Multiple processes servicing a single subscription causes MQRC_SUBSCRIPTION_IN_USE

Question

I have a TIBCO BusinessWorks process that is publishing to a JMS topic -- lets call it TOPIC.A -- there is one process that is subscribing to that topic with a name SUBSCRIBE.A.

The problem I have is that the first server that starts listening to SUBSCRIBE.A hooks in fine. The other 3 servers, running the exact same process get an error of "WebSphere MQ call failed with compcode '2' ('MQCC_FAILED') reason '2429' ('MQRC_SUBSCRIPTION_IN_USE')"

This can't be reasonable behavior for enterprise software, and I know WebsphereMQ, JMS and TIBCO Businessworks all scale well, so I must be missing something. I only want each event processed once, but a single box just isn't going to do it, both for fail-over reasons and shear volume reasons.

What do I have to do to let all 4 servers in the cluster to service the subscription SUBSCRIBE.A?

Answer 1

I agree it does not seem like reasonable behavior for enterprise software - but this restriction is imposed by the JMS specification. The JMS 1.1 spec, section 6.66.1 says "Only one session at a time can have a TopicSubscriber for a particular durable subscription".

That said, WebSphere MQ does provide a vendor-specific option that allows you to do what you want: see the CLONESUPP Connection Factory property. This is documented in the Infocenter at the CLONESUPP properties page.

While it's specific to MQ, if you specify this using administered objects you code will not need to use any vendor-specific methods.

Answer 2

The reason for MQRC 2429 is because all of your 4 subscribers are using the same client ID and all are trying to use the same durable subscription. When a subscriber is already actively listening on a durable subscription, no other subscribers can listen on the same. If you want all subscribers to listen concurrently, then have separate client ids for each of your subscribers.

But you must note that all subscribers will get a copy of the same message published by a publisher (TIBCO BusinessWorks in your case). So if all subscribers are active, all will process the event.

For fail-over you can look at using WebSphere MQ Multi-instance queue manager feature or any other HA solutions. For load sharing you can look at WebSphere MQ clustering feature.