| /** |
| * 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 org.apache.hadoop.conf.Configurable; |
| import org.apache.hadoop.conf.Configuration; |
| import org.apache.hadoop.mapreduce.server.jobtracker.TaskTracker; |
| |
| /** |
| * A pluggable object for selecting tasks to run from a {@link JobInProgress} on |
| * a given {@link TaskTracker}, for use by the {@link TaskScheduler}. The |
| * <code>TaskSelector</code> is in charge of managing both locality and |
| * speculative execution. For the latter purpose, it must also provide counts of |
| * how many tasks each speculative job needs to launch, so that the scheduler |
| * can take this into account in its calculations. |
| */ |
| public abstract class TaskSelector 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 TaskSelector to start any work in separate |
| * threads. |
| */ |
| public void start() throws IOException { |
| // do nothing |
| } |
| |
| /** |
| * Lifecycle method to allow the TaskSelector to stop any work it is doing. |
| */ |
| public void terminate() throws IOException { |
| // do nothing |
| } |
| |
| /** |
| * How many speculative map tasks does the given job want to launch? |
| * @param job The job to count speculative maps for |
| * @return Number of speculative maps that can be launched for job |
| */ |
| public abstract int neededSpeculativeMaps(JobInProgress job); |
| |
| /** |
| * How many speculative reduce tasks does the given job want to launch? |
| * @param job The job to count speculative reduces for |
| * @return Number of speculative reduces that can be launched for job |
| */ |
| public abstract int neededSpeculativeReduces(JobInProgress job); |
| |
| /** |
| * Choose a map task to run from the given job on the given TaskTracker. |
| * @param taskTracker {@link TaskTrackerStatus} of machine to run on |
| * @param job Job to select a task for |
| * @return A {@link Task} to run on the machine, or <code>null</code> if |
| * no map should be launched from this job on the task tracker. |
| * @throws IOException |
| */ |
| public abstract Task obtainNewMapTask(TaskTrackerStatus taskTracker, |
| JobInProgress job, int localityLevel) throws IOException; |
| |
| /** |
| * Choose a reduce task to run from the given job on the given TaskTracker. |
| * @param taskTracker {@link TaskTrackerStatus} of machine to run on |
| * @param job Job to select a task for |
| * @return A {@link Task} to run on the machine, or <code>null</code> if |
| * no reduce should be launched from this job on the task tracker. |
| * @throws IOException |
| */ |
| public abstract Task obtainNewReduceTask(TaskTrackerStatus taskTracker, |
| JobInProgress job) throws IOException; |
| } |