Package org.apache.flink.runtime.operators

Class ReduceDriver<T>

java.lang.Object

org.apache.flink.runtime.operators.ReduceDriver<T>

All Implemented Interfaces:

Driver<ReduceFunction<T>,T>

public class ReduceDriver<T>
extends Object
implements Driver<ReduceFunction<T>,T>

Reduce driver which is executed by a Task Manager. The task has a single input and one or multiple outputs. It is provided with a ReduceFunction implementation.

The ReduceDriver creates an iterator over all records from its input. The iterator returns all records grouped by their key. The elements are handed pairwise to the reduce() method of the ReduceFunction.

See Also:

ReduceFunction

Constructor Summary

Constructors

Constructor	Description
ReduceDriver()

Method Summary

Modifier and Type	Method	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<ReduceFunction<T>>	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<ReduceFunction<T>,T> context)

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

ReduceDriver

public ReduceDriver()

Method Detail

setup

public void setup(TaskContext<ReduceFunction<T>,T> context)

Specified by:

setup in interface Driver<ReduceFunction<T>,T>

getNumberOfInputs

public int getNumberOfInputs()

Description copied from interface: Driver

Gets the number of inputs that the task has.

Specified by:

getNumberOfInputs in interface Driver<ReduceFunction<T>,T>

Returns:

The number of inputs.

getStubType

public Class<ReduceFunction<T>> getStubType()

Description copied from interface: Driver

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

Specified by:

getStubType in interface Driver<ReduceFunction<T>,T>

Returns:

The class of the stub type run by the task.

getNumberOfDriverComparators

public int getNumberOfDriverComparators()

Description copied from interface: Driver

Gets the number of comparators required for this driver.

Specified by:

getNumberOfDriverComparators in interface Driver<ReduceFunction<T>,T>

Returns:

The number of comparators required for this driver.

prepare

public void prepare()
             throws Exception

Description copied from interface: Driver

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

Specified by:

prepare in interface Driver<ReduceFunction<T>,T>

Throws:

Exception - Exceptions may be forwarded and signal task failure.

run

public void run()
         throws Exception

Description copied from interface: Driver

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

Specified by:

run in interface Driver<ReduceFunction<T>,T>

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

public void cleanup()

Description copied from interface: Driver

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

Specified by:

cleanup in interface Driver<ReduceFunction<T>,T>

cancel

public void cancel()

Description copied from interface: Driver

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

Specified by:

cancel in interface Driver<ReduceFunction<T>,T>