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From "Hudson (Commented) (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (MAPREDUCE-3721) Race in shuffle can cause it to hang
Date Thu, 26 Jan 2012 05:47:43 GMT

    [ https://issues.apache.org/jira/browse/MAPREDUCE-3721?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13193567#comment-13193567
] 

Hudson commented on MAPREDUCE-3721:
-----------------------------------

Integrated in Hadoop-Hdfs-trunk-Commit #1660 (See [https://builds.apache.org/job/Hadoop-Hdfs-trunk-Commit/1660/])
    MAPREDUCE-3721. Fixed a race in shuffle which caused reduces to hang. Contributed by Siddharth
Seth.

acmurthy : http://svn.apache.org/viewcvs.cgi/?root=Apache-SVN&view=rev&rev=1236041
Files : 
* /hadoop/common/trunk/hadoop-mapreduce-project/CHANGES.txt
* /hadoop/common/trunk/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-core/src/main/java/org/apache/hadoop/mapreduce/task/reduce/MergeManager.java

                
> Race in shuffle can cause it to hang
> ------------------------------------
>
>                 Key: MAPREDUCE-3721
>                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-3721
>             Project: Hadoop Map/Reduce
>          Issue Type: Bug
>          Components: mrv2
>    Affects Versions: 0.23.0
>            Reporter: Siddharth Seth
>            Assignee: Siddharth Seth
>            Priority: Blocker
>             Fix For: 0.23.1
>
>         Attachments: MR-3721.txt
>
>
> If all current {{Fetcher}}s complete while an in-memory merge is in progress - shuffle
could hang. 
> Specifically - if the memory freed by an in-memory merge does not bring {{MergeManager.usedMemory}}
below {{MergeManager.memoryLimit}} and all current Fetchers complete before the in-memory
merge completes, another in-memory merge will not be triggered - and shuffle will hang. (All
new fetchers are asked to WAIT).

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