| /** |
| * 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. |
| * <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; |
| } |
