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https://issues.apache.org/jira/browse/MAPREDUCE-7017?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16278207#comment-16278207
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jiayuhan-it commented on MAPREDUCE-7017:
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This invocation would takes 30 minutes with 3000 tasks one time the DNS
configuration is not reasonable.After this optimization it tasks only 2 or 3
minutes.
> Too many times of meaningless invocation in TaskAttemptImpl#resolveHosts
> ------------------------------------------------------------------------
>
> Key: MAPREDUCE-7017
> URL: https://issues.apache.org/jira/browse/MAPREDUCE-7017
> Project: Hadoop Map/Reduce
> Issue Type: Improvement
> Components: mr-am
> Affects Versions: 3.0.0-alpha4
> Reporter: jiayuhan-it
> Attachments: MAPREDUCE-7017.001.patch
>
>
> MRAppMaster uses {{TaskAttemptImpl::resolveHosts}} to determine the
> dataLocalHosts for each task when the location of data split is IP, which
> will call a lot of times ( taskNum * dfsReplication) of function
> {{InetAddress::getByName}} and most of the funcition calls are redundant.
> When the job has a great number of tasks and the speed of DNS resolution is
> not fast enough, it will take a lot of time at this stage before the job
> running.
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