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https://issues.apache.org/jira/browse/YARN-45?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13628358#comment-13628358
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Alejandro Abdelnur commented on YARN-45:
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Carlo, I may be missing something then.
>From your description I'm understanding that a PreemptRequest could contain
>either Set<ContainerID> or Set<ResourceRequest> but not both.
If I'm correct with this assumption, then if the RM chooses to send
Set<ContainerID> then we are back to square one where the RM is deciding what
to kill, it just giving a heads up.
If the idea is that the RM will send PreemptRequest containing both
Set<ContainerID> and Set<ResourceRequest> which are equivalent (just 2 ways of
expressing the same amount of resources), then it seems OK. In this case, the
Set<ContainerID> is just a convenience fo the AM not to go and dig its internal
data structures. But you seem to indicate this is not the case in your second
last paragraph.
I'd argue that the Set<ContainerID> is just an early warning, it does not
delegate the choice to the AM. The fact that the AM could decide to get rid of
another container in the same location and make this preemption to go away
seems twisted.
Regardless of the convenience because of the implementation, I don't think the
RM should cares which containers the AM chooses to release but the amount of
resources.
My specific use case is that that the AM should get an amount of preempt
resources and decide which containers are best to release.
> Scheduler feedback to AM to release containers
> ----------------------------------------------
>
> Key: YARN-45
> URL: https://issues.apache.org/jira/browse/YARN-45
> Project: Hadoop YARN
> Issue Type: Improvement
> Components: resourcemanager
> Reporter: Chris Douglas
> Assignee: Carlo Curino
> Attachments: YARN-45.patch
>
>
> The ResourceManager strikes a balance between cluster utilization and strict
> enforcement of resource invariants in the cluster. Individual allocations of
> containers must be reclaimed- or reserved- to restore the global invariants
> when cluster load shifts. In some cases, the ApplicationMaster can respond to
> fluctuations in resource availability without losing the work already
> completed by that task (MAPREDUCE-4584). Supplying it with this information
> would be helpful for overall cluster utilization [1]. To this end, we want to
> establish a protocol for the RM to ask the AM to release containers.
> [1] http://research.yahoo.com/files/yl-2012-003.pdf
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