| /** |
| * 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.io.IOException; |
| import java.util.Collection; |
| import java.util.List; |
| |
| import org.apache.hadoop.conf.Configurable; |
| import org.apache.hadoop.conf.Configuration; |
| import org.apache.hadoop.mapreduce.server.jobtracker.TaskTracker; |
| |
| /** |
| * Used by a {@link JobTracker} to schedule {@link Task}s on |
| * {@link TaskTracker}s. |
| * <p> |
| * {@link TaskScheduler}s typically use one or more |
| * {@link JobInProgressListener}s to receive notifications about jobs. |
| * <p> |
| * It is the responsibility of the {@link TaskScheduler} |
| * to initialize tasks for a job, by calling {@link JobInProgress#initTasks()} |
| * between the job being added (when |
| * {@link JobInProgressListener#jobAdded(JobInProgress)} is called) |
| * and tasks for that job being assigned (by |
| * {@link #assignTasks(TaskTracker)}). |
| * @see EagerTaskInitializationListener |
| */ |
| abstract class TaskScheduler implements Configurable { |
| |
| protected Configuration conf; |
| protected TaskTrackerManager taskTrackerManager; |
| |
| public Configuration getConf() { |
| return conf; |
| } |
| |
| public void setConf(Configuration conf) { |
| this.conf = conf; |
| } |
| |
| public synchronized void setTaskTrackerManager( |
| TaskTrackerManager taskTrackerManager) { |
| this.taskTrackerManager = taskTrackerManager; |
| } |
| |
| /** |
| * Lifecycle method to allow the scheduler to start any work in separate |
| * threads. |
| * @throws IOException |
| */ |
| public void start() throws IOException { |
| // do nothing |
| } |
| |
| /** |
| * Lifecycle method to allow the scheduler to stop any work it is doing. |
| * @throws IOException |
| */ |
| public void terminate() throws IOException { |
| // do nothing |
| } |
| |
| /** |
| * Returns the tasks we'd like the TaskTracker to execute right now. |
| * |
| * @param taskTracker The TaskTracker for which we're looking for tasks. |
| * @return A list of tasks to run on that TaskTracker, possibly empty. |
| */ |
| public abstract List<Task> assignTasks(TaskTracker taskTracker) |
| throws IOException; |
| |
| /** |
| * Returns a collection of jobs in an order which is specific to |
| * the particular scheduler. |
| * @param queueName |
| * @return |
| */ |
| public abstract Collection<JobInProgress> getJobs(String queueName); |
| |
| /** |
| * 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; |
| } |
| |
| /** |
| * 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; |
| } |
| } |