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https://issues.apache.org/jira/browse/MAPREDUCE-5308?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13680401#comment-13680401
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Hudson commented on MAPREDUCE-5308:
-----------------------------------
Integrated in Hadoop-Mapreduce-trunk #1454 (See
[https://builds.apache.org/job/Hadoop-Mapreduce-trunk/1454/])
MAPREDUCE-5308. Shuffling to memory can get out-of-sync when fetching
multiple compressed map outputs. Contributed by Nathan Roberts (Revision
1491611)
Result = SUCCESS
jlowe : http://svn.apache.org/viewcvs.cgi/?root=Apache-SVN&view=rev&rev=1491611
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/InMemoryMapOutput.java
*
/hadoop/common/trunk/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-core/src/test/java/org/apache/hadoop/mapreduce/task/reduce/TestFetcher.java
> Shuffling to memory can get out-of-sync when fetching multiple compressed map
> outputs
> -------------------------------------------------------------------------------------
>
> Key: MAPREDUCE-5308
> URL: https://issues.apache.org/jira/browse/MAPREDUCE-5308
> Project: Hadoop Map/Reduce
> Issue Type: Bug
> Affects Versions: trunk, 2.0.3-alpha, 0.23.8
> Reporter: Nathan Roberts
> Assignee: Nathan Roberts
> Fix For: 2.1.0-beta, 0.23.9
>
> Attachments: MAPREDUCE-5308-branch-0.23.txt, MAPREDUCE-5308.patch
>
>
> When a reducer is fetching multiple compressed map outputs from a host, the
> fetcher can get out-of-sync with the IFileInputStream, causing several of the
> maps to fail to fetch.
> This occurs because decompressors can return all the decompressed bytes
> before actually processing all the bytes in the compressed stream (due to
> checksums or other trailing data that we ignore). In the unfortunate case
> where these extra bytes cross an io.file.buffer.size boundary, some extra
> bytes will be left over and the next map_output will not fetch correctly
> (usually due to an invalid map_id).
> This scenario is not typically fatal to a job because the failure is charged
> to the map_output immediately following the "bad" one and the subsequent
> retry will normally work.
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