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From "Hadoop QA (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-12044) Mismatch between BlockManager#maxReplicatioStreams and ErasureCodingWorker.stripedReconstructionPool pool size causes slow and burst recovery.
Date Wed, 28 Jun 2017 21:59:00 GMT

    [ https://issues.apache.org/jira/browse/HDFS-12044?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16067315#comment-16067315
] 

Hadoop QA commented on HDFS-12044:
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| (x) *{color:red}-1 overall{color}* |
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|| Vote || Subsystem || Runtime || Comment ||
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Docker mode activated. {color} |
| {color:red}-1{color} | {color:red} patch {color} | {color:red}  0m  5s{color} | {color:red}
HDFS-12044 does not apply to trunk. Rebase required? Wrong Branch? See https://wiki.apache.org/hadoop/HowToContribute
for help. {color} |
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|| Subsystem || Report/Notes ||
| JIRA Issue | HDFS-12044 |
| JIRA Patch URL | https://issues.apache.org/jira/secure/attachment/12874965/HDFS-12044.02.patch
|
| Console output | https://builds.apache.org/job/PreCommit-HDFS-Build/20083/console |
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> Mismatch between BlockManager#maxReplicatioStreams and ErasureCodingWorker.stripedReconstructionPool
pool size causes slow and burst recovery. 
> -----------------------------------------------------------------------------------------------------------------------------------------------
>
>                 Key: HDFS-12044
>                 URL: https://issues.apache.org/jira/browse/HDFS-12044
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: erasure-coding
>    Affects Versions: 3.0.0-alpha3
>            Reporter: Lei (Eddy) Xu
>            Assignee: Lei (Eddy) Xu
>         Attachments: HDFS-12044.00.patch, HDFS-12044.01.patch, HDFS-12044.02.patch
>
>
> {{ErasureCodingWorker#stripedReconstructionPool}} is with {{corePoolSize=2}} and {{maxPoolSize=8}}
as default. And it rejects more tasks if the queue is full.
> When {{BlockManager#maxReplicationStream}} is larger than {{ErasureCodingWorker#stripedReconstructionPool#corePoolSize/maxPoolSize}},
for example, {{maxReplicationStream=20}} and {{corePoolSize=2 , maxPoolSize=8}}.  Meanwhile,
NN sends up to {{maxTransfer}} reconstruction tasks to DN for each heartbeat, and it is calculated
in {{FSNamesystem}}:
> {code}
> final int maxTransfer = blockManager.getMaxReplicationStreams() - xmitsInProgress;
> {code}
> However, at any giving time, {{{ErasureCodingWorker#stripedReconstructionPool}} takes
2 {{xmitInProcess}}. So for each heartbeat in 3s, NN will send about {{20-2 = 18}} reconstruction
tasks to the DN, and DN throw away most of them if there were 8 tasks in the queue already.
So NN needs to take longer to re-consider these blocks were under-replicated to schedule new
tasks.



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