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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