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https://issues.apache.org/jira/browse/YARN-392?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13583792#comment-13583792
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Sandy Ryza commented on YARN-392:
---------------------------------
The proposal of per-app delay-scheduling parameters is one I hadn't thought of,
and I think a good one for many use cases. Do you mean that the delay
threshold would be configurable per-app or per-priority?
The cases that I don't think it supports are:
* If the delay threshold is only configurable per app, an app needs some
containers strictly on specific nodes, and for other containers only has loose
preferences.
* An application wants two containers, the first on only node1 or node2 and the
second on only node3 or node4. What tells the scheduler not to assign both of
the containers on node1 and node2? These containers could be requested at
different priorities, but that would essentially be using priorities to do
task-centric scheduling.
Are these use cases non-goals for YARN? Correct me if I'm wrong, but my
understanding was that the primary reason that the resource scheduler is not a
task scheduler is for performance reasons. If we can allow it to be
task-centric when necessary, but avoid the performance impact of making it
task-centric all the time, it will support location-specific scheduling in the
most flexible and intuitive way.
I hope this isn't rehashing the debate from YARN-371. For anybody who will be
the YARN meetup tomorrow, it would be great to chat about this for a couple
minutes.
> Make it possible to schedule to specific nodes without dropping locality
> ------------------------------------------------------------------------
>
> Key: YARN-392
> URL: https://issues.apache.org/jira/browse/YARN-392
> Project: Hadoop YARN
> Issue Type: Sub-task
> Reporter: Bikas Saha
> Assignee: Sandy Ryza
> Attachments: YARN-392.patch
>
>
> Currently its not possible to specify scheduling requests for specific nodes
> and nowhere else. The RM automatically relaxes locality to rack and * and
> assigns non-specified machines to the app.
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