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https://issues.apache.org/jira/browse/MAPREDUCE-5932?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14218566#comment-14218566
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Jason Lowe commented on MAPREDUCE-5932:
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Thanks for updating the patch, Gera. Could you look into the test failures?
They seem related. Other comments on the patch:
There's already a conf to tell if the task is a map or a reduce, see
MRJobConfig.TASK_ISMAP. We shouldn't need MRJobConfig.REDUCE_CONTAINER.
The new properties should be added to mapred-default.xml for documentation
purposes.
> Provide an option to use a dedicated reduce-side shuffle log
> ------------------------------------------------------------
>
> Key: MAPREDUCE-5932
> URL: https://issues.apache.org/jira/browse/MAPREDUCE-5932
> Project: Hadoop Map/Reduce
> Issue Type: Improvement
> Components: mrv2
> Affects Versions: 2.4.0
> Reporter: Gera Shegalov
> Assignee: Gera Shegalov
> Attachments: MAPREDUCE-5932.v01.patch, MAPREDUCE-5932.v02.patch,
> MAPREDUCE-5932.v03.patch
>
>
> For reducers in large jobs our users cannot easily spot portions of the log
> associated with problems with their code. An example reducer with INFO-level
> logging generates ~3500 lines / ~700KiB lines per second. 95% of the log is
> the client-side of the shuffle {{org.apache.hadoop.mapreduce.task.reduce.*}}
> {code}
> $ wc syslog
> 3642 48192 691013 syslog
> $ grep task.reduce syslog | wc
> 3424 46534 659038
> $ grep task.reduce.ShuffleScheduler syslog | wc
> 1521 17745 251458
> $ grep task.reduce.Fetcher syslog | wc
> 1045 15340 223683
> $ grep task.reduce.InMemoryMapOutput syslog | wc
> 400 4800 72060
> $ grep task.reduce.MergeManagerImpl syslog | wc
> 432 8200 106555
> {code}
> Byte percentage breakdown:
> {code}
> Shuffle total: 95%
> ShuffleScheduler: 36%
> Fetcher: 32%
> InMemoryMapOutput: 10%
> MergeManagerImpl: 15%
> {code}
> While this is information is actually often useful for devops debugging
> shuffle performance issues, the job users are often lost.
> We propose to have a dedicated syslog.shuffle file.
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