com.google.appengine.tools.mapreduce.impl.shardedjob

Interface IncrementalTask

All Superinterfaces:

Serializable

All Known Subinterfaces:

IncrementalTaskWithContext

All Known Implementing Classes:

MapOnlyShardTask, MapShardTask, MergeShardTask, ReduceShardTask, SortShardTask, WorkerShardTask

public interface IncrementalTask
extends Serializable

Portion of a sharded job that will be run in a single task queue task.

Author:

ohler@google.com (Christian Ohler)

Method Summary

Methods

Modifier and Type	Method and Description
boolean	allowSliceRetry(boolean abandon)
void	cleanup() Clean up and release any resources claimed in prepare.
boolean	isDone()
void	jobCompleted(Status status) A job completed callback to allow resource cleanup and compaction of the finalized state.
void	prepare() Called immediately before run.
void	run() Runs this task.

Method Detail

prepare

void prepare()

Called immediately before run. This method should be very limited in scope and should not block, perform IO or fail for any reason other than Rejecting the request.

Throws:

RejectRequestException - when run cannot be called at this time.

run

void run()

Runs this task. This will be invoked over and over until isDone returns true. If this throws an exception, it may be retried a limited number of times according to a retry policy specified in ShardedJobSettings

Throws:

ShardFailureException - when shard should be retried

RuntimeException - when a slice should be retried

cleanup

void cleanup()

Clean up and release any resources claimed in prepare. Implementations of this method should not throw under any circumstances.

isDone

boolean isDone()

Returns:

true iff this task is done and run should no longer be invoked.

allowSliceRetry

boolean allowSliceRetry(boolean abandon)

Parameters:

abandon - true if a retry is due to an abandoned lock.

Returns:

true if a slice retry after failure are permitted.

jobCompleted

void jobCompleted(Status status)

A job completed callback to allow resource cleanup and compaction of the finalized state.

Parameters:

status - the status of the job