Enable long polling in QueueMessagingTemplate

[budaimartin]

Background

I'm using QueueMessagingTemplate to send and receive messages to/from an SQS queue. Receive happens in an infinite loop that regularly polls the queue. However, when there are no messages on the queue, a large amount of empty receives happens which increases costs. I set ReceiveMessageWaitTimeSeconds on the queue in order to benefit from the long polling funcitonality of SQS, but the situation didn't get better.

I realized that QueueMessagingTemplate::receive delegates to QueueMessageChannel::receive without a parameter and then a hardcoded 0 value is then set in the ReceiveMessageRequest here: https://github.com/spring-cloud/spring-cloud-aws/blob/master/spring-cloud-aws-messaging/src/main/java/org/springframework/cloud/aws/messaging/core/QueueMessageChannel.java#L220-L241. This overwrites the default setting and makes it impossible to use long polling.

Suggestion

Please consider the following to make long polling possible:

• Make the default timeout configurable instead of hard-coded 0
• If timeout is not given, do not set it in the request (this way, the one set in the SQS queue itself will be used)

Alternatives considered

I tried using @SqsListener where ReceiveMessageWaitTimeSeconds could be set via SimpleMessageListenerContainerFactory, but the architecture of my application would require dynamic creation of the queue listener and preferably outside of Spring ApplicationContext. A similar flexible solution could be provided for QueueMessagingTemplate.

[maciejwalkowiak]

Thanks for reporting and suggestions!