使用 Spring Boot 在 RabbitMQ 上不断调用 MessageListener.onMessage

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.