Do not block while waiting for previous message to be confirmed

src/ChannelWrapper.js

@@ -163,6 +163,9 @@ export default class ChannelWrapper extends EventEmitter {
         // Place to store queued messages.
         this._messages = [];
 
+        // Place to store published, but not yet confirmed messages
+        this._unconfirmedMessages = [];
+
         // True if the "worker" is busy sending messages.  False if we need to
         // start the worker to get stuff done.
         this._working = false;
@@ -231,6 +234,12 @@ export default class ChannelWrapper extends EventEmitter {
                 // Can happen if channel closes while we're setting up.
                 return;
             }
+            if (this._unconfirmedMessages.length > 0) {
+                // requeu any messages that were left unconfirmed when connection was lost
+                while (this._unconfirmedMessages.length) {
+                    this._messages.push(this._unconfirmedMessages.shift());
+                }
+            }
 
             // Since we just connected, publish any queued messages
             this._startWorker();
@@ -278,6 +287,10 @@ export default class ChannelWrapper extends EventEmitter {
                 // Reject any unsent messages.
                 this._messages.forEach(message => message.reject(new Error('Channel closed')));
             }
+            if(this._unconfirmedMessages.length !== 0) {
+                // Reject any unconfirmed messages.
+                this._unconfirmedMessages.forEach(message => message.reject(new Error('Channel closed')));
+            }
 
             this._connectionManager.removeListener('connect', this._onConnect);
             this._connectionManager.removeListener('disconnect', this._onDisconnect);
@@ -311,7 +324,8 @@ export default class ChannelWrapper extends EventEmitter {
         }
 
         const channel = this._channel;
-        const message = this._messages[0];
+        const message = this._messages.shift();
+        this._unconfirmedMessages.push(message);
 
         Promise.resolve()
         .then(() => {
@@ -348,29 +362,27 @@ export default class ChannelWrapper extends EventEmitter {
                 }
             })();
 
+            // Send some more!
+            this._publishQueuedMessages(workerNumber);
+
             return sendPromise;
         })
         .then(
             result => {
-                this._messages.shift();
+                this._unconfirmedMessages.shift();
                 message.resolve(result);
-
-                // Send some more!
-                this._publishQueuedMessages(workerNumber);
             },
 
             err => {
                 if(!this._channel) {
                     // Tried to write to a closed channel.  Leave the message in the queue and we'll try again when we
                     // reconnect.
+                    this._messages.unshift(this._unconfirmedMessages.shift());
                 } else {
                     // Something went wrong trying to send this message - could be JSON.stringify failed, could be the
                     // broker rejected the message.  Either way, reject it back
-                    this._messages.shift();
+                    this._unconfirmedMessages.shift();
                     message.reject(err);
-
-                    // Send some more!
-                    this._publishQueuedMessages(workerNumber);
                 }
             }
         )

test/ChannelWrapperTest.js

@@ -589,4 +589,27 @@ describe('ChannelWrapper', function() {
                 return p1;
             }).then(() => expect(publishCalls).to.equal(2));
     });
-});
+
+    it('should publish enqued messages to the underlying channel without waiting for confirms', function() {
+        connectionManager.simulateConnect();
+        let p1, p2;
+        const channelWrapper = new ChannelWrapper(connectionManager, {
+            setup(channel) {
+                channel.publish = sinon.stub();
+                return Promise.resolve();
+            }
+        });
+
+        return channelWrapper.waitForConnect()
+            .then(() => {
+                p1 = channelWrapper.publish('exchange', 'routingKey', 'msg:1');
+                p2 = channelWrapper.publish('exchange', 'routingKey', 'msg:2');
+                return promiseTools.delay(10);
+            }).then(() => {
+                const channel = channelWrapper._channel;
+                expect(channel.publish.calledTwice).to.be.true;
+                expect(p1).to.not.be.fulfilled;
+                expect(p2).to.not.be.fulfilled;
+            });
+    });
+});