使用Akka持久邮箱进行事务性消息处理

Question

I have a Java/Akka application that is integrated with a persistent JMS ( ActiveMQ ) queue.

The PersistentQueue wraps a JMS/ActiveMQ queue containing batch jobs. Messages are received in a transaction so that if the server goes down in the middle of job execution then the job will be preserved on restart. If the job completes successfully or is cancelled by the user then this transaction is committed to permanently remove the message, and if the job fails then the transaction is rolled back (putting the message on the front of the queue) if the job has executed fewer than MAX_RETRY times.

The BatchManager is the interface with the REST controller. It is only able to execute one batch job at a time due to limitations imposed by the stored procedures called during job execution. The BatchManager receives jobs from the controller and sends them to the PersistentQueue to be put in the JMS queue, and then polls the PersistentQueue for a new job when a job is enqueued (unless another job is executing) or when a job completes.

I would like to remove the JMS queue and all of the complication of dealing with its JMSExceptions and replace it with a durable mailbox for the BatchManager . The problem is that I don't know how I can replicate JMS transactions with a durable mailbox - my understanding is that if the server goes down during job execution then that message is lost forever (as opposed to being put back on the queue for the JMS queue).

Is there a way to effect transactional message processing with an Akka durable mailbox, so that a message won't be lost if the server goes down while it is being executed?

Answer 1

Akka documentation says:

A durable mailbox is like any other mailbox not likely to be transactional. It's possible if the actor crashes after receiving a message, but before completing processing of it, that the message could be lost.

But there is also another type of mailbox - Mailbox with Explicit Acknowledgement (aka PeekMailbox). Here you can find usage example. And here is the implementation source code.

I think you can achieve your goal by implementing custom durable mailbox which extends some of the existing implementations and augments it with the PeekMailbox capabilities.

Answer 2

You could achieve this using a PersistentActor to keep track of posted and completed jobs.

The "distributed workers" activator template contains such a work unit managing actor. (As well as dynamic worker registration and clustering but it might still be worth looking at even if those aren't of interest to you).

Scala version of the template and Java version of the template