Exemplo n.º 1
5
  /** Process incoming heartbeat messages from the task trackers. */
  public synchronized int emitHeartbeat(TaskTrackerStatus trackerStatus, boolean initialContact) {
    String trackerName = trackerStatus.getTrackerName();
    trackerStatus.setLastSeen(System.currentTimeMillis());

    synchronized (taskTrackers) {
      synchronized (trackerExpiryQueue) {
        boolean seenBefore = updateTaskTrackerStatus(trackerName, trackerStatus);
        if (initialContact) {
          // If it's first contact, then clear out any state hanging around
          if (seenBefore) {
            lostTaskTracker(trackerName);
          }
        } else {
          // If not first contact, there should be some record of the tracker
          if (!seenBefore) {
            return InterTrackerProtocol.UNKNOWN_TASKTRACKER;
          }
        }

        if (initialContact) {
          trackerExpiryQueue.add(trackerStatus);
        }
      }
    }

    updateTaskStatuses(trackerStatus);
    // LOG.info("Got heartbeat from "+trackerName);
    return InterTrackerProtocol.TRACKERS_OK;
  }
Exemplo n.º 2
0
 /**
  * Update the last recorded status for the given task tracker. It assumes that the taskTrackers
  * are locked on entry.
  *
  * @author Owen O'Malley
  * @param trackerName The name of the tracker
  * @param status The new status for the task tracker
  * @return Was an old status found?
  */
 private boolean updateTaskTrackerStatus(String trackerName, TaskTrackerStatus status) {
   TaskTrackerStatus oldStatus = (TaskTrackerStatus) taskTrackers.get(trackerName);
   if (oldStatus != null) {
     totalMaps -= oldStatus.countMapTasks();
     totalReduces -= oldStatus.countReduceTasks();
     if (status == null) {
       taskTrackers.remove(trackerName);
     }
   }
   if (status != null) {
     totalMaps += status.countMapTasks();
     totalReduces += status.countReduceTasks();
     taskTrackers.put(trackerName, status);
   }
   return oldStatus != null;
 }
Exemplo n.º 3
0
 public int compare(Object o1, Object o2) {
   TaskTrackerStatus p1 = (TaskTrackerStatus) o1;
   TaskTrackerStatus p2 = (TaskTrackerStatus) o2;
   if (p1.getLastSeen() < p2.getLastSeen()) {
     return -1;
   } else if (p1.getLastSeen() > p2.getLastSeen()) {
     return 1;
   } else {
     return (p1.getTrackerName().compareTo(p2.getTrackerName()));
   }
 }
Exemplo n.º 4
0
  /**
   * Accept and process a new TaskTracker profile. We might have known about the TaskTracker
   * previously, or it might be brand-new. All task-tracker structures have already been updated.
   * Just process the contained tasks and any jobs that might be affected.
   */
  void updateTaskStatuses(TaskTrackerStatus status) {
    for (Iterator it = status.taskReports(); it.hasNext(); ) {
      TaskStatus report = (TaskStatus) it.next();
      TaskInProgress tip = (TaskInProgress) taskidToTIPMap.get(report.getTaskId());
      if (tip == null) {
        LOG.info(
            "Serious problem.  While updating status, cannot find taskid " + report.getTaskId());
      } else {
        JobInProgress job = tip.getJob();
        job.updateTaskStatus(tip, report);

        if (report.getRunState() == TaskStatus.SUCCEEDED) {
          job.completedTask(tip, report.getTaskId());
        } else if (report.getRunState() == TaskStatus.FAILED) {
          // Tell the job to fail the relevant task
          job.failedTask(tip, report.getTaskId(), status.getTrackerName());
        }
      }
    }
  }
Exemplo n.º 5
0
  /**
   * A TaskTracker wants to know the physical locations of completed, but not yet closed, tasks.
   * This exists so the reduce task thread can locate map task outputs.
   */
  public synchronized MapOutputLocation[] locateMapOutputs(
      String taskId, String[][] mapTasksNeeded) {
    ArrayList v = new ArrayList();
    for (int i = 0; i < mapTasksNeeded.length; i++) {
      for (int j = 0; j < mapTasksNeeded[i].length; j++) {
        TaskInProgress tip = (TaskInProgress) taskidToTIPMap.get(mapTasksNeeded[i][j]);
        if (tip != null && tip.isComplete(mapTasksNeeded[i][j])) {
          String trackerId = (String) taskidToTrackerMap.get(mapTasksNeeded[i][j]);
          TaskTrackerStatus tracker;
          synchronized (taskTrackers) {
            tracker = (TaskTrackerStatus) taskTrackers.get(trackerId);
          }
          v.add(new MapOutputLocation(mapTasksNeeded[i][j], tracker.getHost(), tracker.getPort()));
          break;
        }
      }
    }
    // randomly shuffle results to load-balance map output requests
    Collections.shuffle(v);

    return (MapOutputLocation[]) v.toArray(new MapOutputLocation[v.size()]);
  }
Exemplo n.º 6
0
    /**
     * The run method lives for the life of the JobTracker, and removes TaskTrackers that have not
     * checked in for some time.
     */
    public void run() {
      while (shouldRun) {
        //
        // Thread runs periodically to check whether trackers should be expired.
        // The sleep interval must be no more than half the maximum expiry time
        // for a task tracker.
        //
        try {
          Thread.sleep(TASKTRACKER_EXPIRY_INTERVAL / 3);
        } catch (InterruptedException ie) {
        }

        //
        // Loop through all expired items in the queue
        //
        synchronized (taskTrackers) {
          synchronized (trackerExpiryQueue) {
            long now = System.currentTimeMillis();
            TaskTrackerStatus leastRecent = null;
            while ((trackerExpiryQueue.size() > 0)
                && ((leastRecent = (TaskTrackerStatus) trackerExpiryQueue.first()) != null)
                && (now - leastRecent.getLastSeen() > TASKTRACKER_EXPIRY_INTERVAL)) {

              // Remove profile from head of queue
              trackerExpiryQueue.remove(leastRecent);
              String trackerName = leastRecent.getTrackerName();

              // Figure out if last-seen time should be updated, or if tracker is dead
              TaskTrackerStatus newProfile =
                  (TaskTrackerStatus) taskTrackers.get(leastRecent.getTrackerName());
              // Items might leave the taskTracker set through other means; the
              // status stored in 'taskTrackers' might be null, which means the
              // tracker has already been destroyed.
              if (newProfile != null) {
                if (now - newProfile.getLastSeen() > TASKTRACKER_EXPIRY_INTERVAL) {
                  // Remove completely
                  updateTaskTrackerStatus(trackerName, null);
                  lostTaskTracker(leastRecent.getTrackerName());
                } else {
                  // Update time by inserting latest profile
                  trackerExpiryQueue.add(newProfile);
                }
              }
            }
          }
        }
      }
    }
Exemplo n.º 7
0
  /**
   * A tracker wants to know if there's a Task to run. Returns a task we'd like the TaskTracker to
   * execute right now.
   *
   * <p>Eventually this function should compute load on the various TaskTrackers, and incorporate
   * knowledge of DFS file placement. But for right now, it just grabs a single item out of the
   * pending task list and hands it back.
   */
  public synchronized Task pollForNewTask(String taskTracker) {
    //
    // Compute average map and reduce task numbers across pool
    //
    int avgMaps = 0;
    int avgReduces = 0;
    int numTaskTrackers;
    TaskTrackerStatus tts;
    synchronized (taskTrackers) {
      numTaskTrackers = taskTrackers.size();
      tts = (TaskTrackerStatus) taskTrackers.get(taskTracker);
    }
    if (numTaskTrackers > 0) {
      avgMaps = totalMaps / numTaskTrackers;
      avgReduces = totalReduces / numTaskTrackers;
    }
    int totalCapacity = numTaskTrackers * maxCurrentTasks;
    //
    // Get map + reduce counts for the current tracker.
    //
    if (tts == null) {
      LOG.warning("Unknown task tracker polling; ignoring: " + taskTracker);
      return null;
    }

    int numMaps = tts.countMapTasks();
    int numReduces = tts.countReduceTasks();

    //
    // In the below steps, we allocate first a map task (if appropriate),
    // and then a reduce task if appropriate.  We go through all jobs
    // in order of job arrival; jobs only get serviced if their
    // predecessors are serviced, too.
    //

    //
    // We hand a task to the current taskTracker if the given machine
    // has a workload that's equal to or less than the averageMaps
    // +/- TASK_ALLOC_EPSILON.  (That epsilon is in place in case
    // there is an odd machine that is failing for some reason but
    // has not yet been removed from the pool, making capacity seem
    // larger than it really is.)
    //
    synchronized (jobsByArrival) {
      if ((numMaps < maxCurrentTasks) && (numMaps <= (avgMaps + TASK_ALLOC_EPSILON))) {

        int totalNeededMaps = 0;
        for (Iterator it = jobsByArrival.iterator(); it.hasNext(); ) {
          JobInProgress job = (JobInProgress) it.next();
          if (job.getStatus().getRunState() != JobStatus.RUNNING) {
            continue;
          }

          Task t = job.obtainNewMapTask(taskTracker, tts);
          if (t != null) {
            return t;
          }

          //
          // Beyond the highest-priority task, reserve a little
          // room for failures and speculative executions; don't
          // schedule tasks to the hilt.
          //
          totalNeededMaps += job.desiredMaps();
          double padding = 0;
          if (totalCapacity > MIN_SLOTS_FOR_PADDING) {
            padding = Math.min(maxCurrentTasks, totalNeededMaps * PAD_FRACTION);
          }
          if (totalNeededMaps + padding >= totalCapacity) {
            break;
          }
        }
      }

      //
      // Same thing, but for reduce tasks
      //
      if ((numReduces < maxCurrentTasks) && (numReduces <= (avgReduces + TASK_ALLOC_EPSILON))) {

        int totalNeededReduces = 0;
        for (Iterator it = jobsByArrival.iterator(); it.hasNext(); ) {
          JobInProgress job = (JobInProgress) it.next();
          if (job.getStatus().getRunState() != JobStatus.RUNNING) {
            continue;
          }

          Task t = job.obtainNewReduceTask(taskTracker, tts);
          if (t != null) {
            return t;
          }

          //
          // Beyond the highest-priority task, reserve a little
          // room for failures and speculative executions; don't
          // schedule tasks to the hilt.
          //
          totalNeededReduces += job.desiredReduces();
          double padding = 0;
          if (totalCapacity > MIN_SLOTS_FOR_PADDING) {
            padding = Math.min(maxCurrentTasks, totalNeededReduces * PAD_FRACTION);
          }
          if (totalNeededReduces + padding >= totalCapacity) {
            break;
          }
        }
      }
    }
    return null;
  }