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https://issues.apache.org/jira/browse/YARN-5829?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15904584#comment-15904584
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Tao Jie commented on YARN-5829:
-------------------------------
Thank you [~miklos.szeg...@cloudera.com] for sharing your thought.
1, It is easy to confuse the reservation we are taking about with the current
reservation mechanism in scheduler. IIRC, the purpose of current reservation is
to prevent starvation of request with large resource. And our reservation here
is to assign container on node to one exact application.
2, I feel both OK about 1)reuse/extend current reservation mechanism or 2)add
another logic to handle the reservation for preemption. If is 2), it's better
to find another name to avoid naming confusion.
3,
{quote}
2. We also need to be careful with prioritizing reservations. For example how
it works now is that a reservation takes priority before any other request.
What happens, if I have a preemption from a lower priority request but there is
a demand from a higher priority application?
{quote}
In my opinion, the reservation for preemption should have higher priority than
current reservation in allocation. If starved application that triggers
preempting is not satisfied as soon as possible, it will still in starvation
and try to preempt more containers. However a normal application has
reservation container on nodes would wait for a while since the resource is
allocated to another starved application, it makes sense that application would
get higher priority when itself becomes a starved application.
> FS preemption should reserve a node before considering containers on it for
> preemption
> --------------------------------------------------------------------------------------
>
> Key: YARN-5829
> URL: https://issues.apache.org/jira/browse/YARN-5829
> Project: Hadoop YARN
> Issue Type: Sub-task
> Components: fairscheduler
> Reporter: Karthik Kambatla
> Assignee: Miklos Szegedi
>
> FS preemption evaluates nodes for preemption, and subsequently preempts
> identified containers. If this node is not reserved for a specific
> application, any other application could be allocated resources on this node.
> Reserving the node for the starved application before preempting containers
> would help avoid this.
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