VALUE self, VALUE status_code,
+                                             VALUE details) {
+  grpc_rb_call *call = NULL;
+  grpc_call_error err;
+  if (RTYPEDDATA_DATA(self) == NULL) {
+    // This call has been closed
+    return Qnil;
+  }
+
+  if (TYPE(details) != T_STRING || TYPE(status_code) != T_FIXNUM) {
+    rb_raise(rb_eTypeError,
+             "Bad parameter type error for cancel with status. Want Fixnum, "
+             "String.");
+    return Qnil;
+  }
+
+  TypedData_Get_Struct(self, grpc_rb_call, &grpc_call_data_type, call);
+  err = grpc_call_cancel_with_status(call->wrapped, NUM2LONG(status_code),
+                                     StringValueCStr(details), NULL);
+  if (err != GRPC_CALL_OK) {
+    rb_raise(grpc_rb_eCallError, "cancel with status failed: %s (code=%d)",
+             grpc_call_error_detail_of(err), err);
+  }
+
+  return Qnil;
+}
+
 /* Releases the c-level resources associated with a call
    Once a call has been closed, no further requests can be
    processed.
@@ -949,6 +981,8 @@
   /* Add ruby analogues of the Call methods. */
   rb_define_method(grpc_rb_cCall, "run_batch", grpc_rb_call_run_batch, 1);
   rb_define_method(grpc_rb_cCall, "cancel", grpc_rb_call_cancel, 0);
+  rb_define_method(grpc_rb_cCall, "cancel_with_status",
+                   grpc_rb_call_cancel_with_status, 2);
   rb_define_method(grpc_rb_cCall, "close", grpc_rb_call_close, 0);
   rb_define_method(grpc_rb_cCall, "peer", grpc_rb_call_get_peer, 0);
   rb_define_method(grpc_rb_cCall, "peer_cert", grpc_rb_call_get_peer_cert, 0);
diff --git a/src/ruby/lib/grpc/generic/bidi_call.rb b/src/ruby/lib/grpc/generic/bidi_call.rb
index 9e125cd..c2239d0 100644
--- a/src/ruby/lib/grpc/generic/bidi_call.rb
+++ b/src/ruby/lib/grpc/generic/bidi_call.rb
@@ -153,7 +153,12 @@
     rescue StandardError => e
       GRPC.logger.warn('bidi-write-loop: failed')
       GRPC.logger.warn(e)
-      raise e
+      if is_client
+        @call.cancel_with_status(GRPC::Core::StatusCodes::UNKNOWN,
+                                 "GRPC bidi call error: #{e.inspect}")
+      else
+        raise e
+      end
     ensure
       set_output_stream_done.call if is_client
     end
@@ -180,8 +185,8 @@
               batch_result = @call.run_batch(RECV_STATUS_ON_CLIENT => nil)
               @call.status = batch_result.status
               @call.trailing_metadata = @call.status.metadata if @call.status
-              batch_result.check_status
               GRPC.logger.debug("bidi-read-loop: done status #{@call.status}")
+              batch_result.check_status
             end
 
             GRPC.logger.debug('bidi-read-loop: done reading!')
diff --git a/src/ruby/spec/call_spec.rb b/src/ruby/spec/call_spec.rb
index 473ff4a..1cc0500 100644
--- a/src/ruby/spec/call_spec.rb
+++ b/src/ruby/spec/call_spec.rb
@@ -137,6 +137,39 @@
     end
   end
 
+  describe '#cancel' do
+    it 'completes ok' do
+      call = make_test_call
+      expect { call.cancel }.not_to raise_error
+    end
+
+    it 'completes ok when the call is closed' do
+      call = make_test_call
+      call.close
+      expect { call.cancel }.not_to raise_error
+    end
+  end
+
+  describe '#cancel_with_status' do
+    it 'completes ok' do
+      call = make_test_call
+      expect do
+        call.cancel_with_status(0, 'test status')
+      end.not_to raise_error
+      expect do
+        call.cancel_with_status(0, nil)
+      end.to raise_error(TypeError)
+    end
+
+    it 'completes ok when the call is closed' do
+      call = make_test_call
+      call.close
+      expect do
+        call.cancel_with_status(0, 'test status')
+      end.not_to raise_error
+    end
+  end
+
   def make_test_call
     @ch.create_call(nil, nil, 'dummy_method', nil, deadline)
   end
diff --git a/src/ruby/spec/client_server_spec.rb b/src/ruby/spec/client_server_spec.rb
index b48b417..1a9b47e 100644
--- a/src/ruby/spec/client_server_spec.rb
+++ b/src/ruby/spec/client_server_spec.rb
@@ -226,6 +226,62 @@
     svr_batch = server_call.run_batch(server_ops)
     expect(svr_batch.send_close).to be true
   end
+
+  def client_cancel_test(cancel_proc, expected_code,
+                         expected_details)
+    call = new_client_call
+    server_call = nil
+
+    server_thread = Thread.new do
+      server_call = server_allows_client_to_proceed
+    end
+
+    client_ops = {
+      CallOps::SEND_INITIAL_METADATA => {},
+      CallOps::RECV_INITIAL_METADATA => nil
+    }
+    batch_result = call.run_batch(client_ops)
+    expect(batch_result.send_metadata).to be true
+    expect(batch_result.metadata).to eq({})
+
+    cancel_proc.call(call)
+
+    server_thread.join
+    server_ops = {
+      CallOps::RECV_CLOSE_ON_SERVER => nil
+    }
+    svr_batch = server_call.run_batch(server_ops)
+    expect(svr_batch.send_close).to be true
+
+    client_ops = {
+      CallOps::RECV_STATUS_ON_CLIENT => {}
+    }
+    batch_result = call.run_batch(client_ops)
+
+    expect(batch_result.status.code).to be expected_code
+    expect(batch_result.status.details).to eq expected_details
+  end
+
+  it 'clients can cancel a call on the server' do
+    expected_code = StatusCodes::CANCELLED
+    expected_details = 'Cancelled'
+    cancel_proc = proc { |call| call.cancel }
+    client_cancel_test(cancel_proc, expected_code, expected_details)
+  end
+
+  it 'cancel_with_status unknown status' do
+    code = StatusCodes::UNKNOWN
+    details = 'test unknown reason'
+    cancel_proc = proc { |call| call.cancel_with_status(code, details) }
+    client_cancel_test(cancel_proc, code, details)
+  end
+
+  it 'cancel_with_status unknown status' do
+    code = StatusCodes::FAILED_PRECONDITION
+    details = 'test failed precondition reason'
+    cancel_proc = proc { |call| call.cancel_with_status(code, details) }
+    client_cancel_test(cancel_proc, code, details)
+  end
 end
 
 shared_examples 'GRPC metadata delivery works OK' do
diff --git a/src/ruby/spec/generic/client_stub_spec.rb b/src/ruby/spec/generic/client_stub_spec.rb
index e1e7a53..9539e56 100644
--- a/src/ruby/spec/generic/client_stub_spec.rb
+++ b/src/ruby/spec/generic/client_stub_spec.rb
@@ -472,7 +472,7 @@
         host = "localhost:#{server_port}"
         stub = GRPC::ClientStub.new(host, :this_channel_is_insecure)
         expect do
-          get_responses(stub)
+          get_responses(stub).collect { |r| r }
         end.to raise_error(ArgumentError,
                            /Header values must be of type string or array/)
       end
@@ -641,11 +641,101 @@
         expect(e.collect { |r| r }).to eq(@sent_msgs)
         th.join
       end
+
+      # Prompted by grpc/github #10526
+      describe 'surfacing of errors when sending requests' do
+        def run_server_bidi_send_one_then_read_indefinitely
+          @server.start
+          recvd_rpc = @server.request_call
+          recvd_call = recvd_rpc.call
+          server_call = GRPC::ActiveCall.new(
+            recvd_call, noop, noop, INFINITE_FUTURE,
+            metadata_received: true, started: false)
+          server_call.send_initial_metadata
+          server_call.remote_send('server response')
+          loop do
+            m = server_call.remote_read
+            break if m.nil?
+          end
+          # can't fail since initial metadata already sent
+          server_call.send_status(@pass, 'OK', true)
+        end
+
+        def verify_error_from_write_thread(stub, requests_to_push,
+                                           request_queue, expected_description)
+          # TODO: an improvement might be to raise the original exception from
+          # bidi call write loops instead of only cancelling the call
+          failing_marshal_proc = proc do |req|
+            fail req if req.is_a?(StandardError)
+            req
+          end
+          begin
+            e = get_responses(stub, marshal_proc: failing_marshal_proc)
+            first_response = e.next
+            expect(first_response).to eq('server response')
+            requests_to_push.each { |req| request_queue.push(req) }
+            e.collect { |r| r }
+          rescue GRPC::Unknown => e
+            exception = e
+          end
+          expect(exception.message.include?(expected_description)).to be(true)
+        end
+
+        # Provides an Enumerable view of a Queue
+        class BidiErrorTestingEnumerateForeverQueue
+          def initialize(queue)
+            @queue = queue
+          end
+
+          def each
+            loop do
+              msg = @queue.pop
+              yield msg
+            end
+          end
+        end
+
+        def run_error_in_client_request_stream_test(requests_to_push,
+                                                    expected_error_message)
+          # start a server that waits on a read indefinitely - it should
+          # see a cancellation and be able to break out
+          th = Thread.new { run_server_bidi_send_one_then_read_indefinitely }
+          stub = GRPC::ClientStub.new(@host, :this_channel_is_insecure)
+
+          request_queue = Queue.new
+          @sent_msgs = BidiErrorTestingEnumerateForeverQueue.new(request_queue)
+
+          verify_error_from_write_thread(stub,
+                                         requests_to_push,
+                                         request_queue,
+                                         expected_error_message)
+          # the write loop errror should cancel the call and end the
+          # server's request stream
+          th.join
+        end
+
+        it 'non-GRPC errors from the write loop surface when raised ' \
+          'at the start of a request stream' do
+          expected_error_message = 'expect error on first request'
+          requests_to_push = [StandardError.new(expected_error_message)]
+          run_error_in_client_request_stream_test(requests_to_push,
+                                                  expected_error_message)
+        end
+
+        it 'non-GRPC errors from the write loop surface when raised ' \
+          'during the middle of a request stream' do
+          expected_error_message = 'expect error on last request'
+          requests_to_push = %w( one two )
+          requests_to_push << StandardError.new(expected_error_message)
+          run_error_in_client_request_stream_test(requests_to_push,
+                                                  expected_error_message)
+        end
+      end
     end
 
     describe 'without a call operation' do
-      def get_responses(stub, deadline: nil)
-        e = stub.bidi_streamer(@method, @sent_msgs, noop, noop,
+      def get_responses(stub, deadline: nil, marshal_proc: noop)
+        e = stub.bidi_streamer(@method, @sent_msgs, marshal_proc, noop,
                                metadata: @metadata, deadline: deadline)
         expect(e).to be_a(Enumerator)
         e
@@ -658,8 +748,9 @@
       after(:each) do
         @op.wait # make sure wait doesn't hang
       end
-      def get_responses(stub, run_start_call_first: false, deadline: nil)
-        @op = stub.bidi_streamer(@method, @sent_msgs, noop, noop,
+      def get_responses(stub, run_start_call_first: false, deadline: nil,
+                        marshal_proc: noop)
+        @op = stub.bidi_streamer(@method, @sent_msgs, marshal_proc, noop,
                                  return_op: true,
                                  metadata: @metadata, deadline: deadline)
         expect(@op).to be_a(GRPC::ActiveCall::Operation)
diff --git a/src/ruby/spec/generic/rpc_server_spec.rb b/src/ruby/spec/generic/rpc_server_spec.rb
index e4fe594..b887eaa 100644
--- a/src/ruby/spec/generic/rpc_server_spec.rb
+++ b/src/ruby/spec/generic/rpc_server_spec.rb
@@ -178,6 +178,18 @@
 
 CheckCallAfterFinishedServiceStub = CheckCallAfterFinishedService.rpc_stub_class
 
+# A service with a bidi streaming method.
+class BidiService
+  include GRPC::GenericService
+  rpc :server_sends_bad_input, stream(EchoMsg), stream(EchoMsg)
+
+  def server_sends_bad_input(_, _)
+    'bad response. (not an enumerable, client sees an error)'
+  end
+end
+
+BidiStub = BidiService.rpc_stub_class
+
 describe GRPC::RpcServer do
   RpcServer = GRPC::RpcServer
   StatusCodes = GRPC::Core::StatusCodes
@@ -520,6 +532,29 @@
         t.join
         expect(one_failed_as_unavailable).to be(true)
       end
+
+      it 'should send a status UNKNOWN with a relevant message when the' \
+        'servers response stream is not an enumerable' do
+        @srv.handle(BidiService)
+        t = Thread.new { @srv.run }
+        @srv.wait_till_running
+        stub = BidiStub.new(@host, :this_channel_is_insecure, **client_opts)
+        responses = stub.server_sends_bad_input([])
+        exception = nil
+        begin
+          responses.each { |r| r }
+        rescue GRPC::Unknown => e
+          exception = e
+        end
+        # Erroneous responses sent from the server handler should cause an
+        # exception on the client with relevant info.
+        expected_details = 'NoMethodError: undefined method `each\' for '\
+          '"bad response. (not an enumerable, client sees an error)"'
+
+        expect(exception.inspect.include?(expected_details)).to be true
+        @srv.stop
+        t.join
+      end
     end
 
     context 'with connect metadata' do
diff --git a/test/core/client_channel/resolvers/dns_resolver_connectivity_test.c b/test/core/client_channel/resolvers/dns_resolver_connectivity_test.c
index 6e3d69c..364e180 100644
--- a/test/core/client_channel/resolvers/dns_resolver_connectivity_test.c
+++ b/test/core/client_channel/resolvers/dns_resolver_connectivity_test.c
@@ -60,7 +60,8 @@
 static grpc_ares_request *my_dns_lookup_ares(
     grpc_exec_ctx *exec_ctx, const char *dns_server, const char *addr,
     const char *default_port, grpc_pollset_set *interested_parties,
-    grpc_closure *on_done, grpc_lb_addresses **lb_addrs, bool check_grpclb) {
+    grpc_closure *on_done, grpc_lb_addresses **lb_addrs, bool check_grpclb,
+    char **service_config_json) {
   gpr_mu_lock(&g_mu);
   GPR_ASSERT(0 == strcmp("test", addr));
   grpc_error *error = GRPC_ERROR_NONE;
diff --git a/test/core/end2end/fuzzers/api_fuzzer.c b/test/core/end2end/fuzzers/api_fuzzer.c
index 01fa4f7..1228c9f 100644
--- a/test/core/end2end/fuzzers/api_fuzzer.c
+++ b/test/core/end2end/fuzzers/api_fuzzer.c
@@ -416,7 +416,8 @@
 grpc_ares_request *my_dns_lookup_ares(
     grpc_exec_ctx *exec_ctx, const char *dns_server, const char *addr,
     const char *default_port, grpc_pollset_set *interested_parties,
-    grpc_closure *on_done, grpc_lb_addresses **lb_addrs, bool check_grpclb) {
+    grpc_closure *on_done, grpc_lb_addresses **lb_addrs, bool check_grpclb,
+    char **service_config_json) {
   addr_req *r = gpr_malloc(sizeof(*r));
   r->addr = gpr_strdup(addr);
   r->on_done = on_done;
diff --git a/test/core/end2end/goaway_server_test.c b/test/core/end2end/goaway_server_test.c
index bf90e25..c3aca13 100644
--- a/test/core/end2end/goaway_server_test.c
+++ b/test/core/end2end/goaway_server_test.c
@@ -48,7 +48,8 @@
 static grpc_ares_request *(*iomgr_dns_lookup_ares)(
     grpc_exec_ctx *exec_ctx, const char *dns_server, const char *addr,
     const char *default_port, grpc_pollset_set *interested_parties,
-    grpc_closure *on_done, grpc_lb_addresses **addresses, bool check_grpclb);
+    grpc_closure *on_done, grpc_lb_addresses **addresses, bool check_grpclb,
+    char **service_config_json);
 
 static void set_resolve_port(int port) {
   gpr_mu_lock(&g_mu);
@@ -90,11 +91,12 @@
 static grpc_ares_request *my_dns_lookup_ares(
     grpc_exec_ctx *exec_ctx, const char *dns_server, const char *addr,
     const char *default_port, grpc_pollset_set *interested_parties,
-    grpc_closure *on_done, grpc_lb_addresses **lb_addrs, bool check_grpclb) {
+    grpc_closure *on_done, grpc_lb_addresses **lb_addrs, bool check_grpclb,
+    char **service_config_json) {
   if (0 != strcmp(addr, "test")) {
     return iomgr_dns_lookup_ares(exec_ctx, dns_server, addr, default_port,
                                  interested_parties, on_done, lb_addrs,
-                                 check_grpclb);
+                                 check_grpclb, service_config_json);
   }
 
   grpc_error *error = GRPC_ERROR_NONE;
diff --git a/test/core/surface/alarm_test.c b/test/core/surface/alarm_test.c
index baaa059..6971d92 100644
--- a/test/core/surface/alarm_test.c
+++ b/test/core/surface/alarm_test.c
@@ -73,6 +73,21 @@
     GPR_ASSERT(ev.success == 0);
     grpc_alarm_destroy(alarm);
   }
+  {
+    /* alarm_destroy before cq_next */
+    grpc_event ev;
+    void *tag = create_test_tag();
+    grpc_alarm *alarm =
+        grpc_alarm_create(cc, grpc_timeout_seconds_to_deadline(2), tag);
+
+    grpc_alarm_destroy(alarm);
+    ev = grpc_completion_queue_next(cc, grpc_timeout_seconds_to_deadline(1),
+                                    NULL);
+    GPR_ASSERT(ev.type == GRPC_OP_COMPLETE);
+    GPR_ASSERT(ev.tag == tag);
+    GPR_ASSERT(ev.success == 0);
+  }
+
   shutdown_and_destroy(cc);
 }
 
diff --git a/test/core/util/BUILD b/test/core/util/BUILD
index 9d899bc..1268c2c 100644
--- a/test/core/util/BUILD
+++ b/test/core/util/BUILD
@@ -38,7 +38,7 @@
 )
 
 grpc_cc_library(
-    name = "grpc_test_util",
+    name = "grpc_test_util_base",
     srcs = [
         "debugger_macros.c",
         "grpc_profiler.c",
@@ -68,11 +68,33 @@
     language = "C",
     deps = [
         ":gpr_test_util",
+        "//:grpc_common",
+    ],
+)
+
+grpc_cc_library(
+    name = "grpc_test_util",
+    srcs = [],
+    hdrs = [],
+    language = "C",
+    deps = [
+        ":grpc_test_util_base",
         "//:grpc",
     ],
 )
 
 grpc_cc_library(
+    name = "grpc_test_util_unsecure",
+    srcs = [],
+    hdrs = [],
+    language = "C",
+    deps = [
+        ":grpc_test_util_base",
+        "//:grpc_unsecure",
+    ],
+)
+
+grpc_cc_library(
     name = "one_corpus_entry_fuzzer",
     srcs = ["one_corpus_entry_fuzzer.c"],
     deps = [
diff --git a/test/core/util/port.c b/test/core/util/port.c
index f430c54..b1fc722 100644
--- a/test/core/util/port.c
+++ b/test/core/util/port.c
@@ -79,7 +79,7 @@
   chosen_ports[num_chosen_ports - 1] = port;
 }
 
-int grpc_pick_unused_port(void) {
+static int grpc_pick_unused_port_impl(void) {
   int port = grpc_pick_port_using_server();
   if (port != 0) {
     chose_port(port);
@@ -88,7 +88,7 @@
   return port;
 }
 
-int grpc_pick_unused_port_or_die(void) {
+static int grpc_pick_unused_port_or_die_impl(void) {
   int port = grpc_pick_unused_port();
   if (port == 0) {
     fprintf(stderr,
@@ -101,6 +101,31 @@
   return port;
 }
 
-void grpc_recycle_unused_port(int port) { GPR_ASSERT(free_chosen_port(port)); }
+static void grpc_recycle_unused_port_impl(int port) {
+  GPR_ASSERT(free_chosen_port(port));
+}
+
+static grpc_pick_port_functions g_pick_port_functions = {
+    grpc_pick_unused_port_impl, grpc_pick_unused_port_or_die_impl,
+    grpc_recycle_unused_port_impl};
+
+int grpc_pick_unused_port(void) {
+  return g_pick_port_functions.pick_unused_port_fn();
+}
+
+int grpc_pick_unused_port_or_die(void) {
+  return g_pick_port_functions.pick_unused_port_or_die_fn();
+}
+
+void grpc_recycle_unused_port(int port) {
+  g_pick_port_functions.recycle_unused_port_fn(port);
+}
+
+void grpc_set_pick_port_functions(grpc_pick_port_functions functions) {
+  GPR_ASSERT(functions.pick_unused_port_fn != NULL);
+  GPR_ASSERT(functions.pick_unused_port_or_die_fn != NULL);
+  GPR_ASSERT(functions.recycle_unused_port_fn != NULL);
+  g_pick_port_functions = functions;
+}
 
 #endif /* GRPC_TEST_PICK_PORT */
diff --git a/test/core/util/port.h b/test/core/util/port.h
index 154e8f8..602099d 100644
--- a/test/core/util/port.h
+++ b/test/core/util/port.h
@@ -23,6 +23,12 @@
 extern "C" {
 #endif
 
+typedef struct grpc_pick_port_functions {
+  int (*pick_unused_port_fn)(void);
+  int (*pick_unused_port_or_die_fn)(void);
+  void (*recycle_unused_port_fn)(int port);
+} grpc_pick_port_functions;
+
 /* pick a port number that is currently unused by either tcp or udp. return
    0 on failure. */
 int grpc_pick_unused_port(void);
@@ -36,6 +42,9 @@
  * ports back to the server if it is going to allocate a large number. */
 void grpc_recycle_unused_port(int port);
 
+/** Request the family of pick_port functions in \a functions be used. */
+void grpc_set_pick_port_functions(grpc_pick_port_functions functions);
+
 #ifdef __cplusplus
 }
 #endif
diff --git a/test/cpp/common/BUILD b/test/cpp/common/BUILD
index bd11733..be9c279 100644
--- a/test/cpp/common/BUILD
+++ b/test/cpp/common/BUILD
@@ -27,7 +27,7 @@
     name = "alarm_cpp_test",
     srcs = ["alarm_cpp_test.cc"],
     deps = [
-        "//:grpc++",
+        "//:grpc++_unsecure",
         "//test/core/util:gpr_test_util",
     ],
     external_deps = [
diff --git a/test/cpp/end2end/grpclb_end2end_test.cc b/test/cpp/end2end/grpclb_end2end_test.cc
index 4fef535..b5cff66 100644
--- a/test/cpp/end2end/grpclb_end2end_test.cc
+++ b/test/cpp/end2end/grpclb_end2end_test.cc
@@ -215,7 +215,8 @@
     {
       std::unique_lock<std::mutex> lock(mu_);
       if (shutdown_) goto done;
-      serverlist_cond_.wait(lock);
+      serverlist_cond_.wait(lock, [this] { return serverlist_ready_; });
+      serverlist_ready_ = false;
     }
 
     if (client_load_reporting_interval_seconds_ > 0) {
@@ -242,6 +243,7 @@
             .drop_token_counts[drop_token_count.load_balance_token()] +=
             drop_token_count.num_calls();
       }
+      load_report_ready_ = true;
       load_report_cond_.notify_one();
     }
   done:
@@ -285,12 +287,14 @@
 
   const ClientStats& WaitForLoadReport() {
     std::unique_lock<std::mutex> lock(mu_);
-    load_report_cond_.wait(lock);
+    load_report_cond_.wait(lock, [this] { return load_report_ready_; });
+    load_report_ready_ = false;
     return client_stats_;
   }
 
   void NotifyDoneWithServerlists() {
     std::lock_guard<std::mutex> lock(mu_);
+    serverlist_ready_ = true;
     serverlist_cond_.notify_one();
   }
 
@@ -313,7 +317,9 @@
   std::vector<ResponseDelayPair> responses_and_delays_;
   std::mutex mu_;
   std::condition_variable load_report_cond_;
+  bool load_report_ready_ = false;
   std::condition_variable serverlist_cond_;
+  bool serverlist_ready_ = false;
   ClientStats client_stats_;
   bool shutdown_;
 };
diff --git a/test/cpp/microbenchmarks/BUILD b/test/cpp/microbenchmarks/BUILD
index 5e1bcee..442da38 100644
--- a/test/cpp/microbenchmarks/BUILD
+++ b/test/cpp/microbenchmarks/BUILD
@@ -40,9 +40,9 @@
         "helpers.h",
     ],
     deps = [
-        "//:grpc++",
+        "//:grpc++_unsecure",
         "//src/proto/grpc/testing:echo_proto",
-        "//test/core/util:grpc_test_util",
+        "//test/core/util:grpc_test_util_unsecure",
     ],
     external_deps = [
         "benchmark",
diff --git a/test/cpp/qps/client_async.cc b/test/cpp/qps/client_async.cc
index f7dda0f..265f174 100644
--- a/test/cpp/qps/client_async.cc
+++ b/test/cpp/qps/client_async.cc
@@ -120,7 +120,7 @@
   BenchmarkService::Stub* stub_;
   CompletionQueue* cq_;
   std::unique_ptr<Alarm> alarm_;
-  RequestType req_;
+  const RequestType& req_;
   ResponseType response_;
   enum State { INVALID, READY, RESP_DONE };
   State next_state_;
@@ -415,7 +415,7 @@
   BenchmarkService::Stub* stub_;
   CompletionQueue* cq_;
   std::unique_ptr<Alarm> alarm_;
-  RequestType req_;
+  const RequestType& req_;
   ResponseType response_;
   enum State {
     INVALID,
@@ -554,7 +554,7 @@
   BenchmarkService::Stub* stub_;
   CompletionQueue* cq_;
   std::unique_ptr<Alarm> alarm_;
-  RequestType req_;
+  const RequestType& req_;
   ResponseType response_;
   enum State {
     INVALID,
@@ -672,7 +672,7 @@
   BenchmarkService::Stub* stub_;
   CompletionQueue* cq_;
   std::unique_ptr<Alarm> alarm_;
-  RequestType req_;
+  const RequestType& req_;
   ResponseType response_;
   enum State { INVALID, STREAM_IDLE, READ_DONE };
   State next_state_;
diff --git a/test/cpp/qps/server_async.cc b/test/cpp/qps/server_async.cc
index 122976c..8b00bcf 100644
--- a/test/cpp/qps/server_async.cc
+++ b/test/cpp/qps/server_async.cc
@@ -550,8 +550,7 @@
                                 ByteBuffer *response) {
   int resp_size = payload_config.bytebuf_params().resp_size();
   std::unique_ptr<char[]> buf(new char[resp_size]);
-  grpc_slice s = grpc_slice_from_copied_buffer(buf.get(), resp_size);
-  Slice slice(s, Slice::STEAL_REF);
+  Slice slice(buf.get(), resp_size);
   *response = ByteBuffer(&slice, 1);
   return Status::OK;
 }
diff --git a/test/cpp/server/BUILD b/test/cpp/server/BUILD
index 512241e..3f63be2 100644
--- a/test/cpp/server/BUILD
+++ b/test/cpp/server/BUILD
@@ -20,9 +20,9 @@
     name = "server_builder_test",
     srcs = ["server_builder_test.cc"],
     deps = [
-        "//:grpc++",
+        "//:grpc++_unsecure",
         "//src/proto/grpc/testing:echo_proto",
-        "//test/core/util:grpc_test_util",
+        "//test/core/util:grpc_test_util_unsecure",
     ],
     external_deps = [
         "gtest",
@@ -33,9 +33,9 @@
     name = "server_request_call_test",
     srcs = ["server_request_call_test.cc"],
     deps = [
-        "//:grpc++",
+        "//:grpc++_unsecure",
         "//src/proto/grpc/testing:echo_proto",
-        "//test/core/util:grpc_test_util",
+        "//test/core/util:grpc_test_util_unsecure",
     ],
     external_deps = [
         "gtest",
diff --git a/test/cpp/util/BUILD b/test/cpp/util/BUILD
index c9b0d6c..fbdec05 100644
--- a/test/cpp/util/BUILD
+++ b/test/cpp/util/BUILD
@@ -24,16 +24,6 @@
     ],
 )
 
-# The following builds a shared-object to confirm that grpc++_unsecure
-# builds properly. Build-only is sufficient here
-grpc_cc_binary(
-    name = "testso.so",
-    srcs = [],
-    linkshared = 1,
-    linkopts = ['-Wl,--no-undefined'],
-    deps = ["//:grpc++_unsecure"],
-)
-
 grpc_cc_library(
     name = "test_config",
     srcs = [
@@ -64,26 +54,43 @@
     ],
 )
 
+GRPCXX_TESTUTIL_SRCS  = [
+    "byte_buffer_proto_helper.cc",
+    "string_ref_helper.cc",
+    "subprocess.cc",
+]
+
+GRPCXX_TESTUTIL_HDRS = [
+    "byte_buffer_proto_helper.h",
+    "string_ref_helper.h",
+    "subprocess.h",
+]
+
 grpc_cc_library(
     name = "test_util",
-    srcs = [
-        "byte_buffer_proto_helper.cc",
+    srcs = GRPCXX_TESTUTIL_SRCS + [
         "create_test_channel.cc",
-        "string_ref_helper.cc",
-        "subprocess.cc",
         "test_credentials_provider.cc",
     ],
-    hdrs = [
-        "byte_buffer_proto_helper.h",
+    hdrs = GRPCXX_TESTUTIL_HDRS + [
         "create_test_channel.h",
-        "string_ref_helper.h",
-        "subprocess.h",
         "test_credentials_provider.h",
     ],
     deps = [
         "//:grpc++",
         "//test/core/end2end:ssl_test_data",
-        "//test/core/util:gpr_test_util",
+    ],
+    external_deps = [
+        "protobuf",
+    ],
+)
+
+grpc_cc_library(
+    name = "test_util_unsecure",
+    srcs = GRPCXX_TESTUTIL_SRCS,
+    hdrs = GRPCXX_TESTUTIL_HDRS,
+    deps = [
+        "//:grpc++_unsecure",
     ],
     external_deps = [
         "protobuf",
diff --git a/test/cpp/util/slice_test.cc b/test/cpp/util/slice_test.cc
index 9e3329f..8a8962d 100644
--- a/test/cpp/util/slice_test.cc
+++ b/test/cpp/util/slice_test.cc
@@ -63,6 +63,42 @@
   CheckSlice(spp, kContent);
 }
 
+TEST_F(SliceTest, SliceNew) {
+  char* x = new char[strlen(kContent) + 1];
+  strcpy(x, kContent);
+  Slice spp(x, strlen(x), [](void* p) { delete[] reinterpret_cast<char*>(p); });
+  CheckSlice(spp, kContent);
+}
+
+TEST_F(SliceTest, SliceNewDoNothing) {
+  Slice spp(const_cast<char*>(kContent), strlen(kContent), [](void* p) {});
+  CheckSlice(spp, kContent);
+}
+
+TEST_F(SliceTest, SliceNewWithUserData) {
+  struct stest {
+    char* x;
+    int y;
+  };
+  auto* t = new stest;
+  t->x = new char[strlen(kContent) + 1];
+  strcpy(t->x, kContent);
+  Slice spp(t->x, strlen(t->x),
+            [](void* p) {
+              auto* t = reinterpret_cast<stest*>(p);
+              delete[] t->x;
+              delete t;
+            },
+            t);
+  CheckSlice(spp, kContent);
+}
+
+TEST_F(SliceTest, SliceNewLen) {
+  Slice spp(const_cast<char*>(kContent), strlen(kContent),
+            [](void* p, size_t l) { EXPECT_EQ(l, strlen(kContent)); });
+  CheckSlice(spp, kContent);
+}
+
 TEST_F(SliceTest, Steal) {
   grpc_slice s = grpc_slice_from_copied_string(kContent);
   Slice spp(s, Slice::STEAL_REF);
diff --git a/tools/doxygen/Doxyfile.c++.internal b/tools/doxygen/Doxyfile.c++.internal
index 3352431..7290f20 100644
--- a/tools/doxygen/Doxyfile.c++.internal
+++ b/tools/doxygen/Doxyfile.c++.internal
@@ -959,6 +959,7 @@
 src/core/lib/iomgr/ev_posix.h \
 src/core/lib/iomgr/exec_ctx.h \
 src/core/lib/iomgr/executor.h \
+src/core/lib/iomgr/gethostname.h \
 src/core/lib/iomgr/iocp_windows.h \
 src/core/lib/iomgr/iomgr.h \
 src/core/lib/iomgr/iomgr_internal.h \
@@ -1033,6 +1034,7 @@
 src/core/lib/support/thd_internal.h \
 src/core/lib/support/time_precise.h \
 src/core/lib/support/tmpfile.h \
+src/core/lib/surface/alarm_internal.h \
 src/core/lib/surface/api_trace.h \
 src/core/lib/surface/call.h \
 src/core/lib/surface/call_test_only.h \
diff --git a/tools/doxygen/Doxyfile.core.internal b/tools/doxygen/Doxyfile.core.internal
index 9951edc..4901fc9 100644
--- a/tools/doxygen/Doxyfile.core.internal
+++ b/tools/doxygen/Doxyfile.core.internal
@@ -1116,6 +1116,10 @@
 src/core/lib/iomgr/exec_ctx.h \
 src/core/lib/iomgr/executor.c \
 src/core/lib/iomgr/executor.h \
+src/core/lib/iomgr/gethostname.h \
+src/core/lib/iomgr/gethostname_fallback.c \
+src/core/lib/iomgr/gethostname_host_name_max.c \
+src/core/lib/iomgr/gethostname_sysconf.c \
 src/core/lib/iomgr/iocp_windows.c \
 src/core/lib/iomgr/iocp_windows.h \
 src/core/lib/iomgr/iomgr.c \
@@ -1342,6 +1346,7 @@
 src/core/lib/support/wrap_memcpy.c \
 src/core/lib/surface/README.md \
 src/core/lib/surface/alarm.c \
+src/core/lib/surface/alarm_internal.h \
 src/core/lib/surface/api_trace.c \
 src/core/lib/surface/api_trace.h \
 src/core/lib/surface/byte_buffer.c \
@@ -1416,6 +1421,8 @@
 src/core/tsi/transport_security.h \
 src/core/tsi/transport_security_adapter.c \
 src/core/tsi/transport_security_adapter.h \
+src/core/tsi/transport_security_grpc.c \
+src/core/tsi/transport_security_grpc.h \
 src/core/tsi/transport_security_interface.h \
 third_party/nanopb/pb_common.c \
 third_party/nanopb/pb_decode.c \
diff --git a/tools/flakes/detect_flakes.py b/tools/flakes/detect_flakes.py
new file mode 100644
index 0000000..7c2f012
--- /dev/null
+++ b/tools/flakes/detect_flakes.py
@@ -0,0 +1,101 @@
+#!/usr/bin/env python
+# Copyright 2015 gRPC authors.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""Detect new flakes introduced in the last 24h hours with respect to the
+previous six days"""
+
+from __future__ import absolute_import
+from __future__ import division
+from __future__ import print_function
+
+import os
+import sys
+import logging
+logging.basicConfig(format='%(asctime)s %(message)s')
+
+gcp_utils_dir = os.path.abspath(
+    os.path.join(os.path.dirname(__file__), '../gcp/utils'))
+sys.path.append(gcp_utils_dir)
+
+import big_query_utils
+
+
+def get_flaky_tests(days_lower_bound, days_upper_bound, limit=None):
+  """ period is one of "WEEK", "DAY", etc.
+  (see https://cloud.google.com/bigquery/docs/reference/standard-sql/functions-and-operators#date_add). """
+
+  bq = big_query_utils.create_big_query()
+  query = """
+SELECT
+  filtered_test_name,
+  FIRST(timestamp),
+  FIRST(build_url),
+FROM (
+  SELECT
+    REGEXP_REPLACE(test_name, r'/\d+', '') AS filtered_test_name,
+    result,
+    build_url,
+    timestamp
+  FROM
+    [grpc-testing:jenkins_test_results.aggregate_results]
+  WHERE
+    timestamp >= DATE_ADD(CURRENT_DATE(), {days_lower_bound}, "DAY")
+    AND timestamp <= DATE_ADD(CURRENT_DATE(), {days_upper_bound}, "DAY")
+    AND NOT REGEXP_MATCH(job_name, '.*portability.*'))
+GROUP BY
+  filtered_test_name,
+  timestamp,
+  build_url
+HAVING
+  SUM(result != 'PASSED'
+    AND result != 'SKIPPED') > 0
+ORDER BY
+  timestamp ASC
+""".format(days_lower_bound=days_lower_bound, days_upper_bound=days_upper_bound)
+  if limit:
+    query += '\n LIMIT {}'.format(limit)
+  query_job = big_query_utils.sync_query_job(bq, 'grpc-testing', query)
+  page = bq.jobs().getQueryResults(
+      pageToken=None, **query_job['jobReference']).execute(num_retries=3)
+  testname_to_ts_url_pair = {row['f'][0]['v']: (row['f'][1]['v'], row['f'][2]['v']) for row in page['rows']}
+  return testname_to_ts_url_pair
+
+
+def get_new_flakes():
+  last_week_sans_yesterday = get_flaky_tests(-7, -1)
+  last_24 = get_flaky_tests(-1, +1)
+  last_week_sans_yesterday_names = set(last_week_sans_yesterday.keys())
+  last_24_names = set(last_24.keys())
+  logging.debug('|last_week_sans_yesterday| =', len(last_week_sans_yesterday_names))
+  logging.debug('|last_24_names| =', len(last_24_names))
+  new_flakes = last_24_names - last_week_sans_yesterday_names
+  logging.debug('|new_flakes| = ', len(new_flakes))
+  return {k: last_24[k] for k in new_flakes}
+
+
+def main():
+  import datetime
+  new_flakes = get_new_flakes()
+  if new_flakes:
+    print("Found {} new flakes:".format(len(new_flakes)))
+    for k, v in new_flakes.items():
+      ts = int(float(v[0]))
+      url = v[1]
+      human_ts = datetime.datetime.utcfromtimestamp(ts).strftime('%Y-%m-%d %H:%M:%S UTC')
+      print("Test: {}, Timestamp: {}, URL: {}\n".format(k, human_ts, url))
+
+
+if __name__ == '__main__':
+  main()
diff --git a/tools/internal_ci/helper_scripts/prepare_build_macos_interop_rc b/tools/internal_ci/helper_scripts/prepare_build_macos_interop_rc
new file mode 100644
index 0000000..f467ac0
--- /dev/null
+++ b/tools/internal_ci/helper_scripts/prepare_build_macos_interop_rc
@@ -0,0 +1,38 @@
+#!/bin/bash
+# Copyright 2017 gRPC authors.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+# Source this rc script to prepare the environment for MacOS interop
+# builds. This rc script must be used in the root directory of gRPC
+# and is expected to be used before prepare_build_macos_rc
+
+export CONFIG=opt
+
+# Move gRPC repo to directory that Docker for Mac has drive access to
+mkdir /Users/kbuilder/workspace
+cp -R ./ /Users/kbuilder/workspace/grpc
+cd /Users/kbuilder/workspace/grpc
+
+# Needed for identifying Docker image sha1
+brew install md5sha1sum
+
+# Set up gRPC-Go and gRPC-Java to test
+git clone --recursive https://github.com/grpc/grpc-go ./../grpc-go
+git clone --recursive https://github.com/grpc/grpc-java ./../grpc-java
+
+# Set up Docker for Mac
+docker-machine create -d virtualbox --virtualbox-share-folder "/Users/kbuilder/workspace:" default
+docker-machine env default
+eval $(docker-machine env default)
+
diff --git a/tools/internal_ci/helper_scripts/prepare_build_macos_rc b/tools/internal_ci/helper_scripts/prepare_build_macos_rc
index 00105d4..b48040f 100644
--- a/tools/internal_ci/helper_scripts/prepare_build_macos_rc
+++ b/tools/internal_ci/helper_scripts/prepare_build_macos_rc
@@ -31,7 +31,6 @@
 # pip does not install google-api-python-client properly, so use easy_install
 sudo easy_install --upgrade google-api-python-client
 export GOOGLE_APPLICATION_CREDENTIALS=${KOKORO_GFILE_DIR}/GrpcTesting-d0eeee2db331.json
-gcloud auth activate-service-account --key-file=$GOOGLE_APPLICATION_CREDENTIALS
 
 # required to build protobuf
 brew install gflags
diff --git a/tools/internal_ci/windows/grpc_portability_master.cfg b/tools/internal_ci/linux/grpc_build_boringssl_at_head.cfg
similarity index 80%
copy from tools/internal_ci/windows/grpc_portability_master.cfg
copy to tools/internal_ci/linux/grpc_build_boringssl_at_head.cfg
index c395cb4..11c211f 100644
--- a/tools/internal_ci/windows/grpc_portability_master.cfg
+++ b/tools/internal_ci/linux/grpc_build_boringssl_at_head.cfg
@@ -15,8 +15,8 @@
 # Config file for the internal CI (in protobuf text format)
 
 # Location of the continuous shell script in repository.
-build_file: "grpc/tools/internal_ci/windows/grpc_run_tests_matrix.bat"
-timeout_mins: 360
+build_file: "grpc/tools/internal_ci/linux/grpc_build_submodule_at_head.sh"
+timeout_mins: 180
 action {
   define_artifacts {
     regex: "**/*sponge_log.xml"
@@ -24,7 +24,8 @@
   }
 }
 
+# Tiny hack: misusing an already whitelisted env var to pass submodule name
 env_vars {
   key: "RUN_TESTS_FLAGS"
-  value: "-f portability windows -j 1 --inner_jobs 8 --internal_ci"
+  value: "boringssl"
 }
diff --git a/tools/internal_ci/windows/grpc_portability_master.cfg b/tools/internal_ci/linux/grpc_build_protobuf_at_head.cfg
similarity index 81%
copy from tools/internal_ci/windows/grpc_portability_master.cfg
copy to tools/internal_ci/linux/grpc_build_protobuf_at_head.cfg
index c395cb4..2f08e15 100644
--- a/tools/internal_ci/windows/grpc_portability_master.cfg
+++ b/tools/internal_ci/linux/grpc_build_protobuf_at_head.cfg
@@ -15,8 +15,8 @@
 # Config file for the internal CI (in protobuf text format)
 
 # Location of the continuous shell script in repository.
-build_file: "grpc/tools/internal_ci/windows/grpc_run_tests_matrix.bat"
-timeout_mins: 360
+build_file: "grpc/tools/internal_ci/linux/grpc_build_submodule_at_head.sh"
+timeout_mins: 180
 action {
   define_artifacts {
     regex: "**/*sponge_log.xml"
@@ -24,7 +24,8 @@
   }
 }
 
+# Tiny hack: misusing an already whitelisted env var to pass submodule name
 env_vars {
   key: "RUN_TESTS_FLAGS"
-  value: "-f portability windows -j 1 --inner_jobs 8 --internal_ci"
+  value: "protobuf"
 }
diff --git a/tools/internal_ci/linux/grpc_build_submodule_at_head.sh b/tools/internal_ci/linux/grpc_build_submodule_at_head.sh
new file mode 100755
index 0000000..8189e68
--- /dev/null
+++ b/tools/internal_ci/linux/grpc_build_submodule_at_head.sh
@@ -0,0 +1,30 @@
+#!/bin/bash
+# Copyright 2017 gRPC authors.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+# Build portability tests with an updated submodule
+
+set -ex
+
+# change to grpc repo root
+cd $(dirname $0)/../../..
+
+source tools/internal_ci/helper_scripts/prepare_build_linux_rc
+
+# Update submodule and commit it so changes are passed to Docker
+(cd third_party/$RUN_TESTS_FLAGS && git pull origin master)
+git -c user.name='foo' -c user.email='foo@google.com' commit -a -m 'Update submodule'
+
+tools/run_tests/run_tests_matrix.py -f linux --internal_ci --build_only
+
diff --git a/tools/internal_ci/macos/grpc_basictests.cfg b/tools/internal_ci/macos/grpc_basictests.cfg
deleted file mode 100644
index 3faba2f..0000000
--- a/tools/internal_ci/macos/grpc_basictests.cfg
+++ /dev/null
@@ -1,31 +0,0 @@
-# Copyright 2017 gRPC authors.
-#
-# Licensed under the Apache License, Version 2.0 (the "License");
-# you may not use this file except in compliance with the License.
-# You may obtain a copy of the License at
-#
-#     http://www.apache.org/licenses/LICENSE-2.0
-#
-# Unless required by applicable law or agreed to in writing, software
-# distributed under the License is distributed on an "AS IS" BASIS,
-# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-# See the License for the specific language governing permissions and
-# limitations under the License.
-
-# Config file for the internal CI (in protobuf text format)
-
-# Location of the continuous shell script in repository.
-build_file: "grpc/tools/internal_ci/macos/grpc_run_tests_matrix.sh"
-gfile_resources: "/bigstore/grpc-testing-secrets/gcp_credentials/GrpcTesting-d0eeee2db331.json"
-timeout_mins: 240
-action {
-  define_artifacts {
-    regex: "**/*sponge_log.xml"
-    regex: "github/grpc/reports/**"
-  }
-}
-
-env_vars {
-  key: "RUN_TESTS_FLAGS"
-  value: "-f basictests macos --internal_ci -j 1 --inner_jobs 4 --bq_result_table aggregate_results"
-}
diff --git a/tools/internal_ci/macos/grpc_interop.sh b/tools/internal_ci/macos/grpc_interop.sh
index 07601a6..b03401b 100755
--- a/tools/internal_ci/macos/grpc_interop.sh
+++ b/tools/internal_ci/macos/grpc_interop.sh
@@ -18,6 +18,7 @@
 # change to grpc repo root
 cd $(dirname $0)/../../..
 
-source tools/internal_ci/helper_scripts/prepare_build_interop_rc
+source tools/internal_ci/helper_scripts/prepare_build_macos_interop_rc
+source tools/internal_ci/helper_scripts/prepare_build_macos_rc
 
 tools/run_tests/run_interop_tests.py -l objc -s all --use_docker -t -j 1
diff --git a/tools/internal_ci/windows/grpc_portability_master.cfg b/tools/internal_ci/windows/grpc_portability_build_only.cfg
similarity index 92%
rename from tools/internal_ci/windows/grpc_portability_master.cfg
rename to tools/internal_ci/windows/grpc_portability_build_only.cfg
index c395cb4..b2b58ec 100644
--- a/tools/internal_ci/windows/grpc_portability_master.cfg
+++ b/tools/internal_ci/windows/grpc_portability_build_only.cfg
@@ -26,5 +26,5 @@
 
 env_vars {
   key: "RUN_TESTS_FLAGS"
-  value: "-f portability windows -j 1 --inner_jobs 8 --internal_ci"
+  value: "-f portability windows --internal_ci  --build_only"
 }
diff --git a/tools/run_tests/dockerize/build_interop_stress_image.sh b/tools/run_tests/dockerize/build_interop_stress_image.sh
deleted file mode 100755
index acb566f..0000000
--- a/tools/run_tests/dockerize/build_interop_stress_image.sh
+++ /dev/null
@@ -1,93 +0,0 @@
-#!/bin/bash
-# Copyright 2015 gRPC authors.
-#
-# Licensed under the Apache License, Version 2.0 (the "License");
-# you may not use this file except in compliance with the License.
-# You may obtain a copy of the License at
-#
-#     http://www.apache.org/licenses/LICENSE-2.0
-#
-# Unless required by applicable law or agreed to in writing, software
-# distributed under the License is distributed on an "AS IS" BASIS,
-# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-# See the License for the specific language governing permissions and
-# limitations under the License.
-#
-# This script is invoked by run_interop_tests.py to build the docker image
-# for interop testing. You should never need to call this script on your own.
-
-set -x
-
-# Params:
-#  INTEROP_IMAGE - Name of tag of the final interop image
-#  INTEROP_IMAGE_REPOSITORY_TAG - Optional. If set, the created image will be tagged using
-#    the command: 'docker tag $INTEROP_IMAGE $INTEROP_IMAGE_REPOSITORY_TAG'
-#  BASE_NAME - Base name used to locate the base Dockerfile and build script
-#  BUILD_TYPE - The 'CONFIG' variable passed to the 'make' command (example:
-#  asan, tsan. Default value: opt).
-#  TTY_FLAG - optional -t flag to make docker allocate tty
-#  BUILD_INTEROP_DOCKER_EXTRA_ARGS - optional args to be passed to the
-#    docker run command
-
-cd `dirname $0`/../../..
-GRPC_ROOT=`pwd`
-MOUNT_ARGS="-v $GRPC_ROOT:/var/local/jenkins/grpc:ro"
-
-GRPC_JAVA_ROOT=`cd ../grpc-java && pwd`
-if [ "$GRPC_JAVA_ROOT" != "" ]
-then
-  MOUNT_ARGS+=" -v $GRPC_JAVA_ROOT:/var/local/jenkins/grpc-java:ro"
-else
-  echo "WARNING: grpc-java not found, it won't be mounted to the docker container."
-fi
-
-GRPC_GO_ROOT=`cd ../grpc-go && pwd`
-if [ "$GRPC_GO_ROOT" != "" ]
-then
-  MOUNT_ARGS+=" -v $GRPC_GO_ROOT:/var/local/jenkins/grpc-go:ro"
-else
-  echo "WARNING: grpc-go not found, it won't be mounted to the docker container."
-fi
-
-mkdir -p /tmp/ccache
-
-# Mount service account dir if available.
-# If service_directory does not contain the service account JSON file,
-# some of the tests will fail.
-if [ -e $HOME/service_account ]
-then
-  MOUNT_ARGS+=" -v $HOME/service_account:/var/local/jenkins/service_account:ro"
-fi
-
-# Use image name based on Dockerfile checksum
-BASE_IMAGE=${BASE_NAME}_base:`sha1sum tools/dockerfile/stress_test/$BASE_NAME/Dockerfile | cut -f1 -d\ `
-
-# Make sure base docker image has been built. Should be instantaneous if so.
-docker build -t $BASE_IMAGE --force-rm=true tools/dockerfile/stress_test/$BASE_NAME || exit $?
-
-# Create a local branch so the child Docker script won't complain
-git branch -f jenkins-docker
-
-CONTAINER_NAME="build_${BASE_NAME}_$(uuidgen)"
-
-# Prepare image for interop tests, commit it on success.
-(docker run \
-  -e CCACHE_DIR=/tmp/ccache \
-  -e THIS_IS_REALLY_NEEDED='see https://github.com/docker/docker/issues/14203 for why docker is awful' \
-  -e BUILD_TYPE=${BUILD_TYPE:=opt} \
-  -i $TTY_FLAG \
-  $MOUNT_ARGS \
-  $BUILD_INTEROP_DOCKER_EXTRA_ARGS \
-  -v /tmp/ccache:/tmp/ccache \
-  --name=$CONTAINER_NAME \
-  $BASE_IMAGE \
-  bash -l /var/local/jenkins/grpc/tools/dockerfile/stress_test/$BASE_NAME/build_interop_stress.sh \
-  && docker commit $CONTAINER_NAME $INTEROP_IMAGE \
-  && ( if [ -n "$INTEROP_IMAGE_REPOSITORY_TAG" ]; then docker tag $INTEROP_IMAGE $INTEROP_IMAGE_REPOSITORY_TAG ; fi ) \
-  && echo "Successfully built image $INTEROP_IMAGE")
-EXITCODE=$?
-
-# remove intermediate container, possibly killing it first
-docker rm -f $CONTAINER_NAME
-
-exit $EXITCODE
diff --git a/tools/run_tests/generated/sources_and_headers.json b/tools/run_tests/generated/sources_and_headers.json
index d5eba6e..30fef6f 100644
--- a/tools/run_tests/generated/sources_and_headers.json
+++ b/tools/run_tests/generated/sources_and_headers.json
@@ -7833,6 +7833,9 @@
       "src/core/lib/iomgr/ev_windows.c", 
       "src/core/lib/iomgr/exec_ctx.c", 
       "src/core/lib/iomgr/executor.c", 
+      "src/core/lib/iomgr/gethostname_fallback.c", 
+      "src/core/lib/iomgr/gethostname_host_name_max.c", 
+      "src/core/lib/iomgr/gethostname_sysconf.c", 
       "src/core/lib/iomgr/iocp_windows.c", 
       "src/core/lib/iomgr/iomgr.c", 
       "src/core/lib/iomgr/iomgr_posix.c", 
@@ -7979,6 +7982,7 @@
       "src/core/lib/iomgr/ev_posix.h", 
       "src/core/lib/iomgr/exec_ctx.h", 
       "src/core/lib/iomgr/executor.h", 
+      "src/core/lib/iomgr/gethostname.h", 
       "src/core/lib/iomgr/iocp_windows.h", 
       "src/core/lib/iomgr/iomgr.h", 
       "src/core/lib/iomgr/iomgr_internal.h", 
@@ -8035,6 +8039,7 @@
       "src/core/lib/slice/slice_hash_table.h", 
       "src/core/lib/slice/slice_internal.h", 
       "src/core/lib/slice/slice_string_helpers.h", 
+      "src/core/lib/surface/alarm_internal.h", 
       "src/core/lib/surface/api_trace.h", 
       "src/core/lib/surface/call.h", 
       "src/core/lib/surface/call_test_only.h", 
@@ -8107,6 +8112,7 @@
       "src/core/lib/iomgr/ev_posix.h", 
       "src/core/lib/iomgr/exec_ctx.h", 
       "src/core/lib/iomgr/executor.h", 
+      "src/core/lib/iomgr/gethostname.h", 
       "src/core/lib/iomgr/iocp_windows.h", 
       "src/core/lib/iomgr/iomgr.h", 
       "src/core/lib/iomgr/iomgr_internal.h", 
@@ -8163,6 +8169,7 @@
       "src/core/lib/slice/slice_hash_table.h", 
       "src/core/lib/slice/slice_internal.h", 
       "src/core/lib/slice/slice_string_helpers.h", 
+      "src/core/lib/surface/alarm_internal.h", 
       "src/core/lib/surface/api_trace.h", 
       "src/core/lib/surface/call.h", 
       "src/core/lib/surface/call_test_only.h", 
@@ -9088,16 +9095,15 @@
     "deps": [
       "gpr", 
       "grpc_base", 
-      "grpc_trace"
+      "grpc_trace", 
+      "tsi_interface"
     ], 
     "headers": [
       "src/core/tsi/fake_transport_security.h", 
       "src/core/tsi/gts_transport_security.h", 
       "src/core/tsi/ssl_transport_security.h", 
       "src/core/tsi/ssl_types.h", 
-      "src/core/tsi/transport_security.h", 
-      "src/core/tsi/transport_security_adapter.h", 
-      "src/core/tsi/transport_security_interface.h"
+      "src/core/tsi/transport_security_grpc.h"
     ], 
     "is_filegroup": true, 
     "language": "c", 
@@ -9110,6 +9116,26 @@
       "src/core/tsi/ssl_transport_security.c", 
       "src/core/tsi/ssl_transport_security.h", 
       "src/core/tsi/ssl_types.h", 
+      "src/core/tsi/transport_security_grpc.c", 
+      "src/core/tsi/transport_security_grpc.h"
+    ], 
+    "third_party": false, 
+    "type": "filegroup"
+  }, 
+  {
+    "deps": [
+      "gpr", 
+      "grpc_trace"
+    ], 
+    "headers": [
+      "src/core/tsi/transport_security.h", 
+      "src/core/tsi/transport_security_adapter.h", 
+      "src/core/tsi/transport_security_interface.h"
+    ], 
+    "is_filegroup": true, 
+    "language": "c", 
+    "name": "tsi_interface", 
+    "src": [
       "src/core/tsi/transport_security.c", 
       "src/core/tsi/transport_security.h", 
       "src/core/tsi/transport_security_adapter.c", 
diff --git a/tools/run_tests/run_build_statistics.py b/tools/run_tests/run_build_statistics.py
index d63dc3e..0ac6fc5 100755
--- a/tools/run_tests/run_build_statistics.py
+++ b/tools/run_tests/run_build_statistics.py
@@ -152,16 +152,13 @@
     failure_count = test_result['failCount']
     build_result['pass_count'] = test_result['passCount']
     build_result['failure_count'] = failure_count
+    # This means Jenkins failure occurred.
     build_result['no_report_files_found'] = _no_report_files_found(html)
-    if failure_count > 0:
+    # Only check errors if Jenkins failure occurred.
+    if build_result['no_report_files_found']:
       error_list, known_error_count = _scrape_for_known_errors(html)
-      unknown_error_count = failure_count - known_error_count
-      # This can happen if the same error occurs multiple times in one test.
-      if failure_count < known_error_count:
-        print('====> Some errors are duplicates.')
-        unknown_error_count = 0
-      error_list.append({'description': _UNKNOWN_ERROR, 
-                         'count': unknown_error_count})
+      if not error_list:
+        error_list.append({'description': _UNKNOWN_ERROR, 'count': 1})
   except Exception as e:
     print('====> Got exception for %s: %s.' % (json_url, str(e)))   
     print('====> Parsing errors from %s.' % console_url)
@@ -176,6 +173,8 @@
  
   if error_list:
     build_result['error'] = error_list
+  else:
+    build_result['error'] = [{'description': '', 'count': 0}]
 
   return build_result 
 
diff --git a/tools/run_tests/run_interop_tests.py b/tools/run_tests/run_interop_tests.py
index dbbf2ad..1537641 100755
--- a/tools/run_tests/run_interop_tests.py
+++ b/tools/run_tests/run_interop_tests.py
@@ -731,7 +731,7 @@
     if manual_cmd_log is not None:
       if manual_cmd_log == []:
         manual_cmd_log.append('echo "Testing ${docker_image:=%s}"' % docker_image)
-      manual_cmd_log.append(manual_cmdline(cmdline, docker_iamge))
+      manual_cmd_log.append(manual_cmdline(cmdline, docker_image))
     cwd = None
 
   test_job = jobset.JobSpec(
@@ -793,7 +793,7 @@
   if manual_cmd_log is not None:
       if manual_cmd_log == []:
         manual_cmd_log.append('echo "Testing ${docker_image:=%s}"' % docker_image)
-      manual_cmd_log.append(manual_cmdline(docker_cmdline, docker_iamge))
+      manual_cmd_log.append(manual_cmdline(docker_cmdline, docker_image))
   server_job = jobset.JobSpec(
           cmdline=docker_cmdline,
           environ=environ,
diff --git a/tools/run_tests/run_tests.py b/tools/run_tests/run_tests.py
index c953f90..461928b 100755
--- a/tools/run_tests/run_tests.py
+++ b/tools/run_tests/run_tests.py
@@ -74,19 +74,21 @@
 
   bq = big_query_utils.create_big_query()
   query = """
-    SELECT
-      test_name,
-      SUM(result != 'PASSED'
-        AND result != 'SKIPPED') AS count_failed,
-    FROM
-      [grpc-testing:jenkins_test_results.aggregate_results]
-    WHERE
-      timestamp >= DATE_ADD(CURRENT_DATE(), -1, "WEEK")
-      AND NOT REGEXP_MATCH(job_name, '.*portability.*')
-    GROUP BY
-      test_name
-    HAVING
-      count_failed > 0"""
+SELECT
+  filtered_test_name,
+  FROM (
+  SELECT
+    REGEXP_REPLACE(test_name, r'/\d+', '') AS filtered_test_name,
+    result
+  FROM
+    [grpc-testing:jenkins_test_results.aggregate_results]
+  WHERE
+    timestamp >= DATE_ADD(CURRENT_DATE(), -1, "WEEK")
+    AND NOT REGEXP_MATCH(job_name, '.*portability.*') )
+GROUP BY
+  filtered_test_name
+HAVING
+  SUM(result != 'PASSED' AND result != 'SKIPPED') > 0"""
   if limit:
     query += " limit {}".format(limit)
   query_job = big_query_utils.sync_query_job(bq, 'grpc-testing', query)
diff --git a/tools/run_tests/sanity/core_untyped_structs.sh b/tools/run_tests/sanity/core_untyped_structs.sh
new file mode 100755
index 0000000..792dd68
--- /dev/null
+++ b/tools/run_tests/sanity/core_untyped_structs.sh
@@ -0,0 +1,27 @@
+#!/bin/sh
+# Copyright 2017 gRPC authors.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+set -e
+
+cd `dirname $0`/../../..
+
+#
+# Make sure that all core struct/unions have a name or are typedef'ed
+#
+
+egrep -Irn '(struct|union) *{' include/grpc |
+    egrep -v typedef |
+    diff - /dev/null
+
diff --git a/tools/run_tests/sanity/sanity_tests.yaml b/tools/run_tests/sanity/sanity_tests.yaml
index a86ebee..7e582bc 100644
--- a/tools/run_tests/sanity/sanity_tests.yaml
+++ b/tools/run_tests/sanity/sanity_tests.yaml
@@ -6,6 +6,7 @@
 - script: tools/run_tests/sanity/check_test_filtering.py
 - script: tools/run_tests/sanity/check_tracer_sanity.py
 - script: tools/run_tests/sanity/core_banned_functions.py
+- script: tools/run_tests/sanity/core_untyped_structs.sh
 - script: tools/buildgen/generate_projects.sh -j 3
   cpu_cost: 3
 - script: tools/distrib/check_copyright.py
diff --git a/vsprojects/vcxproj/grpc++/grpc++.vcxproj b/vsprojects/vcxproj/grpc++/grpc++.vcxproj
index 625c62a..416adb4 100644
--- a/vsprojects/vcxproj/grpc++/grpc++.vcxproj
+++ b/vsprojects/vcxproj/grpc++/grpc++.vcxproj
@@ -450,6 +450,7 @@
     <ClInclude Include="$(SolutionDir)\..\src\core\lib\iomgr\ev_posix.h" />
     <ClInclude Include="$(SolutionDir)\..\src\core\lib\iomgr\exec_ctx.h" />
     <ClInclude Include="$(SolutionDir)\..\src\core\lib\iomgr\executor.h" />
+    <ClInclude Include="$(SolutionDir)\..\src\core\lib\iomgr\gethostname.h" />
     <ClInclude Include="$(SolutionDir)\..\src\core\lib\iomgr\iocp_windows.h" />
     <ClInclude Include="$(SolutionDir)\..\src\core\lib\iomgr\iomgr.h" />
     <ClInclude Include="$(SolutionDir)\..\src\core\lib\iomgr\iomgr_internal.h" />
@@ -506,6 +507,7 @@
     <ClInclude Include="$(SolutionDir)\..\src\core\lib\slice\slice_hash_table.h" />
     <ClInclude Include="$(SolutionDir)\..\src\core\lib\slice\slice_internal.h" />
     <ClInclude Include="$(SolutionDir)\..\src\core\lib\slice\slice_string_helpers.h" />
+    <ClInclude Include="$(SolutionDir)\..\src\core\lib\surface\alarm_internal.h" />
     <ClInclude Include="$(SolutionDir)\..\src\core\lib\surface\api_trace.h" />
     <ClInclude Include="$(SolutionDir)\..\src\core\lib\surface\call.h" />
     <ClInclude Include="$(SolutionDir)\..\src\core\lib\surface\call_test_only.h" />
diff --git a/vsprojects/vcxproj/grpc++/grpc++.vcxproj.filters b/vsprojects/vcxproj/grpc++/grpc++.vcxproj.filters
index ff9913a..0e33351 100644
--- a/vsprojects/vcxproj/grpc++/grpc++.vcxproj.filters
+++ b/vsprojects/vcxproj/grpc++/grpc++.vcxproj.filters
@@ -701,6 +701,9 @@
     <ClInclude Include="$(SolutionDir)\..\src\core\lib\iomgr\executor.h">
       <Filter>src\core\lib\iomgr</Filter>
     </ClInclude>
+    <ClInclude Include="$(SolutionDir)\..\src\core\lib\iomgr\gethostname.h">
+      <Filter>src\core\lib\iomgr</Filter>
+    </ClInclude>
     <ClInclude Include="$(SolutionDir)\..\src\core\lib\iomgr\iocp_windows.h">
       <Filter>src\core\lib\iomgr</Filter>
     </ClInclude>
@@ -869,6 +872,9 @@
     <ClInclude Include="$(SolutionDir)\..\src\core\lib\slice\slice_string_helpers.h">
       <Filter>src\core\lib\slice</Filter>
     </ClInclude>
+    <ClInclude Include="$(SolutionDir)\..\src\core\lib\surface\alarm_internal.h">
+      <Filter>src\core\lib\surface</Filter>
+    </ClInclude>
     <ClInclude Include="$(SolutionDir)\..\src\core\lib\surface\api_trace.h">
       <Filter>src\core\lib\surface</Filter>
     </ClInclude>
diff --git a/vsprojects/vcxproj/grpc++_unsecure/grpc++_unsecure.vcxproj b/vsprojects/vcxproj/grpc++_unsecure/grpc++_unsecure.vcxproj
index baeb6e3..8ea35c1 100644
--- a/vsprojects/vcxproj/grpc++_unsecure/grpc++_unsecure.vcxproj
+++ b/vsprojects/vcxproj/grpc++_unsecure/grpc++_unsecure.vcxproj
@@ -444,6 +444,7 @@
     <ClInclude Include="$(SolutionDir)\..\src\core\lib\iomgr\ev_posix.h" />
     <ClInclude Include="$(SolutionDir)\..\src\core\lib\iomgr\exec_ctx.h" />
     <ClInclude Include="$(SolutionDir)\..\src\core\lib\iomgr\executor.h" />
+    <ClInclude Include="$(SolutionDir)\..\src\core\lib\iomgr\gethostname.h" />
     <ClInclude Include="$(SolutionDir)\..\src\core\lib\iomgr\iocp_windows.h" />
     <ClInclude Include="$(SolutionDir)\..\src\core\lib\iomgr\iomgr.h" />
     <ClInclude Include="$(SolutionDir)\..\src\core\lib\iomgr\iomgr_internal.h" />
@@ -500,6 +501,7 @@
     <ClInclude Include="$(SolutionDir)\..\src\core\lib\slice\slice_hash_table.h" />
     <ClInclude Include="$(SolutionDir)\..\src\core\lib\slice\slice_internal.h" />
     <ClInclude Include="$(SolutionDir)\..\src\core\lib\slice\slice_string_helpers.h" />
+    <ClInclude Include="$(SolutionDir)\..\src\core\lib\surface\alarm_internal.h" />
     <ClInclude Include="$(SolutionDir)\..\src\core\lib\surface\api_trace.h" />
     <ClInclude Include="$(SolutionDir)\..\src\core\lib\surface\call.h" />
     <ClInclude Include="$(SolutionDir)\..\src\core\lib\surface\call_test_only.h" />
diff --git a/vsprojects/vcxproj/grpc++_unsecure/grpc++_unsecure.vcxproj.filters b/vsprojects/vcxproj/grpc++_unsecure/grpc++_unsecure.vcxproj.filters
index 5820ce0..edc3b81 100644
--- a/vsprojects/vcxproj/grpc++_unsecure/grpc++_unsecure.vcxproj.filters
+++ b/vsprojects/vcxproj/grpc++_unsecure/grpc++_unsecure.vcxproj.filters
@@ -668,6 +668,9 @@
     <ClInclude Include="$(SolutionDir)\..\src\core\lib\iomgr\executor.h">
       <Filter>src\core\lib\iomgr</Filter>
     </ClInclude>
+    <ClInclude Include="$(SolutionDir)\..\src\core\lib\iomgr\gethostname.h">
+      <Filter>src\core\lib\iomgr</Filter>
+    </ClInclude>
     <ClInclude Include="$(SolutionDir)\..\src\core\lib\iomgr\iocp_windows.h">
       <Filter>src\core\lib\iomgr</Filter>
     </ClInclude>
@@ -836,6 +839,9 @@
     <ClInclude Include="$(SolutionDir)\..\src\core\lib\slice\slice_string_helpers.h">
       <Filter>src\core\lib\slice</Filter>
     </ClInclude>
+    <ClInclude Include="$(SolutionDir)\..\src\core\lib\surface\alarm_internal.h">
+      <Filter>src\core\lib\surface</Filter>
+    </ClInclude>
     <ClInclude Include="$(SolutionDir)\..\src\core\lib\surface\api_trace.h">
       <Filter>src\core\lib\surface</Filter>
     </ClInclude>
diff --git a/vsprojects/vcxproj/grpc/grpc.vcxproj b/vsprojects/vcxproj/grpc/grpc.vcxproj
index 3f711f6..8a65928 100644
--- a/vsprojects/vcxproj/grpc/grpc.vcxproj
+++ b/vsprojects/vcxproj/grpc/grpc.vcxproj
@@ -347,6 +347,7 @@
     <ClInclude Include="$(SolutionDir)\..\src\core\tsi\gts_transport_security.h" />
     <ClInclude Include="$(SolutionDir)\..\src\core\tsi\ssl_transport_security.h" />
     <ClInclude Include="$(SolutionDir)\..\src\core\tsi\ssl_types.h" />
+    <ClInclude Include="$(SolutionDir)\..\src\core\tsi\transport_security_grpc.h" />
     <ClInclude Include="$(SolutionDir)\..\src\core\tsi\transport_security.h" />
     <ClInclude Include="$(SolutionDir)\..\src\core\tsi\transport_security_adapter.h" />
     <ClInclude Include="$(SolutionDir)\..\src\core\tsi\transport_security_interface.h" />
@@ -401,6 +402,7 @@
     <ClInclude Include="$(SolutionDir)\..\src\core\lib\iomgr\ev_posix.h" />
     <ClInclude Include="$(SolutionDir)\..\src\core\lib\iomgr\exec_ctx.h" />
     <ClInclude Include="$(SolutionDir)\..\src\core\lib\iomgr\executor.h" />
+    <ClInclude Include="$(SolutionDir)\..\src\core\lib\iomgr\gethostname.h" />
     <ClInclude Include="$(SolutionDir)\..\src\core\lib\iomgr\iocp_windows.h" />
     <ClInclude Include="$(SolutionDir)\..\src\core\lib\iomgr\iomgr.h" />
     <ClInclude Include="$(SolutionDir)\..\src\core\lib\iomgr\iomgr_internal.h" />
@@ -457,6 +459,7 @@
     <ClInclude Include="$(SolutionDir)\..\src\core\lib\slice\slice_hash_table.h" />
     <ClInclude Include="$(SolutionDir)\..\src\core\lib\slice\slice_internal.h" />
     <ClInclude Include="$(SolutionDir)\..\src\core\lib\slice\slice_string_helpers.h" />
+    <ClInclude Include="$(SolutionDir)\..\src\core\lib\surface\alarm_internal.h" />
     <ClInclude Include="$(SolutionDir)\..\src\core\lib\surface\api_trace.h" />
     <ClInclude Include="$(SolutionDir)\..\src\core\lib\surface\call.h" />
     <ClInclude Include="$(SolutionDir)\..\src\core\lib\surface\call_test_only.h" />
@@ -582,6 +585,12 @@
     </ClCompile>
     <ClCompile Include="$(SolutionDir)\..\src\core\lib\iomgr\executor.c">
     </ClCompile>
+    <ClCompile Include="$(SolutionDir)\..\src\core\lib\iomgr\gethostname_fallback.c">
+    </ClCompile>
+    <ClCompile Include="$(SolutionDir)\..\src\core\lib\iomgr\gethostname_host_name_max.c">
+    </ClCompile>
+    <ClCompile Include="$(SolutionDir)\..\src\core\lib\iomgr\gethostname_sysconf.c">
+    </ClCompile>
     <ClCompile Include="$(SolutionDir)\..\src\core\lib\iomgr\iocp_windows.c">
     </ClCompile>
     <ClCompile Include="$(SolutionDir)\..\src\core\lib\iomgr\iomgr.c">
@@ -884,6 +893,8 @@
     </ClCompile>
     <ClCompile Include="$(SolutionDir)\..\src\core\tsi\ssl_transport_security.c">
     </ClCompile>
+    <ClCompile Include="$(SolutionDir)\..\src\core\tsi\transport_security_grpc.c">
+    </ClCompile>
     <ClCompile Include="$(SolutionDir)\..\src\core\tsi\transport_security.c">
     </ClCompile>
     <ClCompile Include="$(SolutionDir)\..\src\core\tsi\transport_security_adapter.c">
diff --git a/vsprojects/vcxproj/grpc/grpc.vcxproj.filters b/vsprojects/vcxproj/grpc/grpc.vcxproj.filters
index 662eddf..6879047 100644
--- a/vsprojects/vcxproj/grpc/grpc.vcxproj.filters
+++ b/vsprojects/vcxproj/grpc/grpc.vcxproj.filters
@@ -94,6 +94,15 @@
     <ClCompile Include="$(SolutionDir)\..\src\core\lib\iomgr\executor.c">
       <Filter>src\core\lib\iomgr</Filter>
     </ClCompile>
+    <ClCompile Include="$(SolutionDir)\..\src\core\lib\iomgr\gethostname_fallback.c">
+      <Filter>src\core\lib\iomgr</Filter>
+    </ClCompile>
+    <ClCompile Include="$(SolutionDir)\..\src\core\lib\iomgr\gethostname_host_name_max.c">
+      <Filter>src\core\lib\iomgr</Filter>
+    </ClCompile>
+    <ClCompile Include="$(SolutionDir)\..\src\core\lib\iomgr\gethostname_sysconf.c">
+      <Filter>src\core\lib\iomgr</Filter>
+    </ClCompile>
     <ClCompile Include="$(SolutionDir)\..\src\core\lib\iomgr\iocp_windows.c">
       <Filter>src\core\lib\iomgr</Filter>
     </ClCompile>
@@ -547,6 +556,9 @@
     <ClCompile Include="$(SolutionDir)\..\src\core\tsi\ssl_transport_security.c">
       <Filter>src\core\tsi</Filter>
     </ClCompile>
+    <ClCompile Include="$(SolutionDir)\..\src\core\tsi\transport_security_grpc.c">
+      <Filter>src\core\tsi</Filter>
+    </ClCompile>
     <ClCompile Include="$(SolutionDir)\..\src\core\tsi\transport_security.c">
       <Filter>src\core\tsi</Filter>
     </ClCompile>
@@ -1001,6 +1013,9 @@
     <ClInclude Include="$(SolutionDir)\..\src\core\tsi\ssl_types.h">
       <Filter>src\core\tsi</Filter>
     </ClInclude>
+    <ClInclude Include="$(SolutionDir)\..\src\core\tsi\transport_security_grpc.h">
+      <Filter>src\core\tsi</Filter>
+    </ClInclude>
     <ClInclude Include="$(SolutionDir)\..\src\core\tsi\transport_security.h">
       <Filter>src\core\tsi</Filter>
     </ClInclude>
@@ -1163,6 +1178,9 @@
     <ClInclude Include="$(SolutionDir)\..\src\core\lib\iomgr\executor.h">
       <Filter>src\core\lib\iomgr</Filter>
     </ClInclude>
+    <ClInclude Include="$(SolutionDir)\..\src\core\lib\iomgr\gethostname.h">
+      <Filter>src\core\lib\iomgr</Filter>
+    </ClInclude>
     <ClInclude Include="$(SolutionDir)\..\src\core\lib\iomgr\iocp_windows.h">
       <Filter>src\core\lib\iomgr</Filter>
     </ClInclude>
@@ -1331,6 +1349,9 @@
     <ClInclude Include="$(SolutionDir)\..\src\core\lib\slice\slice_string_helpers.h">
       <Filter>src\core\lib\slice</Filter>
     </ClInclude>
+    <ClInclude Include="$(SolutionDir)\..\src\core\lib\surface\alarm_internal.h">
+      <Filter>src\core\lib\surface</Filter>
+    </ClInclude>
     <ClInclude Include="$(SolutionDir)\..\src\core\lib\surface\api_trace.h">
       <Filter>src\core\lib\surface</Filter>
     </ClInclude>
diff --git a/vsprojects/vcxproj/grpc_test_util/grpc_test_util.vcxproj b/vsprojects/vcxproj/grpc_test_util/grpc_test_util.vcxproj
index fa31dbe..1766e24 100644
--- a/vsprojects/vcxproj/grpc_test_util/grpc_test_util.vcxproj
+++ b/vsprojects/vcxproj/grpc_test_util/grpc_test_util.vcxproj
@@ -329,6 +329,12 @@
     </ClCompile>
     <ClCompile Include="$(SolutionDir)\..\src\core\lib\iomgr\executor.c">
     </ClCompile>
+    <ClCompile Include="$(SolutionDir)\..\src\core\lib\iomgr\gethostname_fallback.c">
+    </ClCompile>
+    <ClCompile Include="$(SolutionDir)\..\src\core\lib\iomgr\gethostname_host_name_max.c">
+    </ClCompile>
+    <ClCompile Include="$(SolutionDir)\..\src\core\lib\iomgr\gethostname_sysconf.c">
+    </ClCompile>
     <ClCompile Include="$(SolutionDir)\..\src\core\lib\iomgr\iocp_windows.c">
     </ClCompile>
     <ClCompile Include="$(SolutionDir)\..\src\core\lib\iomgr\iomgr.c">
diff --git a/vsprojects/vcxproj/grpc_test_util/grpc_test_util.vcxproj.filters b/vsprojects/vcxproj/grpc_test_util/grpc_test_util.vcxproj.filters
index fc9f64a..8516a07 100644
--- a/vsprojects/vcxproj/grpc_test_util/grpc_test_util.vcxproj.filters
+++ b/vsprojects/vcxproj/grpc_test_util/grpc_test_util.vcxproj.filters
@@ -151,6 +151,15 @@
     <ClCompile Include="$(SolutionDir)\..\src\core\lib\iomgr\executor.c">
       <Filter>src\core\lib\iomgr</Filter>
     </ClCompile>
+    <ClCompile Include="$(SolutionDir)\..\src\core\lib\iomgr\gethostname_fallback.c">
+      <Filter>src\core\lib\iomgr</Filter>
+    </ClCompile>
+    <ClCompile Include="$(SolutionDir)\..\src\core\lib\iomgr\gethostname_host_name_max.c">
+      <Filter>src\core\lib\iomgr</Filter>
+    </ClCompile>
+    <ClCompile Include="$(SolutionDir)\..\src\core\lib\iomgr\gethostname_sysconf.c">
+      <Filter>src\core\lib\iomgr</Filter>
+    </ClCompile>
     <ClCompile Include="$(SolutionDir)\..\src\core\lib\iomgr\iocp_windows.c">
       <Filter>src\core\lib\iomgr</Filter>
     </ClCompile>
diff --git a/vsprojects/vcxproj/grpc_test_util_unsecure/grpc_test_util_unsecure.vcxproj b/vsprojects/vcxproj/grpc_test_util_unsecure/grpc_test_util_unsecure.vcxproj
index 457dbd5..c92f0d1 100644
--- a/vsprojects/vcxproj/grpc_test_util_unsecure/grpc_test_util_unsecure.vcxproj
+++ b/vsprojects/vcxproj/grpc_test_util_unsecure/grpc_test_util_unsecure.vcxproj
@@ -317,6 +317,12 @@
     </ClCompile>
     <ClCompile Include="$(SolutionDir)\..\src\core\lib\iomgr\executor.c">
     </ClCompile>
+    <ClCompile Include="$(SolutionDir)\..\src\core\lib\iomgr\gethostname_fallback.c">
+    </ClCompile>
+    <ClCompile Include="$(SolutionDir)\..\src\core\lib\iomgr\gethostname_host_name_max.c">
+    </ClCompile>
+    <ClCompile Include="$(SolutionDir)\..\src\core\lib\iomgr\gethostname_sysconf.c">
+    </ClCompile>
     <ClCompile Include="$(SolutionDir)\..\src\core\lib\iomgr\iocp_windows.c">
     </ClCompile>
     <ClCompile Include="$(SolutionDir)\..\src\core\lib\iomgr\iomgr.c">
diff --git a/vsprojects/vcxproj/grpc_test_util_unsecure/grpc_test_util_unsecure.vcxproj.filters b/vsprojects/vcxproj/grpc_test_util_unsecure/grpc_test_util_unsecure.vcxproj.filters
index 49e886d..df34bdb 100644
--- a/vsprojects/vcxproj/grpc_test_util_unsecure/grpc_test_util_unsecure.vcxproj.filters
+++ b/vsprojects/vcxproj/grpc_test_util_unsecure/grpc_test_util_unsecure.vcxproj.filters
@@ -136,6 +136,15 @@
     <ClCompile Include="$(SolutionDir)\..\src\core\lib\iomgr\executor.c">
       <Filter>src\core\lib\iomgr</Filter>
     </ClCompile>
+    <ClCompile Include="$(SolutionDir)\..\src\core\lib\iomgr\gethostname_fallback.c">
+      <Filter>src\core\lib\iomgr</Filter>
+    </ClCompile>
+    <ClCompile Include="$(SolutionDir)\..\src\core\lib\iomgr\gethostname_host_name_max.c">
+      <Filter>src\core\lib\iomgr</Filter>
+    </ClCompile>
+    <ClCompile Include="$(SolutionDir)\..\src\core\lib\iomgr\gethostname_sysconf.c">
+      <Filter>src\core\lib\iomgr</Filter>
+    </ClCompile>
     <ClCompile Include="$(SolutionDir)\..\src\core\lib\iomgr\iocp_windows.c">
       <Filter>src\core\lib\iomgr</Filter>
     </ClCompile>
diff --git a/vsprojects/vcxproj/grpc_unsecure/grpc_unsecure.vcxproj b/vsprojects/vcxproj/grpc_unsecure/grpc_unsecure.vcxproj
index c0ce8f0..945ca2f 100644
--- a/vsprojects/vcxproj/grpc_unsecure/grpc_unsecure.vcxproj
+++ b/vsprojects/vcxproj/grpc_unsecure/grpc_unsecure.vcxproj
@@ -365,6 +365,7 @@
     <ClInclude Include="$(SolutionDir)\..\src\core\lib\iomgr\ev_posix.h" />
     <ClInclude Include="$(SolutionDir)\..\src\core\lib\iomgr\exec_ctx.h" />
     <ClInclude Include="$(SolutionDir)\..\src\core\lib\iomgr\executor.h" />
+    <ClInclude Include="$(SolutionDir)\..\src\core\lib\iomgr\gethostname.h" />
     <ClInclude Include="$(SolutionDir)\..\src\core\lib\iomgr\iocp_windows.h" />
     <ClInclude Include="$(SolutionDir)\..\src\core\lib\iomgr\iomgr.h" />
     <ClInclude Include="$(SolutionDir)\..\src\core\lib\iomgr\iomgr_internal.h" />
@@ -421,6 +422,7 @@
     <ClInclude Include="$(SolutionDir)\..\src\core\lib\slice\slice_hash_table.h" />
     <ClInclude Include="$(SolutionDir)\..\src\core\lib\slice\slice_internal.h" />
     <ClInclude Include="$(SolutionDir)\..\src\core\lib\slice\slice_string_helpers.h" />
+    <ClInclude Include="$(SolutionDir)\..\src\core\lib\surface\alarm_internal.h" />
     <ClInclude Include="$(SolutionDir)\..\src\core\lib\surface\api_trace.h" />
     <ClInclude Include="$(SolutionDir)\..\src\core\lib\surface\call.h" />
     <ClInclude Include="$(SolutionDir)\..\src\core\lib\surface\call_test_only.h" />
@@ -548,6 +550,12 @@
     </ClCompile>
     <ClCompile Include="$(SolutionDir)\..\src\core\lib\iomgr\executor.c">
     </ClCompile>
+    <ClCompile Include="$(SolutionDir)\..\src\core\lib\iomgr\gethostname_fallback.c">
+    </ClCompile>
+    <ClCompile Include="$(SolutionDir)\..\src\core\lib\iomgr\gethostname_host_name_max.c">
+    </ClCompile>
+    <ClCompile Include="$(SolutionDir)\..\src\core\lib\iomgr\gethostname_sysconf.c">
+    </ClCompile>
     <ClCompile Include="$(SolutionDir)\..\src\core\lib\iomgr\iocp_windows.c">
     </ClCompile>
     <ClCompile Include="$(SolutionDir)\..\src\core\lib\iomgr\iomgr.c">
diff --git a/vsprojects/vcxproj/grpc_unsecure/grpc_unsecure.vcxproj.filters b/vsprojects/vcxproj/grpc_unsecure/grpc_unsecure.vcxproj.filters
index 2d2a820..deb3433 100644
--- a/vsprojects/vcxproj/grpc_unsecure/grpc_unsecure.vcxproj.filters
+++ b/vsprojects/vcxproj/grpc_unsecure/grpc_unsecure.vcxproj.filters
@@ -97,6 +97,15 @@
     <ClCompile Include="$(SolutionDir)\..\src\core\lib\iomgr\executor.c">
       <Filter>src\core\lib\iomgr</Filter>
     </ClCompile>
+    <ClCompile Include="$(SolutionDir)\..\src\core\lib\iomgr\gethostname_fallback.c">
+      <Filter>src\core\lib\iomgr</Filter>
+    </ClCompile>
+    <ClCompile Include="$(SolutionDir)\..\src\core\lib\iomgr\gethostname_host_name_max.c">
+      <Filter>src\core\lib\iomgr</Filter>
+    </ClCompile>
+    <ClCompile Include="$(SolutionDir)\..\src\core\lib\iomgr\gethostname_sysconf.c">
+      <Filter>src\core\lib\iomgr</Filter>
+    </ClCompile>
     <ClCompile Include="$(SolutionDir)\..\src\core\lib\iomgr\iocp_windows.c">
       <Filter>src\core\lib\iomgr</Filter>
     </ClCompile>
@@ -992,6 +1001,9 @@
     <ClInclude Include="$(SolutionDir)\..\src\core\lib\iomgr\executor.h">
       <Filter>src\core\lib\iomgr</Filter>
     </ClInclude>
+    <ClInclude Include="$(SolutionDir)\..\src\core\lib\iomgr\gethostname.h">
+      <Filter>src\core\lib\iomgr</Filter>
+    </ClInclude>
     <ClInclude Include="$(SolutionDir)\..\src\core\lib\iomgr\iocp_windows.h">
       <Filter>src\core\lib\iomgr</Filter>
     </ClInclude>
@@ -1160,6 +1172,9 @@
     <ClInclude Include="$(SolutionDir)\..\src\core\lib\slice\slice_string_helpers.h">
       <Filter>src\core\lib\slice</Filter>
     </ClInclude>
+    <ClInclude Include="$(SolutionDir)\..\src\core\lib\surface\alarm_internal.h">
+      <Filter>src\core\lib\surface</Filter>
+    </ClInclude>
     <ClInclude Include="$(SolutionDir)\..\src\core\lib\surface\api_trace.h">
       <Filter>src\core\lib\surface</Filter>
     </ClInclude>