[jira] [Commented] (YARN-4781) Support intra-queue preemption for fairness ordering policy.

["Eric Payne (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/YARN-4781?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16424281#comment-16424281 ] 

Eric Payne commented on YARN-4781:
----------------------------------

Thanks very much [~sunilg] for the review.
{quote}FairOrderingPolicy comparator also considers pending resource of an application.
{quote}
I'm not seeing the {{FairOrderingPolicy}} consider pending + used. Here's what I'm looking at. Maybe you can show me what I'm missing:
{code:java|title=FairOrderingPolicy#FairComparator}
    public int compare(final SchedulableEntity r1, final SchedulableEntity r2) {
      int res = (int) Math.signum( getMagnitude(r1) - getMagnitude(r2) );
      return res;
    }
{code}
{quote}Cud u pls check the findbugs warnings
{quote}
I cut and pasted the {{TAPriorityComparator}} to create the {{TAFairOrderingComparator}}. Findbugs is complaining about the {{TAFairOrderingComparator}} being {{Serializable}} but having non-serializable fields. I don't think these comparators need to be {{Serializable}}, do they? None of the other comparators (that I could see) in the capacity scheduler implement {{Serializable}}. I took out the {{implements}} for that.
{quote}Similar to testIntraQueuePreemptionFairOrderingPolicyMulitipleAppsPerUser, cud we also have a test where we have multiple apps are there per user. So among user's we ll select young app for preemption.
{quote}
Added a test case. Thanks.

> Support intra-queue preemption for fairness ordering policy.
> ------------------------------------------------------------
>
>                 Key: YARN-4781
>                 URL: https://issues.apache.org/jira/browse/YARN-4781
>             Project: Hadoop YARN
>          Issue Type: Sub-task
>          Components: scheduler
>            Reporter: Wangda Tan
>            Assignee: Wangda Tan
>            Priority: Major
>         Attachments: YARN-4781.001.patch, YARN-4781.002.patch, YARN-4781.003.patch
>
>
> We introduced fairness queue policy since YARN-3319, which will let large applications make progresses and not starve small applications. However, if a large application takes the queue’s resources, and containers of the large app has long lifespan, small applications could still wait for resources for long time and SLAs cannot be guaranteed.
> Instead of wait for application release resources on their own, we need to preempt resources of queue with fairness policy enabled.



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