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()));
}
}
/**
* 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);
}
}
}
}
}
}
}