org.apache.nutch.mapReduce
Interface InterTrackerProtocol

All Known Implementing Classes:

JobTracker

public interface InterTrackerProtocol

Protocol that a TaskTracker and the central JobTracker use to communicate. The JobTracker is the Server, which implements this protocol.

Field Summary

static int	TRACKERS_OK
static int	UNKNOWN_TASKTRACKER

Method Summary

IntWritable	emitHeartbeat(TaskTrackerStatus status, BooleanWritable initialContact) Called regularly by the task tracker to update the status of its tasks within the job tracker.
String	getFilesystemName() The task tracker calls this once, to discern where it can find files referred to by the JobTracker
MapOutputLocation[]	locateMapOutputs(String taskId, String[] mapTasksNeeded) Called by a reduce task to find which map tasks are completed.
String	pollForClosedTask(String trackerName) Called to find which tasks that have been run by this tracker are now closed, i.e., their job is complete.
Task	pollForNewTask(String trackerName) Called to get new tasks from from the job tracker for this tracker.

Field Detail

TRACKERS_OK

public static final int TRACKERS_OK

See Also:

Constant Field Values

UNKNOWN_TASKTRACKER

public static final int UNKNOWN_TASKTRACKER

See Also:

Constant Field Values

Method Detail

emitHeartbeat

public IntWritable emitHeartbeat(TaskTrackerStatus status,
                                 BooleanWritable initialContact)

Called regularly by the task tracker to update the status of its tasks within the job tracker. JobTracker responds with a code that tells the TaskTracker whether all is well. TaskTracker must also indicate whether this is the first interaction (since state refresh)

pollForNewTask

public Task pollForNewTask(String trackerName)

Called to get new tasks from from the job tracker for this tracker.

pollForClosedTask

public String pollForClosedTask(String trackerName)

Called to find which tasks that have been run by this tracker are now closed, i.e., their job is complete. This is used to, e.g., notify a map task that its output is no longer needed and may be removed.

locateMapOutputs

public MapOutputLocation[] locateMapOutputs(String taskId,
                                            String[] mapTasksNeeded)

Called by a reduce task to find which map tasks are completed.

Parameters:

taskId - the reduce task id

mapTasksNeeded - an array of UTF8 naming map task ids whose output is needed.

Returns:

an array of MapOutputLocation

getFilesystemName

public String getFilesystemName()
                         throws IOException

The task tracker calls this once, to discern where it can find files referred to by the JobTracker

Throws:

IOException