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https://issues.apache.org/jira/browse/HDFS-12412?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16184501#comment-16184501
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Andrew Wang commented on HDFS-12412:
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I've cherry-picked this to branch-3.0 for beta1.
> Change ErasureCodingWorker.stripedReadPool to cached thread pool
> ----------------------------------------------------------------
>
> Key: HDFS-12412
> URL: https://issues.apache.org/jira/browse/HDFS-12412
> Project: Hadoop HDFS
> Issue Type: Improvement
> Components: erasure-coding
> Affects Versions: 3.0.0-alpha3
> Reporter: Lei (Eddy) Xu
> Assignee: Lei (Eddy) Xu
> Labels: hdfs-ec-3.0-nice-to-have
> Fix For: 3.0.0-beta1
>
> Attachments: HDFS-12412.00.patch, HDFS-12412.01.patch
>
>
> In {{ErasureCodingWorker}}, it uses {{stripedReconstructionPool}} to schedule
> the EC recovery tasks, while uses {{stripedReadPool}} for the reader threads
> in each recovery task. We only need one of them to throttle the speed of
> recovery process, because each EC recovery task has a fix number of source
> readers (i.e., 3 for RS(3,2)). And because of the findings in HDFS-12044, the
> speed of EC recovery can be throttled by {{strippedReconstructionPool}} with
> {{xmitsInProgress}}.
> Moreover, keeping {{stripedReadPool}} makes customer difficult to understand
> and calculate the right balance between
> {{dfs.datanode.ec.reconstruction.stripedread.threads}},
> {{dfs.datanode.ec.reconstruction.stripedblock.threads.size}} and
> {{maxReplicationStreams}}. For example, a small {{stripread.threads}}
> (comparing to which {{reconstruction.threads.size}} implies), will
> unnecessarily limit the speed of recovery, which leads to larger MTTR.
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