ActiveMQ: How to handle broker failovers while using temporary queues

Question

On my JMS applications we use temporary queues on Producers to be able to receive replies back from Consumer applications.

I am facing exactly same issue on my end as

Answer 1

There is a broker attribute, org.apache.activemq.broker.BrokerService#cacheTempDestinations that should help in the failover: case. Set that to true in xml configuration, and a temp destination will not be removed immediately when a client disconnects. A fast failover: reconnect will be able to producer and/or consume from the temp queue again.

There is a timer task based on timeBeforePurgeTempDestinations (default 5 seconds) that handles cache removal.

One caveat though, I don't see any tests in activemq-core that make use of that attribute so I can't give you any guarantee on this one.

Answer 2

Temporary queues are created on the broker to which the requestor (producer) in your request-reply scenario connects. They are created from a javax.jms.Session, so on that session disconnecting, either because of client disconnect or broker failure/failover, those queues are permanently gone. None of the other brokers will understand what is meant when one of your consumers attempts to reply to those queues; hence your exception.

This requires an architectural shift in mindset assuming that you want to deal with failover and persist all your messages. Here is a general way that you could attack the problem:

1. Your reply-to headers should refer to a queue specific to the requestor process: e.g. queue:response.<client id>. The client id might be a standard name if you have a limited number of clients, or a UUID if you have a large number of these.
2. The outbound message should set a correlation identifier (simply a sting that lets you associate a request with a response - requestors after all might make more than one request at the same time). This is set in the JMSCorrelationID header, and ought to be copied from the request to the response message.
3. The requestor needs to set up a listener on that queue that will return the message body to the requesting thread based on that correllation id. There is some multithreading code that needs to be written for this, as you'll need to manually manage something like a map of correlation ids to originating threads (via Futures perhaps).

This is a similar approach to that taken by Apache Camel for request-response over messaging.

One thing to be mindful of is that the queue will not go away when the client does, so you should set a time to live on the response message such that it gets deleted from the broker if it has not been consumed, otherwise you will get a backlog of unconsumed messages. You will also need to set up a dead letter queue strategy to automatically discard expired messages.