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https://issues.apache.org/jira/browse/MAPREDUCE-7158?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16684546#comment-16684546
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Zichen Sun commented on MAPREDUCE-7158:
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the patch has no functionality change, it's been verified in a test cluster
using 10TB benchmark data and we the performance is much improved
> Inefficient Flush Logic in JobHistory EventWriter
> -------------------------------------------------
>
> Key: MAPREDUCE-7158
> URL: https://issues.apache.org/jira/browse/MAPREDUCE-7158
> Project: Hadoop Map/Reduce
> Issue Type: Bug
> Affects Versions: 3.2.0
> Reporter: Zichen Sun
> Priority: Major
> Attachments: MAPREDUCE-7158-001.patch
>
>
> In HDFS, if the flush is implemented to send server request to actually
> commit the pending writes on the storage service side, we could observe in
> the benchmark runs that the MR jobs are taking much longer. From
> investigation we see the current implementation for writing events doesn't
> look right:
> EventWriter# write()
> This flush is redundant and this statement should be removed. It defeats the
> purpose of having a separate flush function itself.
> Encoder.flush calls flush of the underlying output stream
> After patching with the fix the MR jobs could complete normally, please
> kindly find the patch in attached.
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