Package weka.knowledgeflow

Class StepTask<T>

java.lang.Object

weka.knowledgeflow.StepTask<T>

Type Parameters:

T - the type of the result stored in the returned ExecutionResult object

All Implemented Interfaces:

java.io.Serializable, java.util.concurrent.Callable<ExecutionResult<T>>

public abstract class StepTask<T>
extends java.lang.Object
implements java.util.concurrent.Callable<ExecutionResult<T>>, java.io.Serializable

A task that can be executed by the ExecutionEnvironment's submitTask() service. Step's wanting to use this to execute units of work in parallel must extends it and can work with it in one of two ways:

1. By using the Future returned by submitTask(), or
2. By registering an implementation of StepCallback when creating a subclass of StepTask.
Subclasses of StepTask should store their results (and potentially errors) in the provided ExecutionResult member variable (obtainable by calling getExecutionResult()).

Author:

Mark Hall (mhall{[at]}pentaho{[dot]}com)

See Also:

Serialized Form

Constructor Summary

Constructors

Constructor	Description
StepTask(Step source)	Constructor.
StepTask(Step source, boolean resourceIntensive)	Constructor.
StepTask(Step source, StepTaskCallback<T> callback)	Constructor with supplied callback.
StepTask(Step source, StepTaskCallback<T> callback, boolean resourceIntensive)	Constructor with supplied callback.

Method Summary

Modifier and Type	Method	Description
ExecutionResult<T>	call()	Executor service calls this method to do the work
boolean	getMustRunSingleThreaded()	Get whether this StepTask must run single threaded - i.e.
boolean	isResourceIntensive()	Get whether this StepTask is resource intensive (cpu/memory) or not.
abstract void	process()	The actual work gets done here.
void	setMustRunSingleThreaded(boolean singleThreaded)	Set whether this StepTask must run single threaded - i.e.
void	setResourceIntensive(boolean resourceIntensive)	Set whether this StepTask is resource intensive (cpu/memory) or not.

Methods inherited from class java.lang.Object

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

Constructor Detail

StepTask

public StepTask(Step source)

Constructor. Use this constructor if you are going to access the Future returned by ExecutionEnvironment.submitTask().

Parameters:

source - the source step producing this task

StepTask

public StepTask(Step source,
                boolean resourceIntensive)

Constructor. Use this constructor if you are going to access the Future returned by ExecutionEnvironment.submitTask()

Parameters:

source - the source step producing this task

resourceIntensive - true if this task is cpu/memory intensive

StepTask

public StepTask(Step source,
                StepTaskCallback<T> callback)

Constructor with supplied callback. Use this constructor to be notified via the supplied callback when a the task has completed processing

Parameters:

source - the source step producing this task

callback - the callback to use

StepTask

public StepTask(Step source,
                StepTaskCallback<T> callback,
                boolean resourceIntensive)

Constructor with supplied callback. Use this constructor to be notified via the supplied callback when a task has completed processing

Parameters:

source - the source step producing this task

callback - the callback to use

resourceIntensive - true if this task is cpu/memory intensive

Method Detail

setResourceIntensive

public void setResourceIntensive(boolean resourceIntensive)

Set whether this StepTask is resource intensive (cpu/memory) or not. By default, a StepTask is resource intensive

Parameters:

resourceIntensive - false if this StepTask is not resource intensive

isResourceIntensive

public boolean isResourceIntensive()

Get whether this StepTask is resource intensive (cpu/memory) or not. By default, a StepTask is resource intensive

Returns:

false if this StepTask is not resource intensive

setMustRunSingleThreaded

public void setMustRunSingleThreaded(boolean singleThreaded)

Set whether this StepTask must run single threaded - i.e. only one of these tasks is executing at any one time in the JVM. The Knowledge Flow uses a special executor service with a single worker thread to execute these tasks. This property, if true, overrides isResourceIntensive().

Parameters:

singleThreaded - true if this task must run single threaded

getMustRunSingleThreaded

public boolean getMustRunSingleThreaded()

Get whether this StepTask must run single threaded - i.e. only one of these tasks is executing at any one time in the JVM. The Knowledge Flow uses a special executor service with a single worker thread to execute these tasks. This property, if true, overrides isResourceIntensive().

Returns:

true if this task must run single threaded

call

public ExecutionResult<T> call()
                        throws java.lang.Exception

Executor service calls this method to do the work

Specified by:

call in interface java.util.concurrent.Callable<T>

Returns:

the results of execution in an ExecutionResult

Throws:

java.lang.Exception

process

public abstract void process()
                      throws java.lang.Exception

The actual work gets done here. Subclasses to override. Subclasses can use getExecutionResult() to obtain an ExecutionResult object to store their results in

Throws:

java.lang.Exception