[jira] [Commented] (YARN-4287) Capacity Scheduler: Rack Locality improvement

["Wangda Tan (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/YARN-4287?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14997573#comment-14997573 ] 

Wangda Tan commented on YARN-4287:
----------------------------------

Thanks for update, [~nroberts].

Patch generally looks good, few comments:
- Could you add a comment at
{code}
      return (Math.min(rmContext.getScheduler().getNumClusterNodes(), 
          (requiredContainers * localityWaitFactor)) < missedOpportunities);
{code}
People read the code can get better understanding that why missedOpportunity need to be capped by numClusterNodes
- I would suggest to add tests for missedOpportunity capped by numClusterNodes and resetSchedulingOpportunity for rack request.

> Capacity Scheduler: Rack Locality improvement
> ---------------------------------------------
>
>                 Key: YARN-4287
>                 URL: https://issues.apache.org/jira/browse/YARN-4287
>             Project: Hadoop YARN
>          Issue Type: Improvement
>          Components: capacityscheduler
>    Affects Versions: 2.7.1
>            Reporter: Nathan Roberts
>            Assignee: Nathan Roberts
>         Attachments: YARN-4287-minimal-v2.patch, YARN-4287-minimal-v3.patch, YARN-4287-minimal.patch, YARN-4287-v2.patch, YARN-4287-v3.patch, YARN-4287-v4.patch, YARN-4287.patch
>
>
> YARN-4189 does an excellent job describing the issues with the current delay scheduling algorithms within the capacity scheduler. The design proposal also seems like a good direction.
> This jira proposes a simple interim solution to the key issue we've been experiencing on a regular basis:
>  - rackLocal assignments trickle out due to nodeLocalityDelay. This can have significant impact on things like CombineFileInputFormat which targets very specific nodes in its split calculations.
> I'm not sure when YARN-4189 will become reality so I thought a simple interim patch might make sense. The basic idea is simple: 
> 1) Separate delays for rackLocal, and OffSwitch (today there is only 1)
> 2) When we're getting rackLocal assignments, subsequent rackLocal assignments should not be delayed
> Patch will be uploaded shortly. No big deal if the consensus is to go straight to YARN-4189. 



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