org.apache.hadoop.mapred.QueueRefresher Maven / Gradle / Ivy
/**
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.hadoop.mapred;
import java.util.List;
/**
* 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}.
*
* Before calling QueueRefresher, the caller must hold the lock to the
* corresponding {@link TaskScheduler} (generally in the {@link JobTracker}).
*/
abstract class QueueRefresher {
/**
* Refresh the queue-configuration in the scheduler. This method has the
* following contract.
*
* - 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.
* - 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.
* - Schedulers should use the scheduler specific queue properties from
* the newRootQueues, validate the properties themselves and apply them
* internally.
* -
* 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.
* - 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.
*
*
* @param newRootQueues
*/
abstract void refreshQueues(List newRootQueues)
throws Throwable;
}