PrefetchSubscription may not wake up if messages delivered in transaction

• Key: AMQ-1632
• Type: Bug
• Status: Closed
• Resolution: Fixed
• Priority: Major
• Assignee: David Jencks
• Reporter: David Jencks
• Component/s: Broker
• Affects Version/s: 4.1.1
• Fix Version/s: 4.1.2

Description

we noticed mdbs w/transaction on don't work if the prefetch size is less than the number of sessions for the mdb. There's an error in calculating the prefetchExtension in afterCommit and there's no notification that it might be time to send more messages. Apparently if the prefetch size is large enough one of the earlier acks triggers delivery of the next batch.

There are also a bunch of synchronization errors in some classes...

Comments

[David Jencks]

Fixed in rev 640336, branches 4.1. The actual fix is in activemq-core/src/main/java/org/apache/activemq/broker/region/PrefetchSubscription.java, other files contain thread-safety improvements. Leaving open till I can check trunk for similar problems.

[David Jencks]

I talked with Hiram a bit and we decided that the real problem was that prefetchSize was being calculated wrong. MDBs instances for an activation spec all share a single multithreaded consumer. So the prefetch size ought to be maxMessagesPerSession * maxSessions, so each mdb gets a chance at maxMessagesPerSession. Previously prefetchSize = maxMessagesPerSession which resulted in some mdbs never getting a chance to process anything if maxMessagesPerSession < maxSessions.

Still haven't looked at trunk.

[David Jencks]

Still a good idea to look at trunk.