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From "Izzy Alanis (JIRA)" <>
Subject [jira] [Updated] (AMQ-3326) Synchronization point in RegionBroker adding and removing producers and consumers
Date Wed, 18 May 2011 18:00:48 GMT


Izzy Alanis updated AMQ-3326:

    Attachment: RegionBroker-542.patch

> Synchronization point in RegionBroker adding and removing producers and consumers
> ---------------------------------------------------------------------------------
>                 Key: AMQ-3326
>                 URL:
>             Project: ActiveMQ
>          Issue Type: Improvement
>          Components: Broker
>    Affects Versions: 5.4.2, 5.5.0
>            Reporter: Izzy Alanis
>         Attachments: RegionBroker-542.patch, RegionBroker-trunk.patch
> 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
> 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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