JobQueueJobInProgressListener

JobQueueJobInProgressListener继承自抽象类JobInprogressListener

/** * 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;/** * A listener for changes in a {@link JobInProgress job}'s lifecycle in the * {@link JobTracker}. */abstract class JobInProgressListener {  /**   * Invoked when a new job has been added to the {@link JobTracker}.   * @param job The added job.   * @throws IOException    */  public abstract void jobAdded(JobInProgress job) throws IOException;  /**   * Invoked when a job has been removed from the {@link JobTracker}.   * @param job The removed job.   */  public abstract void jobRemoved(JobInProgress job);    /**   * Invoked when a job has been updated in the {@link JobTracker}.   * This change in the job is tracker using {@link JobChangeEvent}.   * @param event the event that tracks the change   */  public abstract void jobUpdated(JobChangeEvent event);}

主要是三个方法，jobAdded,jobRemoved,jobUpdated分别对应作业添加，删除和更新。

/** * 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.Collection;import java.util.Collections;import java.util.Comparator;import java.util.Map;import java.util.TreeMap;import org.apache.hadoop.mapred.JobStatusChangeEvent.EventType;/** * A {@link JobInProgressListener} that maintains the jobs being managed in * a queue. By default the queue is FIFO, but it is possible to use custom * queue ordering by using the * {@link #JobQueueJobInProgressListener(Collection)} constructor. */class JobQueueJobInProgressListener extends JobInProgressListener {  /** A class that groups all the information from a {@link JobInProgress} that    * is necessary for scheduling a job.   */   static class JobSchedulingInfo {    private JobPriority priority;    private long startTime;    private JobID id;        public JobSchedulingInfo(JobInProgress jip) {      this(jip.getStatus());    }        public JobSchedulingInfo(JobStatus status) {      priority = status.getJobPriority();      startTime = status.getStartTime();      id = status.getJobID();    }        JobPriority getPriority() {return priority;}    long getStartTime() {return startTime;}    JobID getJobID() {return id;}        @Override    public boolean equals(Object obj) {      if (obj == null || obj.getClass() != JobSchedulingInfo.class) {        return false;      } else if (obj == this) {        return true;      }      else if (obj instanceof JobSchedulingInfo) {        JobSchedulingInfo that = (JobSchedulingInfo)obj;        return (this.id.equals(that.id) &&                 this.startTime == that.startTime &&                 this.priority == that.priority);      }      return false;    }    @Override    public int hashCode() {      return (int)(id.hashCode() * priority.hashCode() + startTime);    }  }    static final Comparator<JobSchedulingInfo> FIFO_JOB_QUEUE_COMPARATOR    = new Comparator<JobSchedulingInfo>() {    public int compare(JobSchedulingInfo o1, JobSchedulingInfo o2) {      int res = o1.getPriority().compareTo(o2.getPriority());      if (res == 0) {        if (o1.getStartTime() < o2.getStartTime()) {          res = -1;        } else {          res = (o1.getStartTime() == o2.getStartTime() ? 0 : 1);        }      }      if (res == 0) {        res = o1.getJobID().compareTo(o2.getJobID());      }      return res;    }  };    private Map<JobSchedulingInfo, JobInProgress> jobQueue;    public JobQueueJobInProgressListener() {    this(new TreeMap<JobSchedulingInfo,                      JobInProgress>(FIFO_JOB_QUEUE_COMPARATOR));  }  /**   * For clients that want to provide their own job priorities.   * @param jobQueue A collection whose iterator returns jobs in priority order.   */  protected JobQueueJobInProgressListener(Map<JobSchedulingInfo,                                           JobInProgress> jobQueue) {    this.jobQueue = Collections.synchronizedMap(jobQueue);  }  /**   * Returns a synchronized view of the job queue.   */  public Collection<JobInProgress> getJobQueue() {    return jobQueue.values();  }    @Override  public void jobAdded(JobInProgress job) {    jobQueue.put(new JobSchedulingInfo(job.getStatus()), job);  }  // Job will be removed once the job completes  @Override  public void jobRemoved(JobInProgress job) {}    private void jobCompleted(JobSchedulingInfo oldInfo) {    jobQueue.remove(oldInfo);  }    @Override  public synchronized void jobUpdated(JobChangeEvent event) {    JobInProgress job = event.getJobInProgress();    if (event instanceof JobStatusChangeEvent) {      // Check if the ordering of the job has changed      // For now priority and start-time can change the job ordering      JobStatusChangeEvent statusEvent = (JobStatusChangeEvent)event;      JobSchedulingInfo oldInfo =          new JobSchedulingInfo(statusEvent.getOldStatus());      if (statusEvent.getEventType() == EventType.PRIORITY_CHANGED           || statusEvent.getEventType() == EventType.START_TIME_CHANGED) {        // Make a priority change        reorderJobs(job, oldInfo);      } else if (statusEvent.getEventType() == EventType.RUN_STATE_CHANGED) {        // Check if the job is complete        int runState = statusEvent.getNewStatus().getRunState();        if (runState == JobStatus.SUCCEEDED            || runState == JobStatus.FAILED            || runState == JobStatus.KILLED) {          jobCompleted(oldInfo);        }      }    }  }    private void reorderJobs(JobInProgress job, JobSchedulingInfo oldInfo) {    synchronized (jobQueue) {      jobQueue.remove(oldInfo);      jobQueue.put(new JobSchedulingInfo(job), job);    }  }}

JobQueueJobInprogressListener定义了一个类JobSchedulingInfo用来保存Job的优先级，开始时间，id信息，这三个信息用于确定作业在作业队列中的先后顺序。作业队列即为成员变量 private Map<JobSchedulingInfo, JobInProgress> jobQueue。

  public JobQueueJobInProgressListener() {    this(new TreeMap<JobSchedulingInfo,                      JobInProgress>(FIFO_JOB_QUEUE_COMPARATOR));  }  /**   * For clients that want to provide their own job priorities.   * @param jobQueue A collection whose iterator returns jobs in priority order.   */  protected JobQueueJobInProgressListener(Map<JobSchedulingInfo,                                           JobInProgress> jobQueue) {    this.jobQueue = Collections.synchronizedMap(jobQueue);  }

可见在默认构造方法中调用了一个带有参数的构造函数，传入的参数是一个带有比较器的map，而在被调用的带参数的构造函数中jobQueue被初始化，最终jobQueue是一个带有比较器的队列。

另外重写了jobAdded,jobRemoved,jobUpdated方法。jobAdded方法实现比较简单，jobRemoved方法其实什么也不做，它的功能被jobCompleted方法取代，在jobUpdated中，其逻辑是先判断事件类型，如果是变更了优先级等信息，则重新对队列排队，如果是作业运行成功，失败或者作业被杀死，则将作业从队列中删除。