pr comment

pongad · pongad · commit ce4799029827 · 2017-06-06T12:22:29.000+10:00
diff --git a/google-cloud-pubsub/src/main/java/com/google/cloud/pubsub/spi/v1/PollingSubscriberConnection.java b/google-cloud-pubsub/src/main/java/com/google/cloud/pubsub/spi/v1/PollingSubscriberConnection.java
@@ -132,13 +132,32 @@ private void pullMessages(final Duration backoff) {
             PullRequest.newBuilder()
                 .setSubscription(subscription)
                 .setMaxMessages(maxDesiredPulledMessages)
+                .setReturnImmediately(false)
                 .build());
 
     Futures.addCallback(
         pullResult,
         new FutureCallback<PullResponse>() {
           @Override
           public void onSuccess(PullResponse pullResponse) {
+            if (pullResponse.getReceivedMessagesCount() == 0) {
+              // No messages in response, possibly caught up in backlog, we backoff to avoid
+              // slamming the server.
+              pollingExecutor.schedule(
+                  new Runnable() {
+                    @Override
+                    public void run() {
+                      Duration newBackoff = backoff.multipliedBy(2);
+                      if (newBackoff.compareTo(MAX_BACKOFF) > 0) {
+                        newBackoff = MAX_BACKOFF;
+                      }
+                      pullMessages(newBackoff);
+                    }
+                  },
+                  backoff.toMillis(),
+                  TimeUnit.MILLISECONDS);
+              return;
+            }
             messageDispatcher.processReceivedMessages(
                 pullResponse.getReceivedMessagesList(),
                 new Runnable() {
