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From "Zian Chen (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (YARN-8379) Add an option to allow Capacity Scheduler preemption to balance satisfied queues
Date Tue, 26 Jun 2018 00:10:00 GMT

    [ https://issues.apache.org/jira/browse/YARN-8379?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16522977#comment-16522977

Zian Chen commented on YARN-8379:

[~eepayne], for the suggestions you mentioned before which is make the balancing was done
all at once instead of add FifoSelector twice. Let me explain this in two aspects,

1. in TempQueuePerPartition#offer. When we calculate ideal assignment, first time we calculate
accepted using this,
// accepted = min{avail,
//               max - assigned,
//               current + pending - assigned,
//               # Make sure a queue will not get more than max of its
//               # used/guaranteed, this is to make sure preemption won't
//               # happen if all active queues are beyond their guaranteed
//               # This is for leaf queue only.
//               max(guaranteed, used) - assigned}
The second time, we calculate accepted without check max(guaranteed, used), as far as I can
see, this two steps should be done sequentially instead of in one shot.
2. Another reason is we add an option to set configureable timeout for preempt-to-balance
selected containers (selected by fifo2) which can let user set custom timeout for these preempt-to-balance
containers and actually kill them faster/slower based on user needs, which leads to control
the balance process to be faster or slower. But this timeout should only be affects containers
selected for balance, not for an underutilized queue to reach its guaranteed resource. So
we need to separate these two process.
All other comments should be handled by the latest patch already. Thanks!

> Add an option to allow Capacity Scheduler preemption to balance satisfied queues
> --------------------------------------------------------------------------------
>                 Key: YARN-8379
>                 URL: https://issues.apache.org/jira/browse/YARN-8379
>             Project: Hadoop YARN
>          Issue Type: Bug
>            Reporter: Wangda Tan
>            Assignee: Zian Chen
>            Priority: Major
>         Attachments: YARN-8379.001.patch, YARN-8379.002.patch, YARN-8379.003.patch, YARN-8379.004.patch,
> Existing capacity scheduler only supports preemption for an underutilized queue to reach
its guaranteed resource. In addition to that, there’s an requirement to get better balance
between queues when all of them reach guaranteed resource but with different fairness resource.
> An example is, 3 queues with capacity, queue_a = 30%, queue_b = 30%, queue_c = 40%. At
time T. queue_a is using 30%, queue_b is using 70%. Existing scheduler preemption won't happen.
But this is unfair to queue_a since queue_a has the same guaranteed resources.
> Before YARN-5864, capacity scheduler do additional preemption to balance queues. We changed
the logic since it could preempt too many containers between queues when all queues are satisfied.

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