Spring Integration Multiple consumers not processing concurrently

Question

I am using Spring Integration with ActiveMQ. I defined a DefaultMessageListenerContainer with maxConcurrentConsumers = 5. It is referenced in a . After an int-xml:validating-filter and an int-xml:unmarshalling-transformer, I defined a queue channel actionInstructionTransformed. And I have got a poller for this queue channel. When I start my application, in the ActiveMQ console, I can see that a connection is created and inside five sessions.

Now, I have got a @MessageEndpoint with a method annotated

@ServiceActivator(inputChannel = "actionInstructionTransformed", poller = @Poller(value = "customPoller")). 

I have got a log statement at the method entrance. Processing of each message is long (several minutes). In my logs, I can see that thread-1 starts the processing and then I can only see thread-1 outputs. Only when thread-1 has finished processing 1 message, I can see thread-2 starts processing the next message, etc. I do NOT have any synchronized block inside my class annotated @MessageEndpoint . I have not managed to get thread-1 , thread-2 , etc process messages concurrently.

Has anybody experienced something similar?

Answer 1

Look, you say:

After an int-xml:validating-filter and an int-xml:unmarshalling-transformer, I defined a queue channel actionInstructionTransformed.

Now let's go to the QueueChannel and PollingConsumer definitions !

On the other hand, a channel adapter connected to a channel that implements the org.springframework.messaging.PollableChannel interface (eg a QueueChannel) will produce an instance of PollingConsumer.

And pay attention that @Poller ( PollerMetadata ) has taskExecutor option.

By default the TaskScedhuler ask QueueChannel for data periodically according to the trigger configuration. If that is PeriodicTrigger with default options like fixedRate = false , the next poll really happens after the previous one. That's why you see only one Thread.

So, try to configure taskExecutor and your messages from that queue will go in parallel.

The concurrency on the DefaultMessageListenerContainer does not have effect. Because in the end you place all those messages to the QueueChannel . And here a new Threading model starts to work based on the @Poller configuration.