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https://issues.apache.org/jira/browse/YARN-2113?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15971707#comment-15971707
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Eric Payne commented on YARN-2113:
----------------------------------
[~leftnoteasy], it looks good in general, but I did discover a corner case that
causes unnecessary preemption that will kill a container, give it back to the
one killed, and kill it again ("flapping").
The following code returns true if {{user.used > user.userLimit}}:
{code:title=TempUserPerPartition#isUserLimitReached}
public boolean isUserLimitReached(ResourceCalculator rc,
Resource clusterResource) {
if (Resources.greaterThan(rc, clusterResource, getUsedDeductAM(),
userLimit)) {
return true;
}
return false;
}
{code}
The algorithm for Capacity Scheduler is to assign one container more than the
user limit. So, if
- {{user1 / app1}} is 1 container above their user limit
- {{user2 / app2)) is below its user limit
The above {{isUserLimitReached}} method will return true, 1 container will be
preempted from {{app1}}, {{user1}} will fall down to its user limit, and the
Capacity Scheduler will give the container back to {{app1}}.
I can reproduce this regularly. Do you think this is a sufficient corner case
that we can address it as part of a separate JIRA?
> Add cross-user preemption within CapacityScheduler's leaf-queue
> ---------------------------------------------------------------
>
> Key: YARN-2113
> URL: https://issues.apache.org/jira/browse/YARN-2113
> Project: Hadoop YARN
> Issue Type: Sub-task
> Components: scheduler
> Reporter: Vinod Kumar Vavilapalli
> Assignee: Sunil G
> Attachments:
> TestNoIntraQueuePreemptionIfBelowUserLimitAndDifferentPrioritiesWithExtraUsers.txt,
> YARN-2113.0001.patch, YARN-2113.0002.patch, YARN-2113.0003.patch,
> YARN-2113.0004.patch, YARN-2113.0005.patch, YARN-2113.0006.patch,
> YARN-2113.0007.patch, YARN-2113.v0.patch
>
>
> Preemption today only works across queues and moves around resources across
> queues per demand and usage. We should also have user-level preemption within
> a queue, to balance capacity across users in a predictable manner.
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