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From "Weiwei Yang (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (YARN-8958) Schedulable entities leak in fair ordering policy when recovering containers between remove app attempt and remove app
Date Thu, 01 Nov 2018 02:49:00 GMT

    [ https://issues.apache.org/jira/browse/YARN-8958?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16671044#comment-16671044
] 

Weiwei Yang commented on YARN-8958:
-----------------------------------

Hi [~Tao Yang], No worries. I saw it several times, it should not be caused by this patch.

I think the fix makes sense to me, I'll take one more look today. Thanks

> Schedulable entities leak in fair ordering policy when recovering containers between
remove app attempt and remove app
> ----------------------------------------------------------------------------------------------------------------------
>
>                 Key: YARN-8958
>                 URL: https://issues.apache.org/jira/browse/YARN-8958
>             Project: Hadoop YARN
>          Issue Type: Bug
>          Components: capacityscheduler
>    Affects Versions: 3.2.1
>            Reporter: Tao Yang
>            Assignee: Tao Yang
>            Priority: Major
>         Attachments: YARN-8958.001.patch, YARN-8958.002.patch
>
>
> We found a NPE in ClientRMService#getApplications when querying apps with specified queue.
The cause is that there is one app which can't be found by calling RMContextImpl#getRMApps(is
finished and swapped out of memory) but still can be queried from fair ordering policy.
> To reproduce schedulable entities leak in fair ordering policy:
> (1) create app1 and launch container1 on node1
> (2) restart RM
> (3) remove app1 attempt, app1 is removed from the schedulable entities.
> (4) recover container1 after node1 reconnected to RM, then the state of contianer1 is
changed to COMPLETED, app1 is bring back to entitiesToReorder after container released, then
app1 will be added back into schedulable entities after calling FairOrderingPolicy#getAssignmentIterator
by scheduler.
> (5) remove app1
> To solve this problem, we should make sure schedulableEntities can only be affected by
add or remove app attempt, new entity should not be added into schedulableEntities by reordering
process.
> {code:java}
>   protected void reorderSchedulableEntity(S schedulableEntity) {
>     //remove, update comparable data, and reinsert to update position in order
>     schedulableEntities.remove(schedulableEntity);
>     updateSchedulingResourceUsage(
>       schedulableEntity.getSchedulingResourceUsage());
>     schedulableEntities.add(schedulableEntity);
>   }
> {code}
> Related codes above can be improved as follow to make sure only existent entity can be
re-add into schedulableEntities.
> {code:java}
>   protected void reorderSchedulableEntity(S schedulableEntity) {
>     //remove, update comparable data, and reinsert to update position in order
>     boolean exists = schedulableEntities.remove(schedulableEntity);
>     updateSchedulingResourceUsage(
>       schedulableEntity.getSchedulingResourceUsage());
>     if (exists) {
>       schedulableEntities.add(schedulableEntity);
>     } else {
>       LOG.info("Skip reordering non-existent schedulable entity: "
>           + schedulableEntity.getId());
>     }
>   }
> {code}



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