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From "Peng Zhang (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (YARN-3405) FairScheduler's preemption cannot happen between sibling in some case
Date Fri, 27 Mar 2015 10:11:53 GMT

    [ https://issues.apache.org/jira/browse/YARN-3405?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14383615#comment-14383615
] 

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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