[jira] [Updated] (AMQCPP-675) Consumer performance issues with many topics

["Rob Ambalu (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/AMQCPP-675?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Rob Ambalu updated AMQCPP-675:
------------------------------
    Attachment: 0001-consumer-performance-improvement-use-hashmap-over-li.patch

> 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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