[jira] [Commented] (YARN-2009) Priority support for preemption in ProportionalCapacityPreemptionPolicy

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

    [ https://issues.apache.org/jira/browse/YARN-2009?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15543523#comment-15543523 ] 

Eric Payne commented on YARN-2009:
----------------------------------

Hi [~sunilg],

I noticed some odd behavior while trying the following use case:
# {{User1}} starts {{app1}} at {{priority1}} and consumes the entire queue
# {{User1}} starts {{app2}} at {{priority2}}
# preemption happens for all containers from {{app1}} except the AM container
# {{app2}} consumes all containers released by {{app1}}
# The preemption monitor preempts containers from {{_app2_}}! This continues as long as {{app2}} runs.

I believe it is caused by the following code:
{code:title=FifoIntraQueuePreemptionPolicy#getResourceDemandFromAppsPerQueue}
    Collection<TempAppPerPartition> appsOrderedByPriority = tq.getApps();
    Resource actualPreemptNeeded = null;

    for (TempAppPerPartition a1 : appsOrderedByPriority) {
      for (String label : a1.getPartitions()) {

        // Updating pending resource per-partition level.
        if ((actualPreemptNeeded = resToObtainByPartition.get(label)) == null) {
          actualPreemptNeeded = Resources.createResource(0, 0);
          resToObtainByPartition.put(label, actualPreemptNeeded);
        }
        Resources.addTo(actualPreemptNeeded, a1.getActuallyToBePreempted());
      }
    }
    return resToObtainByPartition;
{code}

Since {{app1}}'s AM container is still running, the size of {{actuallyToBePreempted}} for {{app1}} is the size of the AM's container. This gets added to {{actualPreemptNeeded}} and put into {{actualPreemptNeeded}}, which then gets passed to {{IntraQueueCandidatesSelector#preemptFromLeastStarvedApp}}. {{preemptFromLeastStarvedApp}} skips {{app1}}'s AM, and then preempts from the only remaining thing with resources, which is {{app2}}.

I'm not sure exactly how I would fix this yet, except to consider the size of the AM when calculating {{actuallyToBePreempted}}.

> Priority support for preemption in ProportionalCapacityPreemptionPolicy
> -----------------------------------------------------------------------
>
>                 Key: YARN-2009
>                 URL: https://issues.apache.org/jira/browse/YARN-2009
>             Project: Hadoop YARN
>          Issue Type: Sub-task
>          Components: capacityscheduler
>            Reporter: Devaraj K
>            Assignee: Sunil G
>         Attachments: YARN-2009.0001.patch, YARN-2009.0002.patch, YARN-2009.0003.patch, YARN-2009.0004.patch
>
>
> While preempting containers based on the queue ideal assignment, we may need to consider preempting the low priority application containers first.



--
This message was sent by Atlassian JIRA
(v6.3.4#6332)

---------------------------------------------------------------------
To unsubscribe, e-mail: yarn-issues-unsubscribe@hadoop.apache.org
For additional commands, e-mail: yarn-issues-help@hadoop.apache.org