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https://issues.apache.org/jira/browse/MAPREDUCE-5268?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13671582#comment-13671582
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Jason Lowe commented on MAPREDUCE-5268:
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Wow, that was fast! Unfortunately ConcurrentSkipListMapWithSize is still
showing up in filenames.
Also taking a closer look at the unit tests, FakeJobId should be removed and
replaced with MRBuilderUtils.newJobId. There's a form of that method where we
can simply pass numbers for the cluster timestamp, app ID, and job ID directly.
> Improve history server startup performance
> ------------------------------------------
>
> Key: MAPREDUCE-5268
> URL: https://issues.apache.org/jira/browse/MAPREDUCE-5268
> Project: Hadoop Map/Reduce
> Issue Type: Improvement
> Components: jobhistoryserver
> Affects Versions: 0.23.7, 2.0.4-alpha
> Reporter: Jason Lowe
> Assignee: Karthik Kambatla
> Attachments: mr-5268.patch, mr-5268.patch, mr-5268.patch,
> mr-5268.patch, mr-5268-prelim.patch
>
>
> The history server can easily take many minutes to startup when there are a
> significant number of jobs to scan in the done directory. However the
> scanning of files is not the bottleneck, rather it's the heavy use of
> ConcurrentSkipListMap.size in HistoryFileManager.
> ConcurrentSkipListMap.size is a very expensive operation, especially on maps
> with many entries, as it has to scan every entry to compute the size. We
> should avoid calling this method or at least minimize its use.
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