From c0f7afec327ab2523bd9970a280da7f49c5fccce Mon Sep 17 00:00:00 2001
From: Kelvin Jin <kelvinjin@google.com>
Date: Thu, 12 Apr 2018 11:59:34 -0700
Subject: [PATCH] js: only listen for channel connect event once

---
 packages/grpc-js-core/src/call.ts    |  2 +-
 packages/grpc-js-core/src/channel.ts | 40 +++++++++++++++++++++++-----
 packages/grpc-js-core/src/client.ts  |  6 +++++
 3 files changed, 40 insertions(+), 8 deletions(-)

diff --git a/packages/grpc-js-core/src/call.ts b/packages/grpc-js-core/src/call.ts
index af305b24..4344dfeb 100644
--- a/packages/grpc-js-core/src/call.ts
+++ b/packages/grpc-js-core/src/call.ts
@@ -87,13 +87,13 @@ function setUpReadableStream<ResponseType>(
     stream.push(null);
   });
   call.on('status', (status: StatusObject) => {
-    stream.emit('status', status);
     if (status.code !== Status.OK) {
       const statusName = _.invert(Status)[status.code];
       const message: string = `${status.code} ${statusName}: ${status.details}`;
       const error: ServiceError = Object.assign(new Error(status.details), status);
       stream.emit('error', error);
     }
+    stream.emit('status', status);
   });
   call.pause();
 }
diff --git a/packages/grpc-js-core/src/channel.ts b/packages/grpc-js-core/src/channel.ts
index 8e8e38e7..e710b733 100644
--- a/packages/grpc-js-core/src/channel.ts
+++ b/packages/grpc-js-core/src/channel.ts
@@ -85,6 +85,8 @@ export class Http2Channel extends EventEmitter implements Channel {
   private readonly target: url.URL;
   private readonly defaultAuthority: string;
   private connectivityState: ConnectivityState = ConnectivityState.IDLE;
+  // Helper Promise object only used in the implementation of connect().
+  private connecting: Promise<void>|null = null;
   /* For now, we have up to one subchannel, which will exist as long as we are
    * connecting or trying to connect */
   private subChannel: http2.ClientHttp2Session|null = null;
@@ -127,6 +129,7 @@ export class Http2Channel extends EventEmitter implements Channel {
         this.subChannel.removeListener('connect', this.subChannelConnectCallback);
         this.subChannel.removeListener('close', this.subChannelCloseCallback);
         this.subChannel = null;
+        this.emit('shutdown');
         clearTimeout(this.backoffTimerId);
       }
       break;
@@ -279,15 +282,38 @@ export class Http2Channel extends EventEmitter implements Channel {
     return stream;
   }
 
+  /**
+   * Attempts to connect, returning a Promise that resolves when the connection
+   * is successful, or rejects if the channel is shut down.
+   */
   connect(): Promise<void> {
-    return new Promise((resolve) => {
-      this.transitionToState([ConnectivityState.IDLE], ConnectivityState.CONNECTING);
-      if (this.connectivityState === ConnectivityState.READY) {
-        setImmediate(resolve);
-      } else {
-        this.once('connect', resolve);
+    if (this.connectivityState === ConnectivityState.READY) {
+      return Promise.resolve();
+    } else if (this.connectivityState === ConnectivityState.SHUTDOWN) {
+      return Promise.reject(new Error('Channel has been shut down'));
+    } else {
+      // In effect, this.connecting is only assigned upon the first attempt to
+      // transition from IDLE to CONNECTING, so this condition could have also
+      // been (connectivityState === IDLE).
+      if (!this.connecting) {
+        this.connecting = new Promise((resolve, reject) => {
+          this.transitionToState([ConnectivityState.IDLE], ConnectivityState.CONNECTING);
+          const onConnect = () => {
+            this.connecting = null;
+            this.removeListener('shutdown', onShutdown);
+            resolve();
+          };
+          const onShutdown = () => {
+            this.connecting = null;
+            this.removeListener('connect', onConnect);
+            reject(new Error('Channel has been shut down'));
+          };
+          this.once('connect', onConnect);
+          this.once('shutdown', onShutdown);
+        });
       }
-    });
+      return this.connecting;
+    }
   }
 
   getConnectivityState(): ConnectivityState {
diff --git a/packages/grpc-js-core/src/client.ts b/packages/grpc-js-core/src/client.ts
index 25fa7bc8..b120fcc7 100644
--- a/packages/grpc-js-core/src/client.ts
+++ b/packages/grpc-js-core/src/client.ts
@@ -42,6 +42,12 @@ export class Client {
         clearTimeout(timer);
       }
       cb(null);
+    }, (err: Error) => {
+      // Rejection occurs if channel is shut down first.
+      if (timer) {
+        clearTimeout(timer);
+      }
+      cb(err);
     });
     if (deadline !== Infinity) {
       let timeout: number;