Spring AMQP 侦听器事务的目的是什么

Question

I'm trying to understand how transaction works in Spring AMQP. Reading the docs:https://docs.spring.io/spring-amqp/reference/html/#transactions , I know the purpose for enabling transaction in publisher (Best Effort One Phase Commit pattern) but I have no idea why it could be necessary in MessageListener?

Let's take an example:

acknowledgeMode=AUTO

1. Consume message using @RabbitListener
2. Insert data into database
3. Publish message using rabbitTemplate

According to docs: https://docs.spring.io/spring-amqp/reference/html/#acknowledgeMode , if acknowledgeMode is set to AUTO then if any next operation fails, listener will fail too and message will be returned to queue.

Another question is whats the difference between local transaction and external transaction in that case (setting container.setTransactionManager(transactionManager()); or not)?

I would appreciate some clarification:)

Answer 1

Enable transactions in the listener so that any/all downstream RabbitTemplate operations participate in the same transaction.

If there is a failure, the container will rollback the transaction (removing the publishes), nack the message (or messages if batch size is greater than one) and then commit the nacks so the message(s) will be redelivered.

When using an external transaction manager (such as JDBC), the container will synchronize the AMQP transaction with the external transaction.

Downstream templates participate in the transaction regardless of whether it is local (AMQP only) or synchronized.