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From "Suma Shivaprasad (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (YARN-7117) Capacity Scheduler: Support Auto Creation of Leaf Queues While Doing Queue Mapping
Date Sat, 30 Sep 2017 02:39:02 GMT

    [ https://issues.apache.org/jira/browse/YARN-7117?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16186821#comment-16186821

Suma Shivaprasad commented on YARN-7117:

Thanks for your feedback [~jlowe] the syntax would be more concise and easier to read if the
queue could be specified as a sub-path that can optionally include the parent queue. For example,
rather than u:user1:queue1(parent-queue=marketing) the syntax could be simplified to: u:user1:marketing.queue1.

{quote} Agree .The current CS code has a bug in that it allows "." in the queue names. Do
you think we should fix this for 3.0? {quote}

I'm not really familiar with queue mappings, but I'm assuming the order they are specified
is significant to deterministically resolve cases where more than one specified rule would
apply to a user. If so then the example is confusing since it looks like the u:user2:%primary_group(parent-queue=finance)
rule will always be eclipsed by the preceding u:%user:%user(parent=engineering) rule.

{quote} Good catch. The example needs to be fixed {quote}

IMHO if the admin wants to configure guarantees for auto-created queues then we should not
assume that they're going to be OK with auto-created queues that do not meet those specifications.
Otherwise I'd assume the admin would forgo guaranteed capacities on the auto queues and just
have them carve up the parent queue proportionally.

{quote} Thats a good point. We could have a configuration that allows admins to have parent
queues which allow creation of auto queues with guaranteed resources and fail submissions
when parent doesnt have room. By default this could allow best effort queues as in current
design and could be controlled by admins when they configure the parent queue.

The document implies that there's SLAs with guaranteed capacity auto-queues, but that's clearly
not the case. In the example, it's true that the applications submitted to q4 and q5 eventually
ran with guaranteed capacities. However they waited an unbounded amount of time to start running
which means we cannot always hit SLAs. Users in q1/q2/q3 can collectively deny apps in q4/q5
ever running, for example.

{quote}  This should be addressed by the above configurable policy. SLA guarantees are better
with the admin able to configure parent queues with guaranteed capacities for auto created
leaf queues {quote}

For the alternative approach where all of the queues are "best effort" we don't have to always
have the max-am-resource at 0%. We could specify the max-am as a percent of the max cap for
those queues or a separate config specific to them, or whatever. Or we could have the queues
auto-distribute the capacities of the parent as new queues are added. In other words the auto-queue
capacity is 1/(num auto queues) of the parent and the max-capacity is always 100%. Preemption
can be used to keep the queues fair if one user tries to dominate over the others, but capacities
of underutilized queues can be leveraged by others.

{quote} This could be done though it might be a backward in compatible change. {quote} 

If a user has ACLs to the parent queue then I believe they have those ACLs to the entire hierarchy
of that queue. That means if the parent queue says they can submit then they'll be able to
submit to any auto-queue underneath that parent. We'll either need a new ACL for auto-queue
creation separate from app submission or change the semantics of ACL inheritance for auto-queues.
Probably the former makes more sense and would be more intuitive since admins will be used
to the inheritance features of today's queue ACLs and allow admins to configure parent-queue-privileged
users that can get admin-like access to all the auto-queues of a parent queue but aren't fully
admin users across all queues.

{quote}  Good point. Having separate ACLs  for auto-creation would be better {quote}

I don't know if it's critical to show auto-queues as a different color, but I think it would
be important to be able to determine somehow via the UI that the queue was auto-created so
the admin doesn't wonder why they can't find the queue in the static queue configs. This might
be as simple as a "Auto-Queue: true/false" line in the queue details box in the UI.

{quote } Agree {quote}

> Capacity Scheduler: Support Auto Creation of Leaf Queues While Doing Queue Mapping
> ----------------------------------------------------------------------------------
>                 Key: YARN-7117
>                 URL: https://issues.apache.org/jira/browse/YARN-7117
>             Project: Hadoop YARN
>          Issue Type: New Feature
>          Components: capacity scheduler
>            Reporter: Wangda Tan
>            Assignee: Wangda Tan
>         Attachments: YARN-7117.Capacity.Scheduler.Support.Auto.Creation.Of.Leaf.Queue.pdf
> Currently Capacity Scheduler doesn't support auto creation of queues when doing queue
mapping. We saw more and more use cases which has complex queue mapping policies configured
to handle application to queues mapping. 
> The most common use case of CapacityScheduler queue mapping is to create one queue for
each user/group. However update {{capacity-scheduler.xml}} and {{RMAdmin:refreshQueues}} needs
to be done when new user/group onboard. One of the option to solve the problem is automatically
create queues when new user/group arrives.

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