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From "Wilfred Spiegelenburg (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (YARN-8191) Fair scheduler: queue deletion without RM restart
Date Mon, 07 May 2018 05:07:00 GMT

    [ https://issues.apache.org/jira/browse/YARN-8191?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16465436#comment-16465436
] 

Wilfred Spiegelenburg commented on YARN-8191:
---------------------------------------------

thank you for the updated patch:
 * In {{removeEmptyDynamicQueues}} why are we not using {{getLeafQueues}} instead of {{getQueues}}?
The queue cleanup should start with the leafs and it removes the need to check if the queue
has children.
 * In {{removeEmptyDynamicQueues}} instead of adding to parentQueuesToCheck without checks
should we not only add a parent queue if that queue is dynamic? That also removes the need
for the root queue check while iterating and the only check for child queues is needed.
 * In {{updateAllocationConfiguration}} there should be no need to go over all the queues
and set the isDynamic flag. The flag should be set on creation and never updated after that
unless it was an incompatible queue. We should add a new getLeafQueue and getParentQueue
method which takes the isDynamic flag and sets it. It then can call the existing method. The
only place that we would call the new method would be in {{updateAllocationConfiguration}}.
The old version of the method would stay as is as the isDynamic flag set to {{true}} by default.
That should handle all placement rules etc.
* To clean up any removed configured, non dynamic, queues we need to be smart and we do not
want to walk over all queues. In {{onReload}} we have the old and new configured queues and
we can easily build a list of queues which need to become dynamic:
{code}
Set<String> toDynamic = new HashSet<>();
if (queueInfo != null) {
  toDynamic.addAll(allocConf.getConfiguredQueues().get(FSQueueType.LEAF));
  toDynamic.addAll(allocConf.getConfiguredQueues().get(FSQueueType.PARENT));
  toDynamic.removeAll(queueInfo.configuredQueues.get(FSQueueType.LEAF));
  toDynamic.removeAll(queueInfo.configuredQueues.get(FSQueueType.PARENT));
}
if (!toDynamic.isEmpty()) {
  queueMgr.changeToDynamic(toDynamic);
}
{code}
The {{changeToDynamic}} just needs to walk over the set and set the flag. The standard cleanup
code for the dynamic queues will then take care of the cleanup without needing lots of iterations.
Building this diff of queues can happen outside of locking in the FS.
 * The logic behind {{getDynamicQueueNames}} is not correct: the configuredQueues set as stored
in the AllocationConfiguration only has queues that are defined in the configuration. There
can never be a dynamic queue in that list. Dynamic queues can only be created via the placement
rules. (see previous comments)
 * As a side node: {{getLeafQueues}} in the QueueManager should return an ImmutableList of
the leaf queues like we do in {{getQueues}}

> Fair scheduler: queue deletion without RM restart
> -------------------------------------------------
>
>                 Key: YARN-8191
>                 URL: https://issues.apache.org/jira/browse/YARN-8191
>             Project: Hadoop YARN
>          Issue Type: Improvement
>          Components: fairscheduler
>    Affects Versions: 3.0.1
>            Reporter: Gergo Repas
>            Assignee: Gergo Repas
>            Priority: Major
>         Attachments: Queue Deletion in Fair Scheduler.pdf, YARN-8191.000.patch, YARN-8191.001.patch,
YARN-8191.002.patch, YARN-8191.003.patch, YARN-8191.004.patch, YARN-8191.005.patch
>
>
> The Fair Scheduler never cleans up queues even if they are deleted in the allocation
file, or were dynamically created and are never going to be used again. Queues always remain
in memory which leads to two following issues.
>  # Steady fairshares aren’t calculated correctly due to remaining queues
>  # WebUI shows deleted queues, which is confusing for users (YARN-4022).
> We want to support proper queue deletion without restarting the Resource Manager:
>  # Static queues without any entries that are removed from fair-scheduler.xml should
be deleted from memory.
>  # Dynamic queues without any entries should be deleted.
>  # RM Web UI should only show the queues defined in the scheduler at that point in time.



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