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Posted to mapreduce-issues@hadoop.apache.org by "Karthik Kambatla (JIRA)" <ji...@apache.org> on 2014/07/03 07:33:49 UTC
[jira] [Updated] (MAPREDUCE-5932) Provide an option to use a
dedicated reduce-side shuffle log
[ https://issues.apache.org/jira/browse/MAPREDUCE-5932?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Karthik Kambatla updated MAPREDUCE-5932:
----------------------------------------
Target Version/s: 2.6.0 (was: 2.5.0)
> 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
>
>
> 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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