MessageListener.onMessage is getting called continuously on RabbitMQ with Spring Boot - spring-boot

Question

I have MessageListener.onMessage with a thread sleep. I'm simulating actual processing time the onMessage
method will take by the above mentioned Thread sleep. However what I have noticed is that it is getting called multiple times consecutively for the remaining messages till they get processed by the onMessage method. I see this as an inefficiency.
Actual message count in to queue : 1000
Output of running number for hits
onMessage<<15656
onMessage<<15657
onMessage<<15658
onMessage<<15659
onMessage<<15660
onMessage<<15661
onMessage<<15662
onMessage<<15663
Code block
#Service
class ThreadPooledMessageListener implements MessageListener {
#Autowired
TaskExecutor threadPoolTaskExecutor;
AtomicInteger processedCount = new AtomicInteger();
#Override
public void onMessage(Message message) {
System.out.println("onMessage<<" + processedCount.incrementAndGet());
threadPoolTaskExecutor.execute(new MessageProcessor(message));
}
}
class MessageProcessor implements Runnable {
Message processingMessage;
public MessageProcessor(Message message) {
this.processingMessage = message;
}
#Override
public void run() {
System.out.println("================================"+ Thread.currentThread().getName());
System.out.println(processingMessage);
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
e.printStackTrace();
}
System.out.println("================================");
}
}
What are the possible fixes for this.
As #Gary Russell has pointed out; Issue was that I have used non-spring managed container SimpleMessageListenerContainer in my code. Fixed it with spring managed bean and defined concurrency there. Works as expected.
Fixed code segment
#Bean
public SimpleMessageListenerContainer simpleMessageListenerContainer() {
SimpleMessageListenerContainer container = new SimpleMessageListenerContainer(connectionFactory);
container.setQueues(queue);
container.setMessageListener(threadPooledMessageListener);
container.setConcurrentConsumers(4);
container.start();
return container;
}

Answer 1

>I see this as an inefficiency.
It's not clear what you mean. Since you are handing off the processing of a message to another thread, the listener exits immediately and, of course, the next message is delivered.
This will risk message loss in the event of a failure.
If you are trying to achieve concurrency; it's better to set the container concurrentConsumers property and not do your own thread management in the listener. The container will manage the consumers for you.