Add forced completion queue poll to ensure that waitForReady uses current connectivity state

packages/grpc-native-core/ext/completion_queue.cc

@@ -35,7 +35,7 @@ grpc_completion_queue *queue;
 uv_prepare_t prepare;
 int pending_batches;
 
-void drain_completion_queue(uv_prepare_t *handle) {
+static void drain_completion_queue(uv_prepare_t *handle) {
   Nan::HandleScope scope;
   grpc_event event;
   (void)handle;
@@ -53,9 +53,9 @@ void drain_completion_queue(uv_prepare_t *handle) {
       CompleteTag(event.tag, error_message);
       grpc::node::DestroyTag(event.tag);
       pending_batches--;
-      if (pending_batches == 0) {
-        uv_prepare_stop(&prepare);
-      }
+    }
+    if (pending_batches == 0) {
+      uv_prepare_stop(&prepare);
     }
   } while (event.type != GRPC_QUEUE_TIMEOUT);
 }
@@ -76,5 +76,15 @@ void CompletionQueueInit(Local<Object> exports) {
   pending_batches = 0;
 }
 
+void CompletionQueueForcePoll() {
+  /* This sets the prepare object to poll on the completion queue the next time
+   * Node polls for IO. But it doesn't increment the number of pending batches,
+   * so it will immediately stop polling after that unless there is an
+   * intervening CompletionQueueNext call */
+  if (pending_batches == 0) {
+    uv_prepare_start(&prepare, drain_completion_queue);
+  }
+}
+
 }  // namespace node
 }  // namespace grpc

packages/grpc-native-core/ext/node_grpc.cc

@@ -265,6 +265,10 @@ NAN_METHOD(SetLogVerbosity) {
   gpr_set_log_verbosity(severity);
 }
 
+NAN_METHOD(ForcePoll) {
+  grpc::node::CompletionQueueForcePoll();
+}
+
 void init(Local<Object> exports) {
   Nan::HandleScope scope;
   grpc_init();
@@ -306,6 +310,9 @@ void init(Local<Object> exports) {
   Nan::Set(exports, Nan::New("setLogVerbosity").ToLocalChecked(),
            Nan::GetFunction(Nan::New<FunctionTemplate>(SetLogVerbosity))
                .ToLocalChecked());
+  Nan::Set(exports, Nan::New("forcePoll").ToLocalChecked(),
+           Nan::GetFunction(Nan::New<FunctionTemplate>(ForcePoll))
+               .ToLocalChecked());
 }
 
 NODE_MODULE(grpc_node, init)

packages/grpc-native-core/src/client.js

@@ -800,7 +800,10 @@ Client.prototype.waitForReady = function(deadline, callback) {
       self.$channel.watchConnectivityState(new_state, deadline, checkState);
     }
   };
-  checkState();
+  /* Force a single round of polling to ensure that the channel state is up
+   * to date */
+  grpc.forcePoll();
+  setImmediate(checkState);
 };
 
 /**