org.lsst.ccs.utilities.dispatch

Class ParallelCommandDispatcher<T>

java.lang.Object

org.lsst.ccs.utilities.dispatch.ParallelCommandDispatcher<T>

Type Parameters:

T - the nature of the code able to handle the CommandFor<T> Objects

public class ParallelCommandDispatcher<T>
extends Object

Dispatches a Command object to registered "executants" able to handle the command; each command execution may be handled by a different Thread so every registered agent does not have to wait for termination of code from the previous call.

BEWARE :

• The default constructor implementation uses a "cached" Thread Pool :
  • It is not guaranteed that events will be really executed in parallel. A fixed Thread pool knowing about the number of processors or a pure sequential code may be more efficient: test! (and ask for changes!)
    Better use this class if the Command's code takes quite a lot of time to execute.
  • The Thread pool may "choke" if commands to be executed are registered at a higher rate than they can be executed.
• The Threads handling the commands are deamon Threads. This may be a problem if you need an application Thread ... Moreover it is not guaranteed that all commands will be executed if the JVM abruptly terminates.
  This can be changed .... just ask!

Author:

bernard AMADE

Field Summary

Fields

Modifier and Type	Field and Description
protected CopyOnWriteArrayList<T>	list List of all registered agent that may take action.
protected ExecutorService	loop ExecutorService that deals with the Threads handling the commands.

Constructor Summary

Constructors

Constructor and Description
ParallelCommandDispatcher() Creates an asynchronous Dispatcher for Commands.
ParallelCommandDispatcher(boolean singleThread)
ParallelCommandDispatcher(ExecutorService execService) Creates an asynchronous Dispatcher for Commands: uses a specific ExecutorService.

Method Summary

Modifier and Type	Method and Description
void	addExecutant(T executant) adds an executant to the list of those going to execute Commands when needed.
void	dispatchCommand(CommandFor<T> command) Send a Command request for all registered executants.
void	removeExecutant(T executant) removes an executant form the list

Methods inherited from class java.lang.Object

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

Field Detail

loop

protected ExecutorService loop

ExecutorService that deals with the Threads handling the commands.

list

protected CopyOnWriteArrayList<T> list

List of all registered agent that may take action.

Constructor Detail

ParallelCommandDispatcher

public ParallelCommandDispatcher()

Creates an asynchronous Dispatcher for Commands. Uses the standard common ExecutorService for this package.

ParallelCommandDispatcher

public ParallelCommandDispatcher(ExecutorService execService)

Creates an asynchronous Dispatcher for Commands: uses a specific ExecutorService.

ParallelCommandDispatcher

public ParallelCommandDispatcher(boolean singleThread)

Method Detail

addExecutant

public void addExecutant(T executant)

adds an executant to the list of those going to execute Commands when needed.

Parameters:

executant -

removeExecutant

public void removeExecutant(T executant)

removes an executant form the list

Parameters:

executant -

dispatchCommand

public void dispatchCommand(CommandFor<T> command)

Send a Command request for all registered executants.

Parameters:

command -