Shared subchannel sketch
diff --git a/BUILD b/BUILD
index 2b386fb..a74d2d1 100644
--- a/BUILD
+++ b/BUILD
@@ -178,6 +178,7 @@
     "src/core/client_config/resolvers/sockaddr_resolver.h",
     "src/core/client_config/subchannel.h",
     "src/core/client_config/subchannel_factory.h",
+    "src/core/client_config/subchannel_index.h",
     "src/core/client_config/uri_parser.h",
     "src/core/compression/algorithm_metadata.h",
     "src/core/compression/message_compress.h",
@@ -316,6 +317,7 @@
     "src/core/client_config/resolvers/sockaddr_resolver.c",
     "src/core/client_config/subchannel.c",
     "src/core/client_config/subchannel_factory.c",
+    "src/core/client_config/subchannel_index.c",
     "src/core/client_config/uri_parser.c",
     "src/core/compression/algorithm.c",
     "src/core/compression/message_compress.c",
@@ -469,6 +471,7 @@
     "src/core/client_config/resolvers/sockaddr_resolver.h",
     "src/core/client_config/subchannel.h",
     "src/core/client_config/subchannel_factory.h",
+    "src/core/client_config/subchannel_index.h",
     "src/core/client_config/uri_parser.h",
     "src/core/compression/algorithm_metadata.h",
     "src/core/compression/message_compress.h",
@@ -587,6 +590,7 @@
     "src/core/client_config/resolvers/sockaddr_resolver.c",
     "src/core/client_config/subchannel.c",
     "src/core/client_config/subchannel_factory.c",
+    "src/core/client_config/subchannel_index.c",
     "src/core/client_config/uri_parser.c",
     "src/core/compression/algorithm.c",
     "src/core/compression/message_compress.c",
@@ -1121,6 +1125,7 @@
     "src/core/client_config/resolvers/sockaddr_resolver.c",
     "src/core/client_config/subchannel.c",
     "src/core/client_config/subchannel_factory.c",
+    "src/core/client_config/subchannel_index.c",
     "src/core/client_config/uri_parser.c",
     "src/core/compression/algorithm.c",
     "src/core/compression/message_compress.c",
@@ -1272,6 +1277,7 @@
     "src/core/client_config/resolvers/sockaddr_resolver.h",
     "src/core/client_config/subchannel.h",
     "src/core/client_config/subchannel_factory.h",
+    "src/core/client_config/subchannel_index.h",
     "src/core/client_config/uri_parser.h",
     "src/core/compression/algorithm_metadata.h",
     "src/core/compression/message_compress.h",