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https://issues.apache.org/jira/browse/HBASE-22867?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16912869#comment-16912869
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Zheng Hu commented on HBASE-22867:
----------------------------------
Attached two jstack files: 191318.stack and 191318.stack.1 .
I got the 191318.stack file firstly, after few seconds, caught the
191318.stack.1 files. In the first file, we can clearly see that there are 6
threads in dir-scan-pool which was blocked and waiting for the
SnapshotHFileCleaner#getDeletableFiles.
{code}
"dir-scan-pool4-thread-8" #18765 daemon prio=5 os_prio=0 tid=0x00007f4a20009c60
nid=0x6576 waiting for monitor entry [0x00007f48a6191000]
java.lang.Thread.State: BLOCKED (on object monitor)
at
org.apache.hadoop.hbase.master.snapshot.SnapshotHFileCleaner.getDeletableFiles(SnapshotHFileCleaner.java:68)
- waiting to lock <0x000000034411dc88> (a
org.apache.hadoop.hbase.master.snapshot.SnapshotHFileCleaner)
at
org.apache.hadoop.hbase.master.cleaner.CleanerChore.checkAndDeleteFiles(CleanerChore.java:295)
at
org.apache.hadoop.hbase.master.cleaner.CleanerChore.lambda$traverseAndDelete$1(CleanerChore.java:405)
at
org.apache.hadoop.hbase.master.cleaner.CleanerChore$$Lambda$187/1141106127.act(Unknown
Source)
at
org.apache.hadoop.hbase.master.cleaner.CleanerChore.deleteAction(CleanerChore.java:460)
at
org.apache.hadoop.hbase.master.cleaner.CleanerChore.traverseAndDelete(CleanerChore.java:405)
at
org.apache.hadoop.hbase.master.cleaner.CleanerChore.lambda$null$2(CleanerChore.java:414)
at
org.apache.hadoop.hbase.master.cleaner.CleanerChore$$Lambda$185/2070209024.run(Unknown
Source)
at
java.util.concurrent.CompletableFuture$AsyncRun.run(CompletableFuture.java:1626)
at
java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
at
java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
at java.lang.Thread.run(Thread.java:748)
Locked ownable synchronizers:
- <0x000000038a476bf8> (a
java.util.concurrent.ThreadPoolExecutor$Worker)
{code}
In the second file, the threads has finished all the work and are waiting for
the new task. That means the cleaner won't be blocked now, it's seems good.
> 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
> Assignee: Zheng Hu
> Priority: Critical
> Attachments: 191318.stack, 191318.stack.1, 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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