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Bikas Saha commented on YARN-45:
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I took a quick look at this patch and the others and from what I see
ResourceRequest is not actionable in the sense that neither of the schedulers
can currently send a non-empty ResourceRequest to preempt. Both only do
preemption by containers though they have some plumbing to send RR's if they
want to do so. So I am not quite sure what you mean by "We indeed have code
that exercises the ResourceRequest version of it". Of course, I may have missed
something.
The following comment may change after a detailed review of the changes in this
patch and other related patches. But as of now I agree with you that RR makes
sense because essentially this request is symmetric. AM uses RR to RM for
resources to schedule and RM uses RR to AM for resources to preempt. By not
using location we are implicitly using the "*" location right? Might as well
make it explicit. Non * locations will make sense when affinity based
preemptions occur.
> Scheduler feedback to AM to release containers
> ----------------------------------------------
>
> Key: YARN-45
> URL: https://issues.apache.org/jira/browse/YARN-45
> Project: Hadoop YARN
> Issue Type: Sub-task
> Components: resourcemanager
> Reporter: Chris Douglas
> Assignee: Carlo Curino
> Attachments: YARN-45.patch, 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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