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From "Wangda Tan (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (YARN-5864) Capacity Scheduler preemption for fragmented cluster
Date Thu, 17 Nov 2016 18:41:58 GMT

    [ https://issues.apache.org/jira/browse/YARN-5864?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15674481#comment-15674481
] 

Wangda Tan commented on YARN-5864:
----------------------------------

Thanks [~curino] for sharing the firmament paper. I just read it, it provided a lot of insightful
ideas. I believe it can work pretty well for a cluster which have homogeneous workload, but
it may not be able to solve the mix workloads issues, as it stated:

bq. Firmament shows that a single scheduler can attain scalability, but its MCMF optimization
does not trivially admit multiple independent schedulers. 

So in my mind, for YARN, we need borg-like architecture to make different kinds of workload
can be scheduled using different pluggable scheduling policies and scorers. Firmament could
be one of these scheduling policies. 

I agree your comment about we should make a better semantics of the feature, I will think
it again and keep you posted.

> Capacity Scheduler preemption for fragmented cluster 
> -----------------------------------------------------
>
>                 Key: YARN-5864
>                 URL: https://issues.apache.org/jira/browse/YARN-5864
>             Project: Hadoop YARN
>          Issue Type: New Feature
>            Reporter: Wangda Tan
>            Assignee: Wangda Tan
>         Attachments: YARN-5864.poc-0.patch
>
>
> YARN-4390 added preemption for reserved container. However, we found one case that large
container cannot be allocated even if all queues are under their limit.
> For example, we have:
> {code}
> Two queues, a and b, capacity 50:50 
> Two nodes: n1 and n2, each of them have 50 resource 
> Now queue-a uses 10 on n1 and 10 on n2
> queue-b asks for one single container with resource=45. 
> {code} 
> The container could be reserved on any of the host, but no preemption will happen because
all queues are under their limits. 



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