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https://issues.apache.org/jira/browse/AMQCPP-675?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17329948#comment-17329948
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Rob Ambalu commented on AMQCPP-675:
-----------------------------------
added diff as a patch file, added one more simple perf improvement, keep
dispatchers in ActiveMQConnection by HashMap rather than (ordered) StlMap.
> Consumer performance issues with many topics
> --------------------------------------------
>
> Key: AMQCPP-675
> URL: https://issues.apache.org/jira/browse/AMQCPP-675
> Project: ActiveMQ C++ Client
> Issue Type: Improvement
> Reporter: Rob Ambalu
> Assignee: Timothy A. Bish
> Priority: Major
> Attachments:
> 0001-consumer-performance-improvement-use-hashmap-over-li.patch, diff.txt
>
>
> activemq-cpp has a performance issue when subscribing to many topics. When I
> try to subscribe to market data by ticker, with 1 topic per ticker, it starts
> to bog down as I add more Consumers. Digging into it, I see the issue is in
> how consumers are managed in ActiveMQSessionKernel.cpp. It maintains all
> consumers in a linked list, and then for *every message* that is received, it
> does a linear O(n) scan to find the matching consumer to call back into.
> My application has close to 10k topics subscribed, every message does up to
> 10k scan. This is completely unusable.
> The fix is simple, maintain consumers by HashMap not a LinkedList. I dont
> have access to create a pull-request in github, but I already have the diffs
> and will attach it to this PR.
>
> Some notes:
> * adding an identical consumer will silently fail, but this is the same
> behavior as it is today ( duplicates will add to the LinkedList of consumers,
> but upon lookup only the first one will be returned... )
> * Added slight optim to ConsumerId::getHashCode() because it was too
> unnecessarily inefficient to bare
> * I removed the ActiveMQSessionKernel::deliverAcks() because its not used
> anywhere, and it does a full iteration so I want to make sure it never gets
> used
> * I tested this on my use case and my application can easily keep up without
> issue now
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