I have a JMS non-durable topic with multiple subscribers (using ActiveMQ).
Each subscriber is a web application deployed on a separate Tomcat instance. When a message arrives, I want it delivered to all subscribers (somewhat of a distributed cache implementation).
I've noticed that not always the message gets delivered to all subscribers. When looking at the ActiveMQ admin UI I see the list of topic subscribers (as well as the list of connections) constantly changing. E.g. I see 17 subscribers, I refresh the ActiveMQ admin UI, then I see 19 subscribers, I refresh again - I see 18 etc.
What's wrong? I know that all the tomcats are up all the time. My understanding of JMS topics is that if the application is up, the message should always get delivered. Have I misunderstood something? I see no logical reason for this subscriber 'flashing'.
P.S. I'd rather not try durable topics - I don't need the message delivered if the application is not up.