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https://issues.apache.org/jira/browse/AMQ-7102?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16897074#comment-16897074
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Graeme Moss edited comment on AMQ-7102 at 7/31/19 11:41 AM:
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This is a good fix. Thanks. Unfortunately we are using 5.15.6 and the
possibility of an upgrade seems difficult for various reasons.
However, why is this collection a CopyOnWriteArraySet? It seems that most of
the time you will be wanting to modify this set, and modifications seem
particularly slow for a CopyOnWriteArraySet. It locks the set entirely whilst
it (potentially) searches all elements linearly for the element you are
adding/removing and then copies them all. Would it not be better to have a
ConcurrentHashSet, like the ConcurrentHashMap fields that key on ObjectName in
ManagedRegionBroker?
We have a broker running with 600k elements in registeredMBeans and we severe
performance issues when adding/removing many subscribers at once (e.g.
something that adds subscribers usually takes 2 mins but when many other
subscribers are added and removed at the same time it takes 45 mins, over 20
times slower). Looking at stackdumps of the broker I see many (40+) threads
BLOCKED on trying to get a lock on the underlying CopyOnWriteArrayList whilst
trying to add/remove subscribers.
was (Author: graeme_moss):
This is a good fix. Thanks. Unfortunately we are using 5.15.6 and the
possibility of an upgrade seems difficult for various reasons.
However, why is this collection a CopyOnWriteArraySet? It seems that most of
the time you will be wanting to modify this set, and modifications seem
particularly slow for a CopyOnWriteArraySet. It locks the set entirely whilst
it searches all elements linearly for the element you are adding/removing.
Would it not be better to have a ConcurrentHashSet, like the ConcurrentHashMap
fields that key on ObjectName in ManagedRegionBroker?
We have a broker running with 600k elements in registeredMBeans and we severe
performance issues when adding/removing many subscribers at once (e.g.
something that adds subscribers usually takes 2 mins but when many other
subscribers are added and removed at the same time it takes 45 mins, over 20
times slower). Looking at stackdumps of the broker I see many (40+) threads
BLOCKED on trying to get a lock on the underlying CopyOnWriteArrayList whilst
trying to add/remove subscribers.
> managementContext suppressMBean filters registration but still tracks objects
> as registered in error
> ----------------------------------------------------------------------------------------------------
>
> Key: AMQ-7102
> URL: https://issues.apache.org/jira/browse/AMQ-7102
> Project: ActiveMQ
> Issue Type: Improvement
> Components: JMX
> Affects Versions: 5.15.0
> Reporter: Gary Tully
> Assignee: Gary Tully
> Priority: Major
> Fix For: 5.16.0
>
>
> The suppressMbean feature could be better is we don't unnecessarily track the
> suppressed mbean registrations in out copy on write set.
> Under load, the additional work on add/remove this can be a significant
> burden.
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