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https://issues.apache.org/jira/browse/YARN-7839?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16343069#comment-16343069
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Weiwei Yang commented on YARN-7839:
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Hi [~asuresh]
When there is multiple threads running placement algorithm, it could be true
when you check a node capacity in both places, but eventually got rejected when
some other container allocated to this node. As you don't hold the
SchedulerNode's lock to update resource when you attempt to place the request.
So I am not sure how much this can improve in a highly utilized cluster.
Instead, I am thinking... can we generate *a list of ordered candidate nodes*
for each allocation (based on some policy), then let scheduler work on such
candidate set of nodes to pick up one that fulfills scheduler's requests?
Thanks
> Check node capacity before placing in the Algorithm
> ---------------------------------------------------
>
> Key: YARN-7839
> URL: https://issues.apache.org/jira/browse/YARN-7839
> Project: Hadoop YARN
> Issue Type: Sub-task
> Reporter: Arun Suresh
> Priority: Major
>
> Currently, the Algorithm assigns a node to a requests purely based on if the
> constraints are met. It is later in the scheduling phase that the Queue
> capacity and Node capacity are checked. If the request cannot be placed
> because of unavailable Queue/Node capacity, the request is retried by the
> Algorithm.
> For clusters that are running at high utilization, we can reduce the retries
> if we perform the Node capacity check in the Algorithm as well. The Queue
> capacity check and the other user limit checks can still be handled by the
> scheduler (since queues and other limits are tied to the scheduler, and not
> scheduler agnostic)
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