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From "Izzy Alanis (JIRA)" <j...@apache.org>
Subject [jira] [Created] (AMQ-3326) Synchronization point in RegionBroker adding and removing producers and consumers
Date Wed, 18 May 2011 17:54:47 GMT
Synchronization point in RegionBroker adding and removing producers and consumers
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                 Key: AMQ-3326
                 URL: https://issues.apache.org/jira/browse/AMQ-3326
             Project: ActiveMQ
          Issue Type: Improvement
          Components: Broker
    Affects Versions: 5.5.0, 5.4.2
            Reporter: Izzy Alanis


Synchronization blocks were added to the RegionBroker as a result of AMQ-2821 (automatic removal
of inactive destinations). I believe the author was trying to prevent adding and removing
producers while the inactive destination removal process was running.

This is a major performance bottle neck in use case scenarios where many clients are subscribing
and unsubscribing simultaneously -- specifically, in order to retrieve one and only one message
from a queue using the STOMP protocol (without holding onto a prefetch message) you must subscribe,
retrieve a message and then unsubscribe from the destination. This activity causes lots of
adding and removing of producers and consumers.

I'm still not entirely convinced that the destination removal process needs to be protected
in that manner, but the attached patch uses a ReentrantReadWriteLock to continue to protect
the destination removal process, while still allowing clients to add and remove producers
and consumers concurrently when the destination process is not running.

This patch also relates to AMQ-3070 (where the user was complaining about this same synchronization
block).

I'm attaching patches both for the trunk and for 5.4.2 (which is what I'm still using).

There are other synchronization blocks further down in the code (inside AbstractRegion and
Queue implementations), but in my particular use case, the 2-3x performance enhancement I
get of this patch alone are enough to satisfy my immediate concerns.

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