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https://issues.apache.org/jira/browse/HBASE-21806?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16755559#comment-16755559
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Duo Zhang commented on HBASE-21806:
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One of my goal for introducing AsyncFSWAL is to set a smaller timeout when
writing WAL, so if there are slow DNs we will fail to sync sonn and roll a new
WAL...
But anyway, the proposal here may still be useful, as for example, we can set
the timeout to 5 seconds, and set a 2 seconds threshold, if we haven't got
response after 5 seconds, the sync will fail, if the sync can come back but
still spends more than 2 seconds, we roll a new WAL.
> add an option to roll WAL on very slow syncs
> --------------------------------------------
>
> Key: HBASE-21806
> URL: https://issues.apache.org/jira/browse/HBASE-21806
> Project: HBase
> Issue Type: Bug
> Reporter: Sergey Shelukhin
> Assignee: Sergey Shelukhin
> Priority: Major
> Attachments: HBASE-21806.patch
>
>
> In large heterogeneous clusters sometimes a slow datanode can cause WAL syncs
> to be very slow. In this case, before the bad datanode recovers, or is
> discovered and repaired, it would be helpful to roll WAL on a very slow sync
> to get a new pipeline.
> Otherwise the slow WAL will impact write latency for a long time (slow writes
> result in less writes result in the WAL not being rolled for longer)
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