[ https://issues.apache.org/jira/browse/HBASE-7295?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13528338#comment-13528338 ]
Varun Sharma commented on HBASE-7295: ------------------------------------- Hi Lars, Interesting, I did not know all this :) I think correctness is more important. In fact when I completely did away with the synchronized block, I was entering some weird edge cases where an incorrect connection was being returned (like a connection from pool for server A when the call needs to go to server B) - those went away after getting the synchronized block back. So we can make this volatile - it should still incur less overhead since there is no locking overhead at least. Lemme prep another set of patches with volatile. Thanks Varun > 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-trunk.txt, 7295-trunk.txt, 7295-trunk-v2.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. -- This message is automatically generated by JIRA. If you think it was sent incorrectly, please contact your JIRA administrators For more information on JIRA, see: http://www.atlassian.com/software/jira