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https://issues.apache.org/jira/browse/YARN-3405?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14384363#comment-14384363
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zhihai xu commented on YARN-3405:
---------------------------------
[~kasha] is right, There is a possibility for the first scenario. If we have
another queue queue-2 which is queue-1's sibling and queue-2 is greater than
queue-1 when compare queue-1 and queue-2, then queue-2 will always be picked
for preemption and queue-1 won't have chance to be preempted.
> 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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