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https://issues.apache.org/jira/browse/YARN-4963?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15245187#comment-15245187
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Rohith Sharma K S commented on YARN-4963:
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Thanks [~nroberts] for initiating discussion on this. We have seen off_switch
assignment issue in large cluster as you described. Especially when cluster is
running fully occupied resource, and container release happens all together
from one node, only 1 container is assigned this node. This makes user thinks
that why assignment is not happening even though resource is free.
IMO, I think application specific configurations should be there rather at
scheduler level. Some applications are fine with assigning containers in
off_switch they can specify number of containers to be assigned. But few
applications are very strict to node locality, they can configure 1 in
off_switch.
Thoughts?
> capacity scheduler: Make number of OFF_SWITCH assignments per heartbeat
> configurable
> ------------------------------------------------------------------------------------
>
> Key: YARN-4963
> URL: https://issues.apache.org/jira/browse/YARN-4963
> Project: Hadoop YARN
> Issue Type: Improvement
> Components: capacityscheduler
> Affects Versions: 3.0.0, 2.7.2
> Reporter: Nathan Roberts
> Assignee: Nathan Roberts
> Attachments: YARN-4963.001.patch
>
>
> Currently the capacity scheduler will allow exactly 1 OFF_SWITCH assignment
> per heartbeat. With more and more non MapReduce workloads coming along, the
> degree of locality is declining, causing scheduling to be significantly
> slower. It's still important to limit the number of OFF_SWITCH assignments to
> avoid densely packing OFF_SWITCH containers onto nodes.
> Proposal is to add a simple config that makes the number of OFF_SWITCH
> assignments configurable.
> Will upload candidate patch shortly.
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