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https://issues.apache.org/jira/browse/HBASE-22867?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16908960#comment-16908960
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Duo Zhang commented on HBASE-22867:
-----------------------------------
The parallelism is not the thread count. If there are lots of tasks pending,
the number of threads will be much greater than the parallelism...
> The ForkJoinPool in CleanerChore will spawn thousands of threads in our
> cluster with thousands table
> ----------------------------------------------------------------------------------------------------
>
> Key: HBASE-22867
> URL: https://issues.apache.org/jira/browse/HBASE-22867
> Project: HBase
> Issue Type: Bug
> Reporter: Zheng Hu
> Priority: Critical
> Attachments: 31162.stack.1
>
>
> The thousands of spawned threads make the safepoint cost 80+s in our Master
> JVM processs.
> {code}
> 2019-08-15,19:35:35,861 INFO [main-SendThread(zjy-hadoop-prc-zk02.bj:11000)]
> org.apache.zookeeper.ClientCnxn: Client session timed out, have not heard
> from server in 82260ms for sessionid 0x1691332e2d3aae5, closing socket
> connection and at
> tempting reconnect
> {code}
> The stdout from JVM (can see from here there're 9126 threads & sync cost 80+s)
> {code}
> vmop [threads: total initially_running wait_to_block]
> [time: spin block sync cleanup vmop] page_trap_count
> 32358.859: ForceAsyncSafepoint [ 9126 67
> 474 ] [ 1 28 86596 87 101 ] 0
> {code}
> Also we got the jstack:
> {code}
> $ cat 31162.stack.1 | grep 'ForkJoinPool-1-worker' | wc -l
> 8648
> {code}
> It's a dangerous bug, make it as blocker.
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