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https://issues.apache.org/jira/browse/MAPREDUCE-3512?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13183737#comment-13183737
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Siddharth Seth commented on MAPREDUCE-3512:
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Had run some crude benchmarks - writing out about 40MB of data (iirc). With a
flush after every 0.5KB - this took roughly 35 seconds. With one flush at the
end - around 6 seconds. Flush every 500KB - about 12 seconds.
Also, a benchmark like AMScalability (100K map tasks) currently takes over 5
minutes after job complete to finish the history file.
> Batch jobHistory disk flushes
> -----------------------------
>
> Key: MAPREDUCE-3512
> URL: https://issues.apache.org/jira/browse/MAPREDUCE-3512
> Project: Hadoop Map/Reduce
> Issue Type: Sub-task
> Components: mr-am, mrv2
> Affects Versions: 0.23.0
> Reporter: Siddharth Seth
> Assignee: Siddharth Seth
> Priority: Blocker
> Attachments: MR3512.txt, MR3512.txt
>
>
> The mr-am flushes each individual job history event to disk for AM recovery.
> The history even handler ends up with a significant backlog for tests like
> MAPREDUCE-3402.
> History events could be batched up based on num records / time /
> TaskFinishedEvents to reduce the number of DFS writes - with the potential
> drawback of having to rerun some tasks during AM recovery.
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