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From "Sandy Ryza (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (YARN-596) In fair scheduler, intra-application container priorities affect inter-application preemption decisions
Date Wed, 26 Mar 2014 22:38:15 GMT

    [ https://issues.apache.org/jira/browse/YARN-596?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13948574#comment-13948574
] 

Sandy Ryza commented on YARN-596:
---------------------------------

Thanks for working on this, Wei.

{code}
+    // Collect running containers from over-scheduled queues
+    Map<RMContainer, FSSchedulerApp> apps =
+        new HashMap<RMContainer, FSSchedulerApp>();
+    Map<RMContainer, FSLeafQueue> queues =
+        new HashMap<RMContainer, FSLeafQueue>();
+    for (FSLeafQueue sched : scheduler.getQueueManager().getLeafQueues()) {
+      if (Resources.greaterThan(RESOURCE_CALCULATOR, clusterCapacity,
+          sched.getResourceUsage(), sched.getFairShare())) {
+        for (AppSchedulable as : sched.getRunnableAppSchedulables()) {
+          for (RMContainer c : as.getApp().getLiveContainers()) {
+            apps.put(c, as.getApp());
+            queues.put(c, sched);
+          }
+        }
+      }
+    }
{code}

Do we still need this anymore?  If we're not collecting the running containers here, it seems
a little weird to build up the container->app/queue maps here.  We should be able to look
up the application attempt and corresponding queue with data that the RMContainer has, using
Fair Scheduler data structures.  Or return them with preemptContainer.

Can we rename FSPreemption to FairSchedulerPreemptor or just Preemptor?

What's the reasoning for cloneQueueApps and not just traversing the existing queues?

> In fair scheduler, intra-application container priorities affect inter-application preemption
decisions
> -------------------------------------------------------------------------------------------------------
>
>                 Key: YARN-596
>                 URL: https://issues.apache.org/jira/browse/YARN-596
>             Project: Hadoop YARN
>          Issue Type: Bug
>          Components: scheduler
>    Affects Versions: 2.0.3-alpha
>            Reporter: Sandy Ryza
>            Assignee: Sandy Ryza
>         Attachments: YARN-596.patch, YARN-596.patch, YARN-596.patch
>
>
> In the fair scheduler, containers are chosen for preemption in the following way:
> All containers for all apps that are in queues that are over their fair share are put
in a list.
> The list is sorted in order of the priority that the container was requested in.
> This means that an application can shield itself from preemption by requesting it's containers
at higher priorities, which doesn't really make sense.
> Also, an application that is not over its fair share, but that is in a queue that is
over it's fair share is just as likely to have containers preempted as an application that
is over its fair share.



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