Spring-Boot/AMQP - Limit number of messages processed

Question

I have a spring-boot application using the spring-boot AMQP library.

pom.xml :

<dependency>
   <groupId>org.springframework.boot</groupId>
   <artifactId>spring-boot-starter-amqp</artifactId>
</dependency>

How can I make it process and acknowledge a single message then gracefully exit ?

Can make it exit without acknowledge but cannot seem to work out how to acknowledge the message then exit !

So, you want to ack and process only one message? What if the queue has 100 messages? — Darshan Mehta, Nov 08 '17 at 16:49
@DarshanMehta Yes i want to process a single message and exit even if the queue has 100 messages. — Manse, Nov 08 '17 at 16:51
you can use similar approach as this one : https://stackoverflow.com/questions/41035454/how-to-stop-consuming-messages-with-rabbitlistener. Maybe add an `AtomicInteger` and stop consuming once the count reaches 1? As far as the ack is concerned, Spring will only send an ack if your `listener` method exits gracefully. If you call `stop()`, it won't ack and hence, the message will be available for other users to consume. — Darshan Mehta, Nov 08 '17 at 16:55
@DarshanMehta perhaps i could increment the count at the end of processing the first message and then exit at the start of processing the second should the count reach my specified limit (of 1 in my case) — Manse, Nov 08 '17 at 16:57
Exactly, `incrementAndGet()` is the method you would like to use with `AtomicInteger` and yes, incrementing the count in the end of the method and checking in the beginning is a good idea. I would use `@Value` to configure the number of messages the app needs to read before exiting. — Darshan Mehta, Nov 08 '17 at 17:00
@DarshanMehta Thanks - stick that in an answer and i will mark it as accepted — Manse, Nov 08 '17 at 17:42
I think it would be easier to use the `RabbitTemplate` instead. — Gary Russell, Nov 08 '17 at 18:05

score 4 · Accepted Answer · answered Nov 08 '17 at 18:04

4

You can simply use one of the RabbitTemplate.receive() (or receiveAndConvert()) methods instead of using a listener container.

answered Nov 08 '17 at 18:04

Gary Russell

So this would consumer a message based on request rather then listen for messages - nice idea – Manse Nov 09 '17 at 13:38

score 3 · Answer 2 · answered Nov 09 '17 at 09:38

You can follow the below steps:

Use Spring's RabbitListener as listener (Refer to this SO answer for the complete example)
Declare an AtomicInteger as counter in your listener class
Increment the counter once you listen to the message (i.e. listen method executes without any Exception). Spring will only send an ack when the method executes successfully
If the value of counter is more than 0 (or more than the configured threshold), stop listening by calling stop() method
Use @Value to configure the threshold and use incrementAndget() method to atomically increment the counter

2 Answers2