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https://issues.apache.org/jira/browse/MAPREDUCE-893?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12756446#action_12756446
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Vinod K V commented on MAPREDUCE-893:
-------------------------------------
Also, for those who are listening, this is the new QueueRefresher interface
that I am adding to TaskScheduler:
{code}
abstract class TaskScheduler implements Configurable {
......
......
/**
* Abstract QueueRefresher class. Scheduler's can extend this and return an
* instance of this in the {...@link #getQueueRefresher()} method. The
* {...@link #refreshQueues(List)} method of this instance will be invoked by
the
* {...@link QueueManager} whenever it gets a request from an administrator to
* refresh its own queue-configuration. This method has a documented contract
* between the {...@link QueueManager} and the {...@link TaskScheduler}.
*/
abstract class QueueRefresher {
/**
* Refresh the queue-configuration in the scheduler. This method has the
* following contract.
* <ol>
* <li>Before this method, {...@link QueueManager} does a validation of the
new
* queue-configuration. For e.g, currently addition of new queues, or
* removal of queues at any level in the hierarchy is not supported by
* {...@link QueueManager} and so are not supported for schedulers too.</li>
* <li>Schedulers will be passed a list of {...@link JobQueueInfo}s of the
root
* queues i.e. the queues at the top level. All the descendants are properly
* linked from these top-level queues.</li>
* <li>Schedulers should use the scheduler specific queue properties from
* the newRootQueues, validate the properties themselves and apply them
* internally.</li>
* <li>
* Once the method returns successfully from the schedulers, it is assumed
* that the refresh of queue properties is successful throughout and will be
* 'committed' internally to {...@link QueueManager} too. It is guaranteed
that
* at no point, after successful return from the scheduler, is the queue
* refresh in QueueManager failed. If ever, such abnormalities happen, the
* queue framework will be inconsistent and will need a JT restart.</li>
* <li>If scheduler throws an exception during {...@link #refreshQueues()},
* {...@link QueueManager} throws away the newly read configuration, retains
* the old (consistent) configuration and informs the request issuer about
* the error appropriately.</li>
* </ol>
*
* @param newRootQueues
*/
abstract void refreshQueues(List<JobQueueInfo> newRootQueues)
throws Throwable;
}
/**
* Get the {...@link QueueRefresher} for this scheduler. By default, no
* {...@link QueueRefresher} exists for a scheduler and is set to null.
* Schedulers need to return an instance of {...@link QueueRefresher} if they
* wish to refresh their queue-configuration when {...@link QueueManager}
* refreshes its own queue-configuration via an administrator request.
*
* @return
*/
QueueRefresher getQueueRefresher() {
return null;
}
}
{code}
> Provide an ability to refresh queue configuration without restart.
> ------------------------------------------------------------------
>
> Key: MAPREDUCE-893
> URL: https://issues.apache.org/jira/browse/MAPREDUCE-893
> Project: Hadoop Map/Reduce
> Issue Type: Improvement
> Components: jobtracker
> Reporter: Hemanth Yamijala
> Assignee: Vinod K V
> Fix For: 0.21.0
>
> Attachments: MAPREDUCE-893-20090915.1.txt,
> MAPREDUCE-893-20090917.2.txt
>
>
> While administering a cluster using multiple queues, administrators feel a
> need to refresh queue properties on the fly without needing to restart the
> JobTracker. This is partially supported for some properties such as queue
> ACLs (HADOOP-5396) and state (HADOOP-5913). The idea is to extend the
> facility to refresh other queue properties as well, including scheduler
> properties.
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