org.apache.hadoop.mapred.TaskScheduler 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.io.IOException;
import java.util.Collection;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import org.apache.hadoop.conf.Configurable;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.mapreduce.TaskType;
import org.apache.hadoop.mapreduce.server.jobtracker.TaskTracker;
/**
* Used by a {@link JobTracker} to schedule {@link Task}s on
* {@link TaskTracker}s.
*
* {@link TaskScheduler}s typically use one or more
* {@link JobInProgressListener}s to receive notifications about jobs.
*
* 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 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 getJobs(String queueName);
/**
* Obtain the total number of slots for the tasktracker.
* @param status The status of the tasktracker
* @param type The task type we want to know about the capacity
* @return The number of total slots on the tasktracker.
*/
public int getMaxSlots(TaskTrackerStatus status, TaskType type) {
return type == TaskType.MAP ?
status.getMaxMapSlots() : status.getMaxReduceSlots();
}
/**
* Returns a user readable string about the scheduling status of a job
* @param job The job to query
* @return The schedule information of the job
*/
public String jobScheduleInfo(JobInProgress job) {
return "n/a";
}
/**
* Is this job configuration valid?
* @param job Job to check
* @throws InvalidJobConfException When the configuration is not valid
*/
public void checkJob(JobInProgress job) throws InvalidJobConfException {
// do nothing
}
}