org.apache.flink.runtime.operators

Interface Driver<S extends Function,OT>

Type Parameters:

S - The type of stub driven by this driver.

OT - The data type of the records produced by this driver.

All Known Subinterfaces:

ResettableDriver<S,OT>

All Known Implementing Classes:

AbstractCachedBuildSideJoinDriver, AbstractOuterJoinDriver, AllGroupCombineDriver, AllGroupReduceDriver, AllReduceDriver, BuildFirstCachedJoinDriver, BuildSecondCachedJoinDriver, CoGroupDriver, CoGroupRawDriver, CoGroupWithSolutionSetFirstDriver, CoGroupWithSolutionSetSecondDriver, CrossDriver, FlatMapDriver, FullOuterJoinDriver, GroupReduceCombineDriver, GroupReduceDriver, JoinDriver, JoinWithSolutionSetFirstDriver, JoinWithSolutionSetSecondDriver, LeftOuterJoinDriver, MapDriver, MapPartitionDriver, NoOpDriver, ReduceCombineDriver, ReduceDriver, RightOuterJoinDriver, UnionWithTempOperator

public interface Driver<S extends Function,OT>

The interface to be implemented by all drivers that run alone (or as the primary driver) in a task. A driver implements the actual code to perform a batch operation, like map(), reduce(), join(), or coGroup().

See Also:

TaskContext

Method Summary

Modifier and Type	Method and Description
void	cancel() This method is invoked when the driver must aborted in mid processing.
void	cleanup() This method is invoked in any case (clean termination and exception) at the end of the tasks operation.
int	getNumberOfDriverComparators() Gets the number of comparators required for this driver.
int	getNumberOfInputs() Gets the number of inputs that the task has.
Class<S>	getStubType() Gets the class of the stub type that is run by this task.
void	prepare() This method is called before the user code is opened.
void	run() The main operation method of the task.
void	setup(TaskContext<S,OT> context)

Method Detail

setup

void setup(TaskContext<S,OT> context)

getNumberOfInputs

int getNumberOfInputs()

Gets the number of inputs that the task has.

Returns:

The number of inputs.

getNumberOfDriverComparators

int getNumberOfDriverComparators()

Gets the number of comparators required for this driver.

Returns:

The number of comparators required for this driver.

getStubType

Class<S> getStubType()

Gets the class of the stub type that is run by this task. For example, a MapTask should return MapFunction.class.

Returns:

The class of the stub type run by the task.

prepare

void prepare()
      throws Exception

This method is called before the user code is opened. An exception thrown by this method signals failure of the task.

Throws:

Exception - Exceptions may be forwarded and signal task failure.

run

void run()
  throws Exception

The main operation method of the task. It should call the user code with the data subsets until the input is depleted.

Throws:

Exception - Any exception thrown by this method signals task failure. Because exceptions in the user code typically signal situations where this instance in unable to proceed, exceptions from the user code should be forwarded.

cleanup

void cleanup()
      throws Exception

This method is invoked in any case (clean termination and exception) at the end of the tasks operation.

Throws:

Exception - Exceptions may be forwarded.

cancel

void cancel()
     throws Exception

This method is invoked when the driver must aborted in mid processing. It is invoked asynchronously by a different thread.

Throws:

Exception - Exceptions may be forwarded.