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https://issues.apache.org/jira/browse/YARN-3510?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14571423#comment-14571423
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Sunil G commented on YARN-3510:
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Hi [~leftnoteasy] and [~cwelch]
Thank you for reply.
As Craig mentioned, I didnt mean the application priority here. I agree to your
point that this is not a new issue as per this patch. The new change will a
make more fair approach in selecting containers across applications, and not
specifically from last submitted application.
The scenario which I mentioned above was a case happened in our test bed. Now
with new patch, App2 will have to relaunch map because it got preempted. In
above example, assume we need to preempt 4 containers. Earlier App1 will kill 4
of its reducers and App2 was not loosing any container. Now we will loose a map
from App2. This is a corner scenario, and in general if the new approach gives
a more fair preemption, then we can move to that. :)
> 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: Sunil G
> 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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