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https://issues.apache.org/jira/browse/MAPREDUCE-4815?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14335282#comment-14335282
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Siqi Li commented on MAPREDUCE-4815:
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Thanks for your feedback [~jira.shegalov]. I have updated patch v15, which
resolves 80 characters violations in mapred.TestFileOutputCommitter.
Also, I have added some more documentation in mapred-default.xml, including
behavior of algorithm 1, and not to do rolling upgrade.
As for output.FileOutputCommitter, I have replace fs.exist(taskAttemptPath)
with fs.getFileStatus(taskAttemptPath).
> FileOutputCommitter.commitJob can be very slow for jobs with many output files
> ------------------------------------------------------------------------------
>
> Key: MAPREDUCE-4815
> URL: https://issues.apache.org/jira/browse/MAPREDUCE-4815
> Project: Hadoop Map/Reduce
> Issue Type: Bug
> Components: mrv2
> Affects Versions: 0.23.3, 2.0.1-alpha, 2.4.1
> Reporter: Jason Lowe
> Assignee: Siqi Li
> Attachments: MAPREDUCE-4815.v10.patch, MAPREDUCE-4815.v11.patch,
> MAPREDUCE-4815.v12.patch, MAPREDUCE-4815.v13.patch, MAPREDUCE-4815.v14.patch,
> MAPREDUCE-4815.v15.patch, MAPREDUCE-4815.v3.patch, MAPREDUCE-4815.v4.patch,
> MAPREDUCE-4815.v5.patch, MAPREDUCE-4815.v6.patch, MAPREDUCE-4815.v7.patch,
> MAPREDUCE-4815.v8.patch, MAPREDUCE-4815.v9.patch
>
>
> If a job generates many files to commit then the commitJob method call at the
> end of the job can take minutes. This is a performance regression from 1.x,
> as 1.x had the tasks commit directly to the final output directory as they
> were completing and commitJob had very little to do. The commit work was
> processed in parallel and overlapped the processing of outstanding tasks. In
> 0.23/2.x, the commit is single-threaded and waits until all tasks have
> completed before commencing.
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