ai.grakn.engine.tasks

Interface BackgroundTask

All Known Implementing Classes:

EndlessExecutionMockTask, FailingMockTask, LoaderTask, LongExecutionMockTask, MockBackgroundTask, PostProcessingTask, ResourceDeduplicationTask, ShortExecutionMockTask, UpdatingInstanceCountTask

public interface BackgroundTask

Interface which all tasks that wish to be scheduled for later execution as background tasks must implement.

Author:

Denis Lobanov

Method Summary

Modifier and Type	Method and Description
void	pause() Called to suspend the execution of a currently running task.
boolean	resume(java.util.function.Consumer<TaskCheckpoint> saveCheckpoint, TaskCheckpoint lastCheckpoint) This method may be called when resuming from a paused state or recovering from a crash or failure of any kind.
boolean	start(java.util.function.Consumer<TaskCheckpoint> saveCheckpoint, mjson.Json configuration) Called to start execution of the task, may be called on a newly scheduled or previously stopped task.
boolean	stop() Called to stop execution of the task, may be called on a running or paused task.

Method Detail

start

boolean start(java.util.function.Consumer<TaskCheckpoint> saveCheckpoint,
              mjson.Json configuration)

Called to start execution of the task, may be called on a newly scheduled or previously stopped task.

Parameters:

saveCheckpoint - Consumer which can be called at any time to save a state checkpoint that would allow the task to resume from this point should it crash.

Returns:

true if the task successfully completed, or false if it was stopped.

stop

boolean stop()

Called to stop execution of the task, may be called on a running or paused task. Task should stop gracefully.

Returns:

true if the task was successfully stopped, or false if it could not be stopped. TODO: Should we allow start() to be called after stop()?

pause

void pause()

Called to suspend the execution of a currently running task. The object may be destroyed after this call. TODO: stop running

resume

boolean resume(java.util.function.Consumer<TaskCheckpoint> saveCheckpoint,
               TaskCheckpoint lastCheckpoint)

This method may be called when resuming from a paused state or recovering from a crash or failure of any kind.

Parameters:

saveCheckpoint - Consumer which can be called at any time to save a state checkpoint that would allow the task to resume from this point should it crash.

lastCheckpoint - The last checkpoint as sent to saveCheckpoint.