[jira] [Updated] (YARN-2362) Capacity Scheduler: apps with requests that exceed current capacity can starve pending apps

["Ram Venkatesh (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/YARN-2362?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Ram Venkatesh updated YARN-2362:
--------------------------------

    Summary: Capacity Scheduler: apps with requests that exceed current capacity can starve pending apps  (was: Capacity Scheduler: apps with requests that exceed capacity can starve pending apps)

> Capacity Scheduler: apps with requests that exceed current capacity can starve pending apps
> -------------------------------------------------------------------------------------------
>
>                 Key: YARN-2362
>                 URL: https://issues.apache.org/jira/browse/YARN-2362
>             Project: Hadoop YARN
>          Issue Type: Bug
>          Components: capacityscheduler
>    Affects Versions: 2.4.1
>            Reporter: Ram Venkatesh
>
> Cluster configuration:
> Total memory: 8GB
> yarn.scheduler.minimum-allocation-mb 256
> yarn.scheduler.capacity.maximum-am-resource-percent 1 (100%, test only config)
> App 1 makes a request for 4.6 GB, succeeds, app transitions to RUNNING state. It subsequently makes a request for 4.6 GB, which cannot be granted and it waits.
> App 2 makes a request for 1 GB - never receives it, so the app stays in the ACCEPTED state for ever.
> I think this can happen in leaf queues that are near capacity.
> The fix is likely in LeafQueue.java assignContainers near line 861, where it returns if the assignment would exceed queue capacity, instead of checking if requests for other active applications can be met.
> {code:title=LeafQueue.java|borderStyle=solid}
>            // Check queue max-capacity limit
>            if (!assignToQueue(clusterResource, required)) {
> -            return NULL_ASSIGNMENT;
> +            break;
>            }
> {code}
> With this change, the scenario above allows App 2 to start and finish while App 1 continues to wait.
> I have a patch available, but wondering if the current behavior is by design.



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