[jira] [Commented] (YARN-3054) Preempt policy in FairScheduler may cause mapreduce job never finish

["Karthik Kambatla (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/YARN-3054?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15186463#comment-15186463 ] 

Karthik Kambatla commented on YARN-3054:
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[~peng.zhang] - the problem reported is not quite clear, mind elaborating it further? 

> Preempt policy in FairScheduler may cause mapreduce job never finish
> --------------------------------------------------------------------
>
>                 Key: YARN-3054
>                 URL: https://issues.apache.org/jira/browse/YARN-3054
>             Project: Hadoop YARN
>          Issue Type: Sub-task
>          Components: fairscheduler
>    Affects Versions: 2.6.0
>            Reporter: Peng Zhang
>
> Preemption policy is related with schedule policy now. Using comparator of schedule policy to find preemption candidate cannot guarantee a subset of containers never be preempted. And this may cause tasks to be preempted periodically before they finish. So job cannot make any progress. 
> I think preemption in YARN should got below assurance:
> 1. Mapreduce jobs can get additional resources when others are idle;
> 2. Mapreduce jobs for one user in one queue can still progress with its min share when others preempt resources back.
> Maybe always preempt the latest app and container can get this? 



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