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https://issues.apache.org/jira/browse/YARN-3405?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14383469#comment-14383469
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Peng Zhang commented on YARN-3405:
----------------------------------
And there is another related case which will cause live lock during preemption
and scheduling.
If necessary, I will create a separated issue for it.
Queue hierarchy described as below:
{noformat}
root
/ | \
queue-1 queue-2 queue-3
/ \
queue-1-1 queue-1-2
{noformat}
# Assume cluster resource is 100G in memory
# Assume queue-1 has max resource limit 20G
# queue-1-1 is active and it will get max 20G memory(equal to its fairshare)
# queue-2 is active then, and it require 30G memory(less than its fairshare)
# queue-3 is active, and it can be assigned with all other resources, 50G
memory(larger than its fairshare)
# queue-1-2 is active, it will cause new preemption request(10G memory and
intuitively it can only preempt from its sibling queue-1-1)
# Actually preemption starts from root, and it will find queue-3 is most over
fairshare, and preempt some resources form queue-3.
# But during scheduling, it will find queue-1 itself arrived it's max
fairshare, and cannot assign resource to it. Then resource's again assigned to
queue-3
And then it repeats between last two steps.
> 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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