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From "Richard Yarger (JIRA)" <j...@apache.org>
Subject [jira] Created: (AMQ-1918) AbstractStoreCursor.size gets out of synch with Store size and blocks consumers
Date Thu, 28 Aug 2008 14:30:52 GMT
AbstractStoreCursor.size gets out of synch with Store size and blocks consumers
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                 Key: AMQ-1918
                 URL: https://issues.apache.org/activemq/browse/AMQ-1918
             Project: ActiveMQ
          Issue Type: Bug
          Components: Message Store
    Affects Versions: 5.1.0
            Reporter: Richard Yarger
            Priority: Critical
         Attachments: activemq.xml

In version 5.1.0, we are seeing our queue consumers stop consuming for no reason.
We have a staged queue environment and we occasionally see one queue display negative pending
message counts that hang around -x, rise to -x+n gradually and then fall back to -x abruptly.
The messages are building up and being processed in bunches but its not easy to see because
the counts are negative. We see this behavior in the messages coming out of the system. Outbound
messages come out in bunches and are synchronized with the queue pending count dropping to
-x.

This issue does not happen ALL of the time. It happens about once a week and the only way
to fix it is to bounce the broker. It doesn't happen to the same queue everytime, so it is
not our consuming code.

Although we don't have a reproducible scenario, we have been able to debug the issue in our
test environment.
We traced the problem to the cached store size in the AbstractStoreCursor.
This value becomes 0 or negative and prevents the AbstractStoreCursor from retrieving more
messages from the store. (see AbstractStoreCursor.fillBatch() )
We have seen size value go lower than -1000.
We have also forced it to fix itself by sending in n+1 messages. Once the size goes above
zero, the cached value is refreshed and things work ok again.
Unfortunately, during low volume times, it could be hours before n+1 messages are received,
so our message latency can rise during low volume times.... :(

I have attached our broker config.


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