Readd grpclb fallback
diff --git a/src/core/ext/filters/client_channel/lb_policy/grpclb/grpclb.c b/src/core/ext/filters/client_channel/lb_policy/grpclb/grpclb.c
index 05a106f..8dc81b4 100644
--- a/src/core/ext/filters/client_channel/lb_policy/grpclb/grpclb.c
+++ b/src/core/ext/filters/client_channel/lb_policy/grpclb/grpclb.c
@@ -123,6 +123,7 @@
#define GRPC_GRPCLB_RECONNECT_BACKOFF_MULTIPLIER 1.6
#define GRPC_GRPCLB_RECONNECT_MAX_BACKOFF_SECONDS 120
#define GRPC_GRPCLB_RECONNECT_JITTER 0.2
+#define GRPC_GRPCLB_DEFAULT_FALLBACK_TIMEOUT_MS 10000
grpc_tracer_flag grpc_lb_glb_trace = GRPC_TRACER_INITIALIZER(false, "glb");
@@ -299,6 +300,10 @@
/** timeout in milliseconds for the LB call. 0 means no deadline. */
int lb_call_timeout_ms;
+ /** timeout in milliseconds for before using fallback backend addresses.
+ * 0 means not using fallback. */
+ int lb_fallback_timeout_ms;
+
/** for communicating with the LB server */
grpc_channel *lb_channel;
@@ -325,6 +330,9 @@
* Otherwise, we delegate to the RR policy. */
size_t serverlist_index;
+ /** stores the backend addresses from the resolver */
+ grpc_lb_addresses *fallback_backend_addresses;
+
/** list of picks that are waiting on RR's policy connectivity */
pending_pick *pending_picks;
@@ -345,6 +353,9 @@
/** is \a lb_call_retry_timer active? */
bool retry_timer_active;
+ /** is \a lb_fallback_timer active? */
+ bool fallback_timer_active;
+
/** called upon changes to the LB channel's connectivity. */
grpc_closure lb_channel_on_connectivity_changed;
@@ -364,6 +375,9 @@
/* LB call retry timer callback. */
grpc_closure lb_on_call_retry;
+ /* LB fallback timer callback. */
+ grpc_closure lb_on_fallback;
+
grpc_call *lb_call; /* streaming call to the LB server, */
grpc_metadata_array lb_initial_metadata_recv; /* initial MD from LB server */
@@ -387,6 +401,9 @@
/** LB call retry timer */
grpc_timer lb_call_retry_timer;
+ /** LB fallback timer */
+ grpc_timer lb_fallback_timer;
+
bool seen_initial_response;
/* Stats for client-side load reporting. Should be unreffed and
@@ -532,6 +549,32 @@
return lb_addresses;
}
+/* Returns the backend addresses extracted from the given addresses */
+static grpc_lb_addresses *extract_backend_addresses_locked(
+ grpc_exec_ctx *exec_ctx, const grpc_lb_addresses *addresses) {
+ /* first pass: count the number of backend addresses */
+ size_t num_backends = 0;
+ for (size_t i = 0; i < addresses->num_addresses; ++i) {
+ if (!addresses->addresses[i].is_balancer) {
+ ++num_backends;
+ }
+ }
+ /* second pass: actually populate the addresses and (empty) LB tokens */
+ grpc_lb_addresses *backend_addresses =
+ grpc_lb_addresses_create(num_backends, &lb_token_vtable);
+ size_t num_copied = 0;
+ for (size_t i = 0; i < addresses->num_addresses; ++i) {
+ if (addresses->addresses[i].is_balancer) continue;
+ const grpc_resolved_address *addr = &addresses->addresses[i].address;
+ grpc_lb_addresses_set_address(backend_addresses, num_copied, &addr->addr,
+ addr->len, false /* is_balancer */,
+ NULL /* balancer_name */,
+ (void *)GRPC_MDELEM_LB_TOKEN_EMPTY.payload);
+ ++num_copied;
+ }
+ return backend_addresses;
+}
+
static void update_lb_connectivity_status_locked(
grpc_exec_ctx *exec_ctx, glb_lb_policy *glb_policy,
grpc_connectivity_state rr_state, grpc_error *rr_state_error) {
@@ -599,35 +642,38 @@
grpc_exec_ctx *exec_ctx, glb_lb_policy *glb_policy,
const grpc_lb_policy_pick_args *pick_args, bool force_async,
grpc_connected_subchannel **target, wrapped_rr_closure_arg *wc_arg) {
- // Look at the index into the serverlist to see if we should drop this call.
- grpc_grpclb_server *server =
- glb_policy->serverlist->servers[glb_policy->serverlist_index++];
- if (glb_policy->serverlist_index == glb_policy->serverlist->num_servers) {
- glb_policy->serverlist_index = 0; // Wrap-around.
- }
- if (server->drop) {
- // Not using the RR policy, so unref it.
- if (GRPC_TRACER_ON(grpc_lb_glb_trace)) {
- gpr_log(GPR_INFO, "Unreffing RR for drop (0x%" PRIxPTR ")",
- (intptr_t)wc_arg->rr_policy);
+ // Check for drops if we are not using fallback backend addresses.
+ if (glb_policy->serverlist != NULL) {
+ // Look at the index into the serverlist to see if we should drop this call.
+ grpc_grpclb_server *server =
+ glb_policy->serverlist->servers[glb_policy->serverlist_index++];
+ if (glb_policy->serverlist_index == glb_policy->serverlist->num_servers) {
+ glb_policy->serverlist_index = 0; // Wrap-around.
}
- GRPC_LB_POLICY_UNREF(exec_ctx, wc_arg->rr_policy, "glb_pick_sync");
- // Update client load reporting stats to indicate the number of
- // dropped calls. Note that we have to do this here instead of in
- // the client_load_reporting filter, because we do not create a
- // subchannel call (and therefore no client_load_reporting filter)
- // for dropped calls.
- grpc_grpclb_client_stats_add_call_dropped_locked(server->load_balance_token,
- wc_arg->client_stats);
- grpc_grpclb_client_stats_unref(wc_arg->client_stats);
- if (force_async) {
- GPR_ASSERT(wc_arg->wrapped_closure != NULL);
- GRPC_CLOSURE_SCHED(exec_ctx, wc_arg->wrapped_closure, GRPC_ERROR_NONE);
+ if (server->drop) {
+ // Not using the RR policy, so unref it.
+ if (GRPC_TRACER_ON(grpc_lb_glb_trace)) {
+ gpr_log(GPR_INFO, "Unreffing RR for drop (0x%" PRIxPTR ")",
+ (intptr_t)wc_arg->rr_policy);
+ }
+ GRPC_LB_POLICY_UNREF(exec_ctx, wc_arg->rr_policy, "glb_pick_sync");
+ // Update client load reporting stats to indicate the number of
+ // dropped calls. Note that we have to do this here instead of in
+ // the client_load_reporting filter, because we do not create a
+ // subchannel call (and therefore no client_load_reporting filter)
+ // for dropped calls.
+ grpc_grpclb_client_stats_add_call_dropped_locked(
+ server->load_balance_token, wc_arg->client_stats);
+ grpc_grpclb_client_stats_unref(wc_arg->client_stats);
+ if (force_async) {
+ GPR_ASSERT(wc_arg->wrapped_closure != NULL);
+ GRPC_CLOSURE_SCHED(exec_ctx, wc_arg->wrapped_closure, GRPC_ERROR_NONE);
+ gpr_free(wc_arg->free_when_done);
+ return false;
+ }
gpr_free(wc_arg->free_when_done);
- return false;
+ return true;
}
- gpr_free(wc_arg->free_when_done);
- return true;
}
// Pick via the RR policy.
const bool pick_done = grpc_lb_policy_pick_locked(
@@ -665,8 +711,18 @@
static grpc_lb_policy_args *lb_policy_args_create(grpc_exec_ctx *exec_ctx,
glb_lb_policy *glb_policy) {
- grpc_lb_addresses *addresses =
- process_serverlist_locked(exec_ctx, glb_policy->serverlist);
+ grpc_lb_addresses *addresses;
+ if (glb_policy->serverlist != NULL) {
+ GPR_ASSERT(glb_policy->serverlist->num_servers > 0);
+ addresses = process_serverlist_locked(exec_ctx, glb_policy->serverlist);
+ } else {
+ // If rr_handover_locked() is invoked when we haven't received any
+ // serverlist from the balancer, we use the fallback backends returned by
+ // the resolver. Note that the fallback backend list may be empty, in which
+ // case the new round_robin policy will keep the requested picks pending.
+ GPR_ASSERT(glb_policy->fallback_backend_addresses != NULL);
+ addresses = grpc_lb_addresses_copy(glb_policy->fallback_backend_addresses);
+ }
GPR_ASSERT(addresses != NULL);
grpc_lb_policy_args *args = (grpc_lb_policy_args *)gpr_zalloc(sizeof(*args));
args->client_channel_factory = glb_policy->cc_factory;
@@ -772,8 +828,6 @@
/* glb_policy->rr_policy may be NULL (initial handover) */
static void rr_handover_locked(grpc_exec_ctx *exec_ctx,
glb_lb_policy *glb_policy) {
- GPR_ASSERT(glb_policy->serverlist != NULL &&
- glb_policy->serverlist->num_servers > 0);
if (glb_policy->shutting_down) return;
grpc_lb_policy_args *args = lb_policy_args_create(exec_ctx, glb_policy);
GPR_ASSERT(args != NULL);
@@ -922,6 +976,9 @@
if (glb_policy->serverlist != NULL) {
grpc_grpclb_destroy_serverlist(glb_policy->serverlist);
}
+ if (glb_policy->fallback_backend_addresses != NULL) {
+ grpc_lb_addresses_destroy(exec_ctx, glb_policy->fallback_backend_addresses);
+ }
grpc_fake_resolver_response_generator_unref(glb_policy->response_generator);
grpc_subchannel_index_unref();
if (glb_policy->pending_update_args != NULL) {
@@ -1063,10 +1120,28 @@
GRPC_ERROR_UNREF(error);
}
+static void lb_on_fallback_timer_locked(grpc_exec_ctx *exec_ctx, void *arg,
+ grpc_error *error);
static void query_for_backends_locked(grpc_exec_ctx *exec_ctx,
glb_lb_policy *glb_policy);
static void start_picking_locked(grpc_exec_ctx *exec_ctx,
glb_lb_policy *glb_policy) {
+ /* start a timer to fall back */
+ if (glb_policy->lb_fallback_timeout_ms > 0 &&
+ glb_policy->serverlist == NULL && !glb_policy->fallback_timer_active) {
+ gpr_timespec now = gpr_now(GPR_CLOCK_MONOTONIC);
+ gpr_timespec deadline = gpr_time_add(
+ now,
+ gpr_time_from_millis(glb_policy->lb_fallback_timeout_ms, GPR_TIMESPAN));
+ GRPC_LB_POLICY_WEAK_REF(&glb_policy->base, "grpclb_fallback_timer");
+ GRPC_CLOSURE_INIT(&glb_policy->lb_on_fallback, lb_on_fallback_timer_locked,
+ glb_policy,
+ grpc_combiner_scheduler(glb_policy->base.combiner));
+ glb_policy->fallback_timer_active = true;
+ grpc_timer_init(exec_ctx, &glb_policy->lb_fallback_timer, deadline,
+ &glb_policy->lb_on_fallback, now);
+ }
+
glb_policy->started_picking = true;
gpr_backoff_reset(&glb_policy->lb_call_backoff_state);
query_for_backends_locked(exec_ctx, glb_policy);
@@ -1545,6 +1620,15 @@
if (glb_policy->serverlist != NULL) {
/* dispose of the old serverlist */
grpc_grpclb_destroy_serverlist(glb_policy->serverlist);
+ } else {
+ /* or dispose of the fallback */
+ grpc_lb_addresses_destroy(exec_ctx,
+ glb_policy->fallback_backend_addresses);
+ glb_policy->fallback_backend_addresses = NULL;
+ if (glb_policy->fallback_timer_active) {
+ grpc_timer_cancel(exec_ctx, &glb_policy->lb_fallback_timer);
+ glb_policy->fallback_timer_active = false;
+ }
}
/* and update the copy in the glb_lb_policy instance. This
* serverlist instance will be destroyed either upon the next
@@ -1555,9 +1639,7 @@
}
} else {
if (GRPC_TRACER_ON(grpc_lb_glb_trace)) {
- gpr_log(GPR_INFO,
- "Received empty server list. Picks will stay pending until "
- "a response with > 0 servers is received");
+ gpr_log(GPR_INFO, "Received empty server list, ignoring.");
}
grpc_grpclb_destroy_serverlist(serverlist);
}
@@ -1592,6 +1674,27 @@
}
}
+static void lb_on_fallback_timer_locked(grpc_exec_ctx *exec_ctx, void *arg,
+ grpc_error *error) {
+ glb_lb_policy *glb_policy = (glb_lb_policy *)arg;
+ glb_policy->fallback_timer_active = false;
+ /* If we receive a serverlist after the timer fires but before this callback
+ * actually runs, don't fall back. */
+ if (glb_policy->serverlist == NULL) {
+ if (!glb_policy->shutting_down && error == GRPC_ERROR_NONE) {
+ if (GRPC_TRACER_ON(grpc_lb_glb_trace)) {
+ gpr_log(GPR_INFO,
+ "Falling back to use backends from resolver (grpclb %p)",
+ (void *)glb_policy);
+ }
+ GPR_ASSERT(glb_policy->fallback_backend_addresses != NULL);
+ rr_handover_locked(exec_ctx, glb_policy);
+ }
+ }
+ GRPC_LB_POLICY_WEAK_UNREF(exec_ctx, &glb_policy->base,
+ "grpclb_fallback_timer");
+}
+
static void lb_on_server_status_received_locked(grpc_exec_ctx *exec_ctx,
void *arg, grpc_error *error) {
glb_lb_policy *glb_policy = (glb_lb_policy *)arg;
@@ -1616,10 +1719,51 @@
}
}
+static void fallback_update_locked(grpc_exec_ctx *exec_ctx,
+ glb_lb_policy *glb_policy,
+ const grpc_lb_addresses *addresses) {
+ GPR_ASSERT(glb_policy->fallback_backend_addresses != NULL);
+ grpc_lb_addresses_destroy(exec_ctx, glb_policy->fallback_backend_addresses);
+ glb_policy->fallback_backend_addresses =
+ extract_backend_addresses_locked(exec_ctx, addresses);
+ if (glb_policy->lb_fallback_timeout_ms > 0 &&
+ !glb_policy->fallback_timer_active) {
+ rr_handover_locked(exec_ctx, glb_policy);
+ }
+}
+
static void glb_update_locked(grpc_exec_ctx *exec_ctx, grpc_lb_policy *policy,
const grpc_lb_policy_args *args) {
glb_lb_policy *glb_policy = (glb_lb_policy *)policy;
- if (glb_policy->updating_lb_channel) {
+ const grpc_arg *arg =
+ grpc_channel_args_find(args->args, GRPC_ARG_LB_ADDRESSES);
+ if (arg == NULL || arg->type != GRPC_ARG_POINTER) {
+ if (glb_policy->lb_channel == NULL) {
+ // If we don't have a current channel to the LB, go into TRANSIENT
+ // FAILURE.
+ grpc_connectivity_state_set(
+ exec_ctx, &glb_policy->state_tracker, GRPC_CHANNEL_TRANSIENT_FAILURE,
+ GRPC_ERROR_CREATE_FROM_STATIC_STRING("Missing update in args"),
+ "glb_update_missing");
+ } else {
+ // otherwise, keep using the current LB channel (ignore this update).
+ gpr_log(GPR_ERROR,
+ "No valid LB addresses channel arg for grpclb %p update, "
+ "ignoring.",
+ (void *)glb_policy);
+ }
+ return;
+ }
+ const grpc_lb_addresses *addresses =
+ (const grpc_lb_addresses *)arg->value.pointer.p;
+
+ if (glb_policy->serverlist == NULL) {
+ // If a non-empty serverlist hasn't been received from the balancer,
+ // propagate the update to fallback_backend_addresses.
+ fallback_update_locked(exec_ctx, glb_policy, addresses);
+ } else if (glb_policy->updating_lb_channel) {
+ // If we have recieved serverlist from the balancer, we need to defer update
+ // when there is an in-progress one.
if (GRPC_TRACER_ON(grpc_lb_glb_trace)) {
gpr_log(GPR_INFO,
"Update already in progress for grpclb %p. Deferring update.",
@@ -1640,31 +1784,11 @@
}
glb_policy->updating_lb_channel = true;
- // Propagate update to lb_channel (pick first).
- const grpc_arg *arg =
- grpc_channel_args_find(args->args, GRPC_ARG_LB_ADDRESSES);
- if (arg == NULL || arg->type != GRPC_ARG_POINTER) {
- if (glb_policy->lb_channel == NULL) {
- // If we don't have a current channel to the LB, go into TRANSIENT
- // FAILURE.
- grpc_connectivity_state_set(
- exec_ctx, &glb_policy->state_tracker, GRPC_CHANNEL_TRANSIENT_FAILURE,
- GRPC_ERROR_CREATE_FROM_STATIC_STRING("Missing update in args"),
- "glb_update_missing");
- } else {
- // otherwise, keep using the current LB channel (ignore this update).
- gpr_log(GPR_ERROR,
- "No valid LB addresses channel arg for grpclb %p update, "
- "ignoring.",
- (void *)glb_policy);
- }
- }
- const grpc_lb_addresses *addresses =
- (const grpc_lb_addresses *)arg->value.pointer.p;
GPR_ASSERT(glb_policy->lb_channel != NULL);
grpc_channel_args *lb_channel_args = build_lb_channel_args(
exec_ctx, addresses, glb_policy->response_generator, args->args);
- /* Propagate updates to the LB channel through the fake resolver */
+ /* Propagate updates to the LB channel (pick first) through the fake resolver
+ */
grpc_fake_resolver_response_generator_set_response(
exec_ctx, glb_policy->response_generator, lb_channel_args);
grpc_channel_args_destroy(exec_ctx, lb_channel_args);
@@ -1767,13 +1891,7 @@
static grpc_lb_policy *glb_create(grpc_exec_ctx *exec_ctx,
grpc_lb_policy_factory *factory,
grpc_lb_policy_args *args) {
- /* Count the number of gRPC-LB addresses. There must be at least one.
- * TODO(roth): For now, we ignore non-balancer addresses, but in the
- * future, we may change the behavior such that we fall back to using
- * the non-balancer addresses if we cannot reach any balancers. In the
- * fallback case, we should use the LB policy indicated by
- * GRPC_ARG_LB_POLICY_NAME (although if that specifies grpclb or is
- * unset, we should default to pick_first). */
+ /* Count the number of gRPC-LB addresses. There must be at least one. */
const grpc_arg *arg =
grpc_channel_args_find(args->args, GRPC_ARG_LB_ADDRESSES);
if (arg == NULL || arg->type != GRPC_ARG_POINTER) {
@@ -1809,6 +1927,11 @@
glb_policy->lb_call_timeout_ms =
grpc_channel_arg_get_integer(arg, (grpc_integer_options){0, 0, INT_MAX});
+ arg = grpc_channel_args_find(args->args, GRPC_ARG_GRPCLB_FALLBACK_TIMEOUT_MS);
+ glb_policy->lb_fallback_timeout_ms = grpc_channel_arg_get_integer(
+ arg, (grpc_integer_options){GRPC_GRPCLB_DEFAULT_FALLBACK_TIMEOUT_MS, 0,
+ INT_MAX});
+
// Make sure that GRPC_ARG_LB_POLICY_NAME is set in channel args,
// since we use this to trigger the client_load_reporting filter.
grpc_arg new_arg = grpc_channel_arg_string_create(
@@ -1817,6 +1940,11 @@
glb_policy->args = grpc_channel_args_copy_and_add_and_remove(
args->args, args_to_remove, GPR_ARRAY_SIZE(args_to_remove), &new_arg, 1);
+ /* Extract the backend addresses (may be empty) from the resolver for
+ * fallback. */
+ glb_policy->fallback_backend_addresses =
+ extract_backend_addresses_locked(exec_ctx, addresses);
+
/* Create a client channel over them to communicate with a LB service */
glb_policy->response_generator =
grpc_fake_resolver_response_generator_create();