/** * 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()]); }