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https://issues.apache.org/jira/browse/HBASE-7295?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13536297#comment-13536297
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Lars Hofhansl commented on HBASE-7295:
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Yeah, maybe use ConcurrentHashMap.putIfAbsent (I think one of your patches had
that). If you find the Connection is in there already at that point just close
the newly created one.
In the end I am somewhat skeptical that this is even an issue. Do you have a
matching number of handlers threads at the regionservers?
(hbase.regionserver.handler.count)
> Contention in HBaseClient.getConnection
> ---------------------------------------
>
> Key: HBASE-7295
> URL: https://issues.apache.org/jira/browse/HBASE-7295
> Project: HBase
> Issue Type: Improvement
> Affects Versions: 0.94.3
> Reporter: Varun Sharma
> Assignee: Varun Sharma
> Fix For: 0.96.0, 0.94.4
>
> Attachments: 7295-0.94.txt, 7295-0.94-v2.txt, 7295-0.94-v3.txt,
> 7295-0.94-v4.txt, 7295-0.94-v5.txt, 7295-trunk.txt, 7295-trunk.txt,
> 7295-trunk-v2.txt, 7295-trunk-v3.txt, 7295-trunk-v3.txt
>
>
> HBaseClient.getConnection() synchronizes on the connections object. We found
> severe contention on a thrift gateway which was fanning out roughly 3000+
> calls per second to hbase region servers. The thrift gateway had 2000+
> threads for handling incoming connections. Threads were blocked on the
> syncrhonized block - we set ipc.pool.size to 200. Since we are using
> RoundRobin/ThreadLocal pool only - its not necessary to synchronize on
> connections - it might lead to cases where we might go slightly over the
> ipc.max.pool.size() but the additional connections would timeout after
> maxIdleTime - underlying PoolMap connections object is thread safe.
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