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https://issues.apache.org/jira/browse/YARN-3405?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14383615#comment-14383615
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Peng Zhang commented on YARN-3405:
----------------------------------
[~zxu]
I have verified that there's no problem in first scenario.
Second scenario problem still exists.
bq. And If queue1 level has some other sibling queue(like queue-2) that equals
to queue-1's usage/fairshare, "candidateQueue" still may be not the queue-1
itself, because they are equal by comparing, and will depends on the queue
order.Then queue-1-2 still cannot preempt its sibling, and cause some live lock
issue like above second scenario.
I think for above scenario it maybe results in preemptContainerPreCheck() for
queue-2 (leaf queue) will fail, and queue-1-2 cannot get preempt any resources.
Live lock will not happen.
I'll update description once you committed above bad cases.
Thanks.
> FairScheduler's preemption cannot happen between sibling in some case
> ---------------------------------------------------------------------
>
> Key: YARN-3405
> URL: https://issues.apache.org/jira/browse/YARN-3405
> Project: Hadoop YARN
> Issue Type: Bug
> Components: fairscheduler
> Affects Versions: 2.7.0
> Reporter: Peng Zhang
> Priority: Critical
>
> Queue hierarchy described as below:
> {noformat}
> root
> |
> queue-1
> / \
> queue-1-1 queue-1-2
> {noformat}
> 1. When queue-1-1 is active and it has been assigned with all resources.
> 2. When queue-1-2 is active, and it cause some new preemption request.
> 3. But when do preemption, it now starts from root, and found queue-1 is not
> over fairshare, so no recursion preemption to queue-1-1.
> 4. Finally queue-1-2 will be waiting for resource release form queue-1-1
> itself.
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