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From "Lei (Eddy) Xu (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (HDFS-12412) Change ErasureCodingWorker.stripedReadPool to cached thread pool
Date Wed, 13 Sep 2017 01:17:00 GMT

     [ https://issues.apache.org/jira/browse/HDFS-12412?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Lei (Eddy) Xu updated HDFS-12412:
---------------------------------
       Resolution: Fixed
    Fix Version/s: 3.0.0-beta1
     Release Note: Changed {{stripedReadPool}} to unbounded cachedThreadPool.  User should
combine {{dfs.datanode.ec.reconstruction.stripedblock.threads}} and {{dfs.namenode.replication.max-streams}}
to tune recovery performance.
           Status: Resolved  (was: Patch Available)

Thanks for the reviews, [~andrew.wang]

Ran {{TestReconstructStripedFile,TestReadStripedFileWithMissingBlocks}} locally and passes.
The rest seem not relevant. Filed HDFS-12439 for TestReconstructStripedFile.

Committed to {{trunk}}. 

> 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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