[jira] [Updated] (YARN-6210) FS: Node reservations can interfere with preemption

["Karthik Kambatla (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/YARN-6210?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Karthik Kambatla updated YARN-6210:
-----------------------------------
    Attachment: YARN-6210.1.patch

Patch (v1) does the following:
# Only starved apps can reserve nodes
# The starvation check considers a single resource. For instance, in the case of DRF, this corresponds to the dominant resource: (1) the app is considered starved if it is starved on the dominant resource, (2) an app can be preempted as long as it is not starved on the dominant resource. 
# FSAppAttempt#toString for easier debugging of tests
# DominantResourceFairnessComparator#compare can return 0 if the submit time is the same. This leads to issues while allocating containers. Changed this to be in line with FairShareComparator and return either -1 or 1.
# Added the test from YARN-6151. FYI. [~yufeigu]

> FS: Node reservations can interfere with preemption
> ---------------------------------------------------
>
>                 Key: YARN-6210
>                 URL: https://issues.apache.org/jira/browse/YARN-6210
>             Project: Hadoop YARN
>          Issue Type: Bug
>          Components: fairscheduler
>    Affects Versions: 2.9.0
>            Reporter: Karthik Kambatla
>            Assignee: Karthik Kambatla
>         Attachments: YARN-6210.1.patch
>
>
> Today, on a saturated cluster, apps with pending demand reserve nodes. A new app might not be able to preempt resources because these nodes are already reserved. This can be reproduced by the example in YARN-6151. 
> Since node reservations are to prevent starvation of apps requesting large containers, triggering these reservations only on starved applications would avoid this situation. 



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