How to poll an AMQP queue using Spring Integration

Question

I have the use case that I need to wait 2 hours before consuming messages from an AMQP (we use Rabbit) queue.

EDIT: To clarify my use case... I need each individual message to wait 2 hours before being read. E.g. Message 1 arrives at 10am and Message 2 arrives at 10:15. I need Message 1 to be read at 12p and Message 2 to be read at 12:15p.

We are using Spring Integration 3.x.

The int-amqp:inbound-channel-adapter is message driven and doesn't have a polling option from what I can find.

A couple things I've thought of:

• Set auto-startup to false and manually start the inbound channel adapter using a quartz job.
• Create my own custom SimpleMessageListenerContainer that is based on polling (not sure how easy this would be)
• Configure a "delay queue" in rabbitmq using this method: How to create a delayed queue in RabbitMQ?
• EDIT: add 4th option: Use delayer to delay each message for 2 hours: http://docs.spring.io/spring-integration/docs/3.0.2.RELEASE/reference/html/messaging-endpoints-chapter.html#delayer

Any suggestions?

Answer 1

FYI, how I solved the issue. (Used solution #3).

<rabbit:queue name="delayQueue" durable="true">
  <rabbit:queue-arguments>
    <entry key="x-message-ttl">
       <value type="java.lang.Long">7200000</
     </entry>
     <entry key="x-dead-letter-exchange" value="finalDestinationTopic"/>
     <entry key="x-dead-letter-routing-key" value="finalDestinationQueue"/>
  </rabbit:queue-arguments>
</rabbit:queue>

<rabbit:topic-exchange name="finalDestinationTopic">
  <rabbit:bindings>
    <rabbit:binding queue="finalDestinationQueue" pattern="finalDestinationQueue"/>
  </rabbit:bindings>
</rabbit:topic-exchange>

Answer 2

Another trick is about to use PollableAmqpChannel:

<int-amqp:channel id="myQueueName" message-driven="false"/>

and provide the <poller> for the subscriber to that channel.

There is no reason to send messages to that channel (because you will poll messages from Rabbit Queue) and, right, it looks like anti-pattern, but it is a hook how to avoid any workarounds with direct RabbitTemplate usage via SpEL.

UPDATE

<delayer> can help you, but it depends of your requirements. If you don't want to poll messages from RabbitMQ, you should use the workaround above. But if you just don't want to process message until some time is elapsed, you can just 'delay' it for that time.

Don't forget to add persistent message-store to avoid losing messages during that period and unexpected application failure.

Answer 3

We don't currently have a polling inbound adapter. #1 is easy. For #2, the simplest would be to use a RabbitTemplate and invoke receive() from an inbound-channel-adapter in a POJO.

I would go with #1; you don't need quartz, you can use a simple Spring scheduled task and a control bus to start the adapter.