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From Shyam Santhanam <>
Subject Re: Problems with Virtual Topics
Date Thu, 01 Apr 2010 14:04:45 GMT

There are a few more observations I've made while trying to debug this. We've
noticed that sometimes the messages received from the consumer queues have
JMSDestination set to the VirtualTopic name, and at other times they have
the consumer queue name. As shown earlier, I do have the
excludedDestinations clause necessary to exclude forwarding to the queues.
Is this still to be expected?

Also, looking in JMX at the VirtualTopic's topic MBeans, I've noticed that
the topics themselves have consumers in addition to the queue. Are these
consumers created internally by the broker to enable forwarding, or could
this indicate a problem? Further, there are far many more consumers for the
topics. For example, when testing with 2 nodes: Although I have only one
consumer queue attached to the topic, and one consumer  to this topic on
each node, I notice that the VirtualTopic itself shows 6 consumers. Where
are these consumers coming from?

Another observation when looking at the MBeans: the QueueSize of the topics
appears to increase steadily over time. When I try to browse the contents of
the topic, I often find that there are some residual messages (usually far
fewer messages than indicated by the QueueSize statistic, but > 0
nonetheless). Again, this doesn't gel with my understanding. I thought that
the topics themselves are "virtual" which should imply that they don't have
a persistent cache of messages anywhere? Are the virtual topics themselves
also persisted? If so, when do messages in the topic get evacuated?

If someone familiar with this area could answer these questions, it could
really help us make some important decisions about how, and whether, to use
virtual topics to implement our requirements. Has someone used them
effectively in a network-of-brokers scenario? If so, can you share the
specifics of your configuration?

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