RR: Initialize subchannel connectivity state

src/core/ext/filters/client_channel/lb_policy/round_robin/round_robin.c

@@ -811,19 +811,30 @@ static void rr_update_locked(grpc_exec_ctx *exec_ctx, grpc_lb_policy *policy,
     sc_args.args = new_args;
     grpc_subchannel *subchannel = grpc_client_channel_factory_create_subchannel(
         exec_ctx, args->client_channel_factory, &sc_args);
+    grpc_channel_args_destroy(exec_ctx, new_args);
+    grpc_error *error;
+    // Get the connectivity state of the subchannel. Already existing ones may
+    // be in a state other than INIT.
+    const grpc_connectivity_state subchannel_connectivity_state =
+        grpc_subchannel_check_connectivity(subchannel, &error);
+    if (error != GRPC_ERROR_NONE) {
+      // The subchannel is in error (e.g. shutting down). Ignore it.
+      GRPC_SUBCHANNEL_UNREF(exec_ctx, subchannel, "new_sc_connectivity_error");
+      GRPC_ERROR_UNREF(error);
+      continue;
+    }
     if (GRPC_TRACER_ON(grpc_lb_round_robin_trace)) {
       char *address_uri =
           grpc_sockaddr_to_uri(&addresses->addresses[i].address);
       gpr_log(
           GPR_DEBUG,
           "[RR %p] index %lu: Created subchannel %p for address uri %s into "
-          "subchannel_list %p",
+          "subchannel_list %p. Connectivity state %s",
           (void *)p, (unsigned long)subchannel_index, (void *)subchannel,
-          address_uri, (void *)subchannel_list);
+          address_uri, (void *)subchannel_list,
+          grpc_connectivity_state_name(subchannel_connectivity_state));
       gpr_free(address_uri);
     }
-    grpc_channel_args_destroy(exec_ctx, new_args);
-
     subchannel_data *sd = &subchannel_list->subchannels[subchannel_index++];
     sd->subchannel_list = subchannel_list;
     sd->subchannel = subchannel;
@@ -835,7 +846,7 @@ static void rr_update_locked(grpc_exec_ctx *exec_ctx, grpc_lb_policy *policy,
      * won't be referring to this value again and it'll be overwritten after
      * the first call to rr_connectivity_changed_locked */
     sd->prev_connectivity_state = GRPC_CHANNEL_INIT;
-    sd->curr_connectivity_state = GRPC_CHANNEL_IDLE;
+    sd->curr_connectivity_state = subchannel_connectivity_state;
     sd->user_data_vtable = addresses->user_data_vtable;
     if (sd->user_data_vtable != NULL) {
       sd->user_data =

test/cpp/end2end/client_lb_end2end_test.cc

@@ -450,6 +450,43 @@ TEST_F(ClientLbEnd2endTest, RoundRobinUpdates) {
   EXPECT_EQ("round_robin", channel_->GetLoadBalancingPolicyName());
 }
 
+TEST_F(ClientLbEnd2endTest, RoundRobinUpdateInError) {
+  // Start servers and send one RPC per server.
+  const int kNumServers = 3;
+  StartServers(kNumServers);
+  ResetStub("round_robin");
+  std::vector<int> ports;
+
+  // Start with a single server.
+  ports.emplace_back(servers_[0]->port_);
+  SetNextResolution(ports);
+  WaitForServer(0);
+  // Send RPCs. They should all go servers_[0]
+  for (size_t i = 0; i < 10; ++i) SendRpc();
+  EXPECT_EQ(10, servers_[0]->service_.request_count());
+  EXPECT_EQ(0, servers_[1]->service_.request_count());
+  EXPECT_EQ(0, servers_[2]->service_.request_count());
+  servers_[0]->service_.ResetCounters();
+
+  // All servers, but one is shutdown.
+  servers_[1]->Shutdown(false);
+  ports.clear();
+  ports.emplace_back(servers_[0]->port_);
+  ports.emplace_back(servers_[1]->port_);
+  ports.emplace_back(servers_[2]->port_);
+  SetNextResolution(ports);
+  WaitForServer(0);
+  WaitForServer(2);
+
+  // Send three RPCs, one per server.
+  for (size_t i = 0; i < kNumServers; ++i) SendRpc();
+  // The server in shutdown shouldn't receive any.
+  EXPECT_EQ(0, servers_[1]->service_.request_count());
+
+  // Check LB policy name for the channel.
+  EXPECT_EQ("round_robin", channel_->GetLoadBalancingPolicyName());
+}
+
 TEST_F(ClientLbEnd2endTest, RoundRobinManyUpdates) {
   // Start servers and send one RPC per server.
   const int kNumServers = 3;