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https://issues.apache.org/jira/browse/YARN-3510?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14571405#comment-14571405
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Craig Welch commented on YARN-3510:
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[~leftnoteasy], I think [~sunilg] was referring to container priorities, not
application priorities
[~sunilg], container priorities are still taken into account wrt to ordering of
container preemption within an application just as they are today. So
typically an application would not have higher level priority containers
preempted until after any lower level ones had been, and it would only be in
cases where there was a wide discrepancy in usage between applications and a
need for a significant preemption to rebalance queues where I would expect any
given application would end up giving up high priority containers. That's not
actually a new behavior for the capacity scheduler preemption, the existing
logic already works this way.
Put another way, the approach will tend to avoid preempting high priority
containers as a rule, but it could happen as you describe in some cases.
> Create an extension of ProportionalCapacityPreemptionPolicy which preempts a
> number of containers from each application in a way which respects fairness
> --------------------------------------------------------------------------------------------------------------------------------------------------------
>
> Key: YARN-3510
> URL: https://issues.apache.org/jira/browse/YARN-3510
> Project: Hadoop YARN
> Issue Type: Sub-task
> Components: yarn
> Reporter: Craig Welch
> Assignee: Craig Welch
> Attachments: YARN-3510.2.patch, YARN-3510.3.patch, YARN-3510.5.patch,
> YARN-3510.6.patch
>
>
> The ProportionalCapacityPreemptionPolicy preempts as many containers from
> applications as it can during it's preemption run. For fifo this makes
> sense, as it is prempting in reverse order & therefore maintaining the
> primacy of the "oldest". For fair ordering this does not have the desired
> effect - instead, it should preempt a number of containers from each
> application which maintains a fair balance /close to a fair balance between
> them
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