输出、状态-hadoop源码TaskAttemptID TaskTrackerAction JobTracker，FileOutputCommitter相关-by小雨

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    1,TaskAttemptID代表task attempt，一个task attempt就是一个map/reduce task 的一个例实taskid，而个每TaskAttemptID由两部分构成：TaskID+task序列号

    eg:

    attempt_200707121733_0003_m_000005_0

    代表2007年07月12日17点33分启动的第0003号作业（job）的第00005号map任务的第0号task attempt

    2,TaskTrackerAction的类型有，LaunchTaskAction()，KillTaskAction()，KillJobAction()，ReinitTrackerAction()，CommitTaskAction();

 /**
   * Ennumeration of various 'actions' that the {@link JobTracker}
   * directs the {@link TaskTracker} to perform periodically.
   *
   */
  public static enum ActionType {
    /** Launch a new task. */
    LAUNCH_TASK,
    
    /** Kill a task. */
    KILL_TASK,
    
    /** Kill any tasks of this job and cleanup. */
    KILL_JOB,
    
    /** Reinitialize the tasktracker. */
    REINIT_TRACKER,

    /** Ask a task to save its output. */
    COMMIT_TASK
  };
 
  /**
   * A factory-method to create objects of given {@link ActionType}.
   * @param actionType the {@link ActionType} of object to create.
   * @return an object of {@link ActionType}.
   */
  public static TaskTrackerAction createAction(ActionType actionType) {
    TaskTrackerAction action = null;
    
    switch (actionType) {
    case LAUNCH_TASK:
      {
        action = new LaunchTaskAction();
      }
      break;
    case KILL_TASK:
      {
        action = new KillTaskAction();
      }
      break;
    case KILL_JOB:
      {
        action = new KillJobAction();
      }
      break;
    case REINIT_TRACKER:
      {
        action = new ReinitTrackerAction();
      }
      break;
    case COMMIT_TASK:
      {
        action = new CommitTaskAction();
      }
      break;
    }

    return action;
  }

    3,JobTracker中相干：

           offerService()

                       |--taskScheduler.start();

                       |--recoveryManager.recover();

    通过RecoveryManager的recover()法方恢复Job

                       |-- this.expireTrackersThread.start();

    检测已失效的TaskTracker点节。

    // Used to expire TaskTrackers that have gone down

                       |-- this.retireJobsThread.start();

    除清那些已成完很长时光仍然存在队列中的job

                       |--expireLaunchingTaskThread.start();

    停止那些在超时时光内未告报进度的Tasks。

    A thread to timeout tasks that have been assigned to task trackers,
   * but that haven't reported back yet.

                       |--completedJobsStoreThread.start();

                       |--this.interTrackerServer.start();/ start the inter-tracker server once the jt is ready
 

      /**
   * Run forever
   */
  public void offerService() throws InterruptedException, IOException {
    // Prepare for recovery. This is done irrespective of the status of restart
    // flag.
    while (true) {
      try {
        recoveryManager.updateRestartCount();
        break;
      } catch (IOException ioe) {
        LOG.warn("Failed to initialize recovery manager. ", ioe);
        // wait for some time
        Thread.sleep(FS_ACCESS_RETRY_PERIOD);
        LOG.warn("Retrying...");
      }
    }

    taskScheduler.start();
    
    //  Start the recovery after starting the scheduler
    try {
      recoveryManager.recover();
    } catch (Throwable t) {
      LOG.warn("Recovery manager crashed! Ignoring.", t);
    }
    
    this.expireTrackersThread = new Thread(this.expireTrackers,
                                          "expireTrackers");
    this.expireTrackersThread.start();
    this.retireJobsThread = new Thread(this.retireJobs, "retireJobs");
    this.retireJobsThread.start();
    expireLaunchingTaskThread.start();

    if (completedJobStatusStore.isActive()) {
      completedJobsStoreThread = new Thread(completedJobStatusStore,
                                            "completedjobsStore-housekeeper");
      completedJobsStoreThread.start();
    }

    // start the inter-tracker server once the jt is ready
    this.interTrackerServer.start();
    
    synchronized (this) {
      state = State.RUNNING;
    }

    4, Job的五种状态

 public static final int RUNNING = 1;
  public static final int SUCCEEDED = 2;
  public static final int FAILED = 3;
  public static final int PREP = 4;

  public static final int KILLED = 5;

    

    5，jobStatus信息:

  this.jobid = jobid;
     this.setupProgress = setupProgress;
     this.mapProgress = mapProgress;
     this.reduceProgress = reduceProgress;
     this.cleanupProgress = cleanupProgress;
     this.runState = runState;

    6，FileOutputCommitter相干

    setupJob：Hadoop初始化时设置job的输出；

    commitJob：当job成完时，除清job的输出，这个法方在馈反来回的job状态为SUCCEEDED时用调；

    cleanupJob：job结束后除清job的输出；

     // do the clean up of temporary directory

    abortJob：当job的返回状态是FAILED或KILLED时，行执该数函，用于终止作业的输出；

    setupTask：设置task的输出；

    // FileOutputCommitter's setupTask doesn't do anything. Because the
       // temporary task directory is created on demand when the
       // task is writing.

    needsTaskCommit：检测task否是须要交提；

    commitTask：将task的输出移到作业的输出目录；

    // Move the task outputs to their final place

    // Delete the temporary task-specific output directory

    abortTask：取消task的输出；

    

     

    

    

    

    

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