ariba.util.core
Class ThreadPool

java.lang.Object
  ariba.util.core.ThreadPool

All Implemented Interfaces:

Executor

public class ThreadPool
extends java.lang.Object
implements Executor

Standard non-extensible thread pool implememtation on top of queue. Users provide Runnable implementations and call execute.

The pool is constituted of Threads retrieve from a ThreadFactory. Normally, the number of threads created cannot exceed a specified number of threads, and new threads are created if necessary until the limit is reached.

Each thread pool is configured with a RejectedExecutionHandler. When the user call execute, the runnable is added to a queue and a thread is notified. If all threads are busy, then one will be added until the thread size limit is reached. When this happens, outstanding runnables are queued up. When the queue reaches its (configurable) capacity, the RejectedExecutionHandler will be called upon to handle the situation.

At present there are 2 handlers:

• DefaultRejectedExecutionHandler simply drops the runnable and throws a RejectedExecutionException.
• ThreadPoolRejectedExecutionHandler will increaese the queue size by roughly 10% to accommodate the new runnables while simultaneously add more threads regardless of the number of threads already created to reduce the queue size.

Pooled threads remaining idle for longer than the specified time out, will be terminated. A timeout of 0 will result in no idle threads being terminated.

Based on the above discussion, we can arrive at the following guidelines:

• if response time is important, it is better to have a shorter queue size and more threads, and use ThreadPoolRejectedExecutionHandler as the handler.
• if memory (or CPU) resource is important (so runnables can wait), it is better to have a larger queue and less threads, and a handler that does not add threads indefinitely.

Constructor Summary

ThreadPool(java.lang.String name, ThreadManager threadManager)
Creates a new ThreadPool starting 1 thread and containing up to 5 threads.

ThreadPool(java.lang.String name, ThreadManager threadManager, int minThreads, int maxThreads, long timeout, int queueCapacity, java.lang.String handlerClassName)
Creates a new ThreadPool.

Method Summary

void	execute(java.lang.Runnable command) Retrieves a thread from the pool and have it execute the given runnable.
int	getMaxThreadCount() Returns the configured max thread limit.
ThreadPoolMonitor	getMonitor()
int	getQueueSize() Returns the number of objects waiting in the queue
int	getThreadCount() Returns the size of the ThreadPool
void	setMonitor(ThreadPoolMonitor monitor) not synchronized, last one wins

Methods inherited from class java.lang.Object

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

Constructor Detail

ThreadPool

public ThreadPool(java.lang.String name,
                  ThreadManager threadManager)

Creates a new ThreadPool starting 1 thread and containing up to 5 threads. Threads die after 30 minutes of inactivity.

Parameters:

name - the name used for the threads

threadManager - the ThreadManager used to manage the threads

ThreadPool

public ThreadPool(java.lang.String name,
                  ThreadManager threadManager,
                  int minThreads,
                  int maxThreads,
                  long timeout,
                  int queueCapacity,
                  java.lang.String handlerClassName)

Creates a new ThreadPool.

Parameters:

name - the name used for the threads

threadManager - the ThreadManager used to manage the threads

minThreads - the number of threads to start with

maxThreads - the maximum number of threads managed by the pool

timeout - the maximum time a thread remains inactive

queueCapacity - the size of the queue to hold the runnables. Note that it is possible for the queue to grow beyond this initial capacity.

handlerClassName - the name of the handling class. If null DefaultRejectedExecutionHandler will be used.

Method Detail

execute

public void execute(java.lang.Runnable command)

Retrieves a thread from the pool and have it execute the given runnable.

Specified by:

execute in interface Executor

Parameters:

command - the task to be executed

Throws:

RejectedExecutionException - if the execution is rejected.

setMonitor

public void setMonitor(ThreadPoolMonitor monitor)

not synchronized, last one wins

getMonitor

public ThreadPoolMonitor getMonitor()

getThreadCount

public int getThreadCount()

Returns the size of the ThreadPool

getQueueSize

public int getQueueSize()

Returns the number of objects waiting in the queue

getMaxThreadCount

public int getMaxThreadCount()

Returns the configured max thread limit.

Returns: