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From "Varun Vasudev (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (YARN-2628) Capacity scheduler with DominantResourceCalculator carries out reservation even though slots are free
Date Wed, 01 Oct 2014 22:38:37 GMT

     [ https://issues.apache.org/jira/browse/YARN-2628?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Varun Vasudev updated YARN-2628:
--------------------------------
    Attachment: apache-yarn-2628.1.patch

Uploaded a patch to address [~jianhe]'s comments.

> Capacity scheduler with DominantResourceCalculator carries out reservation even though
slots are free
> -----------------------------------------------------------------------------------------------------
>
>                 Key: YARN-2628
>                 URL: https://issues.apache.org/jira/browse/YARN-2628
>             Project: Hadoop YARN
>          Issue Type: Bug
>          Components: capacityscheduler
>    Affects Versions: 2.5.1
>            Reporter: Varun Vasudev
>            Assignee: Varun Vasudev
>         Attachments: apache-yarn-2628.0.patch, apache-yarn-2628.1.patch
>
>
> We've noticed that if you run the CapacityScheduler with the DominantResourceCalculator,
sometimes apps will end up with containers in a reserved state even though free slots are
available.
> The root cause seems to be this piece of code from CapacityScheduler.java -
> {noformat}
>     // Try to schedule more if there are no reservations to fulfill
>     if (node.getReservedContainer() == null) {
>       if (Resources.greaterThanOrEqual(calculator, getClusterResource(),
>           node.getAvailableResource(), minimumAllocation)) {
>         if (LOG.isDebugEnabled()) {
>           LOG.debug("Trying to schedule on node: " + node.getNodeName() +
>               ", available: " + node.getAvailableResource());
>         }
>         root.assignContainers(clusterResource, node, false);
>       }
>     } else {
>       LOG.info("Skipping scheduling since node " + node.getNodeID() + 
>           " is reserved by application " + 
>           node.getReservedContainer().getContainerId().getApplicationAttemptId()
>           );
>     }
> {noformat}
> The code is meant to check if a node has any slots available for containers . Since it
uses the greaterThanOrEqual function, we end up in situation where greaterThanOrEqual returns
true, even though we may not have enough CPU or memory to actually run the container.



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