[
https://issues.apache.org/jira/browse/YARN-1769?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13919506#comment-13919506
]
Thomas Graves commented on YARN-1769:
-------------------------------------
if canAllocContainer is false then you can't reserve another container. This
could happen if you don't have any containers to unreserve when you hit the
reservation limits and this node doesn't have available containers.
if ((!scheduler.getConfiguration().getReservationContinueLook()) //
without feature always reserve like previously did
|| (canAllocContainer) // if we hit our reservation limit and no
available space on this node, don't reserve another one
|| (rmContainer != null)) { // if this was called because node
already had reservation, we need to make sure it gets book keeped as
re-reservation
I can simplify this a bit. I don't really need the
!scheduler.getConfiguration().getReservationContinueLook check anymore since
canAllocContainer defaults to true in that case.
> CapacityScheduler: Improve reservations
> ----------------------------------------
>
> Key: YARN-1769
> URL: https://issues.apache.org/jira/browse/YARN-1769
> Project: Hadoop YARN
> Issue Type: Improvement
> Components: capacityscheduler
> Affects Versions: 2.3.0
> Reporter: Thomas Graves
> Assignee: Thomas Graves
> Attachments: YARN-1769.patch
>
>
> Currently the CapacityScheduler uses reservations in order to handle requests
> for large containers and the fact there might not currently be enough space
> available on a single host.
> The current algorithm for reservations is to reserve as many containers as
> currently required and then it will start to reserve more above that after a
> certain number of re-reservations (currently biased against larger
> containers). Anytime it hits the limit of number reserved it stops looking
> at any other nodes. This results in potentially missing nodes that have
> enough space to fullfill the request.
> The other place for improvement is currently reservations count against your
> queue capacity. If you have reservations you could hit the various limits
> which would then stop you from looking further at that node.
> The above 2 cases can cause an application requesting a larger container to
> take a long time to gets it resources.
> We could improve upon both of those by simply continuing to look at incoming
> nodes to see if we could potentially swap out a reservation for an actual
> allocation.
--
This message was sent by Atlassian JIRA
(v6.2#6252)
