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https://issues.apache.org/jira/browse/HBASE-16721?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15539206#comment-15539206
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Enis Soztutar commented on HBASE-16721:
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bq. Why AutoCloseable instead of Closeable?
Yeah, it should be Closeable instead. Let me push an addendum.
> Concurrency issue in WAL unflushed seqId tracking
> -------------------------------------------------
>
> Key: HBASE-16721
> URL: https://issues.apache.org/jira/browse/HBASE-16721
> Project: HBase
> Issue Type: Bug
> Components: wal
> Affects Versions: 1.0.0, 1.1.0, 1.2.0
> Reporter: Enis Soztutar
> Assignee: Enis Soztutar
> Priority: Critical
> Fix For: 2.0.0, 1.3.0, 1.4.0, 1.2.4, 1.1.8
>
> Attachments: hbase-16721_v1.branch-1.patch,
> hbase-16721_v2.branch-1.patch, hbase-16721_v2.master.patch
>
>
> 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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