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From "Enis Soztutar (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-16721) Concurrency issue in WAL unflushed seqId tracking
Date Wed, 28 Sep 2016 18:51:20 GMT

    [ https://issues.apache.org/jira/browse/HBASE-16721?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15530523#comment-15530523
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Enis Soztutar commented on HBASE-16721:
---------------------------------------

bq. It turned out that the two regions were opened and hosted on other region servers, not
on this region server.
Do you know that whether these regions were opened before on this host, then closed. If it
is, it maybe the same issue. At the time of the log roller and log file cleanup, the region
to force flush is already closed some time ago, but WAL still thinks that there is unflushed
entries from this region. 

> Concurrency issue in WAL unflushed seqId tracking
> -------------------------------------------------
>
>                 Key: HBASE-16721
>                 URL: https://issues.apache.org/jira/browse/HBASE-16721
>             Project: HBase
>          Issue Type: Bug
>            Reporter: Enis Soztutar
>            Assignee: Enis Soztutar
>             Fix For: 2.0.0, 1.3.0, 1.4.0, 1.1.7, 1.2.4
>
>
> I'm inspecting an interesting case where in a production cluster, some regionservers
ends up accumulating hundreds of WAL files, even with force flushes going on due to max logs.
This happened multiple times on the cluster, but not on other clusters. The cluster has periodic
memstore flusher disabled, however, this still does not explain why the force flush of regions
due to max limit is not working. I think the periodic memstore flusher just masks the underlying
problem, which is why we do not see this in other clusters. 
> The problem starts like this: 
> {code}
> 2016-09-21 17:49:18,272 INFO  [regionserver//10.2.0.55:16020.logRoller] wal.FSHLog: Too
many wals: logs=33, maxlogs=32; forcing flush of 1 regions(s): d4cf39dc40ea79f5da4d0cf66d03cb1f
> 2016-09-21 17:49:18,273 WARN  [regionserver//10.2.0.55:16020.logRoller] regionserver.LogRoller:
Failed to schedule flush of d4cf39dc40ea79f5da4d0cf66d03cb1f, region=null, requester=null
> {code}
> then, it continues until the RS is restarted: 
> {code}
> 2016-09-23 17:43:49,356 INFO  [regionserver//10.2.0.55:16020.logRoller] wal.FSHLog: Too
many wals: logs=721, maxlogs=32; forcing flush of 1 regions(s): d4cf39dc40ea79f5da4d0cf66d03cb1f
> 2016-09-23 17:43:49,357 WARN  [regionserver//10.2.0.55:16020.logRoller] regionserver.LogRoller:
Failed to schedule flush of d4cf39dc40ea79f5da4d0cf66d03cb1f, region=null, requester=null
> {code}
> The problem is that region {{d4cf39dc40ea79f5da4d0cf66d03cb1f}} is already split some
time ago, and was able to flush its data and split without any problems. However, the FSHLog
still thinks that there is some unflushed data for this region. 



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