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https://issues.apache.org/jira/browse/MAPREDUCE-7017?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16281660#comment-16281660
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jiayuhan-it edited comment on MAPREDUCE-7017 at 12/7/17 10:42 AM:
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cc [~asuresh] and @Konstantinos Karanasos
Please help to review. 


was (Author: magicbunny):
cc @Arun Suresh and @Konstantinos Karanasos
Please help to review. 

> 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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