org.apache.flink.runtime.jobgraph.tasks

Interface TaskInvokable

All Known Implementing Classes:

AbstractInvokable, AbstractIterativeTask, AbstractTwoInputStreamTask, BatchTask, DataSinkTask, DataSourceTask, IterationHeadTask, IterationIntermediateTask, IterationSynchronizationSinkTask, IterationTailTask, MultipleInputStreamTask, OneInputStreamTask, SourceOperatorStreamTask, SourceStreamTask, StreamIterationHead, StreamIterationTail, StreamTask, TwoInputStreamTask

@Internal
public interface TaskInvokable

An invokable part of the task.

The TaskManager first calls the restore() method when executing a task. If the call succeeds and the task isn't cancelled then TM proceeds to invoke(). All operations of the task happen in these two methods (setting up input output stream readers and writers as well as the task's core operation).

After that, cleanUp(Throwable) is called (regardless of an failures or cancellations during the above calls).

Implementations must have a constructor with a single argument of type Environment.

Developer note: While constructors cannot be enforced at compile time, we did not yet venture on the endeavor of introducing factories (it is only an internal API after all, and with Java 8, one can use Class::new almost like a factory lambda.

See Also:

CheckpointableTask, CoordinatedTask, AbstractInvokable

Method Summary

Modifier and Type	Method and Description
void	cancel() This method is called when a task is canceled either as a result of a user abort or an execution failure.
void	cleanUp(Throwable throwable) Cleanup any resources used in invoke() OR restore().
void	invoke() Starts the execution.
boolean	isUsingNonBlockingInput()
void	maybeInterruptOnCancel(Thread toInterrupt, String taskName, Long timeout) Checks whether the task should be interrupted during cancellation and if so, execute the specified Runnable interruptAction.
void	restore() This method can be called before invoke() to restore an invokable object for the last valid state, if it has it.

Method Detail

invoke

void invoke()
     throws Exception

Starts the execution.

This method is called by the task manager when the actual execution of the task starts.

All resources should be cleaned up by calling cleanUp(Throwable) after the method returns.

Throws:

Exception

restore

void restore()
      throws Exception

This method can be called before invoke() to restore an invokable object for the last valid state, if it has it.

If invoke() is not called after this method for some reason (e.g. task cancellation); then all resources should be cleaned up by calling cleanUp(Throwable) ()} after the method returns.

Throws:

Exception

cleanUp

void cleanUp(@Nullable
             Throwable throwable)
      throws Exception

Cleanup any resources used in invoke() OR restore(). This method must be called regardless whether the aforementioned calls succeeded or failed.

Parameters:

throwable - iff failure happened during the execution of restore() or invoke(), null otherwise.

ATTENTION: CancelTaskException should not be treated as a failure.

Throws:

Exception

cancel

void cancel()
     throws Exception

This method is called when a task is canceled either as a result of a user abort or an execution failure. It can be overwritten to respond to shut down the user code properly.

Throws:

Exception

isUsingNonBlockingInput

boolean isUsingNonBlockingInput()

Returns:

true if blocking input such as InputGate.getNext() is used (as opposed to InputGate.pollNext(). To be removed together with the DataSet API.

maybeInterruptOnCancel

void maybeInterruptOnCancel(Thread toInterrupt,
                            @Nullable
                            String taskName,
                            @Nullable
                            Long timeout)

Checks whether the task should be interrupted during cancellation and if so, execute the specified Runnable interruptAction.

Parameters:

toInterrupt -

taskName - optional taskName to log stack trace

timeout - optional timeout to log stack trace