PubSubInboundChannelAdapter stops to receive messages after 4th message

Question

I\'ve created simplified example which reproduces my real problem.

My example accepts from google pub/sub, logs it and send ack back to the Pub/Sub

Answer 1

You problem is here:

.gateway(acknowledgementFlow);

It means request-reply and we can't guess that your acknowledgementFlow is one-way flow. I see that by your MyPubSubAckHandler implementation which returns void for its handleMessage() implementation. This way a gateway waits for reply, but the real sub-flow will never return any result. Therefore awaiting for reply threads are stuck and eventually your application fail.

One of the solution is to make a GatewayEndpointSpec.replyTimeout() as 0. So, your void sub-flow won't block a main flow for potential reply.

Another way just don't use gateway(), but that sub-flow content directly in the main flow. It really doesn't look like you expect some reply so this should work for you:

  return flow -> flow.channel(bucketNotificationChannel())
            .handle(handler)
            .log(INFO, "Handler finished", m -> {
                return "got" + m;
            })
            .log(DEBUG, "acknowledgementFlow", m -> "Handling acknowledgement for message: " + m)
            .handle(pubSubAckHandler);