org.xlattice.util.threads
Class ThreadPool

java.lang.Object
  org.xlattice.util.threads.ThreadPool

public class ThreadPool
extends java.lang.Object

Fixed size pool of Killable threads which consume a (possibly variable in size) queue of Killable jobs, Runnables with a die() method. XXX Modify to allow change in pool capacity.

Author:

Jim Dixon

Field Summary

protected boolean	daemon
protected JobQueue	jobQ we synchronize access to this
protected int	maxLenJobQ If -1, length varies dynamically with no specific max; otherwise, rejects jobs if max queue length exceeded.
protected int	maxThreads
protected java.lang.String	name
protected java.lang.ThreadGroup	threadGroup
protected ThreadList	workers we synchronize access to this

Constructor Summary

ThreadPool(java.lang.String s, int maxP)
Create a thread pool with a default queue size of 128 and using a default ThreadGroup

ThreadPool(java.lang.String s, int maxP, int maxJ, java.lang.ThreadGroup tg, boolean b)
Create a thread pool, making up a default name if necessary.

ThreadPool(java.lang.String s, int maxP, java.lang.ThreadGroup tg)
Create a thread group with a default queue size of 128

Method Summary

boolean	accept(java.lang.Runnable job) Accept a Runnable into the job queue.
int	getMaxLenJobQueue()
int	getMaxThreads()
java.lang.String	getName()
int	size()
void	stop() XXX Doesn't actually wait for worker threads to stop running.

Methods inherited from class java.lang.Object

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

Field Detail

name

protected final java.lang.String name

threadGroup

protected final java.lang.ThreadGroup threadGroup

maxThreads

protected final int maxThreads

workers

protected final ThreadList workers

we synchronize access to this

maxLenJobQ

protected final int maxLenJobQ

If -1, length varies dynamically with no specific max; otherwise, rejects jobs if max queue length exceeded.

jobQ

protected final JobQueue jobQ

we synchronize access to this

daemon

protected final boolean daemon

Constructor Detail

ThreadPool

public ThreadPool(java.lang.String s,
                  int maxP)

Create a thread pool with a default queue size of 128 and using a default ThreadGroup

ThreadPool

public ThreadPool(java.lang.String s,
                  int maxP,
                  java.lang.ThreadGroup tg)

Create a thread group with a default queue size of 128

ThreadPool

public ThreadPool(java.lang.String s,
                  int maxP,
                  int maxJ,
                  java.lang.ThreadGroup tg,
                  boolean b)

Create a thread pool, making up a default name if necessary. XXX Probably should force a minimum maxP and maxJ

Parameters:

s - name of thread pool, base for thread names

maxP - maximum number of idle threads in pool

maxJ - maximum number of jobs in the queue

tg - thread group threads will belong to

Method Detail

getName

public java.lang.String getName()

Returns:

base name of this thread group

getMaxLenJobQueue

public int getMaxLenJobQueue()

Returns:

maximum number of jobs allowed in the queue

getMaxThreads

public int getMaxThreads()

Returns:

maximum number of threads in the pool

size

public int size()

Returns:

number of threads in the pool

accept

public boolean accept(java.lang.Runnable job)

Accept a Runnable into the job queue. If there are no idle workers, then if possible a new worker is created. The job is then queued, if there is enough room in the queue. There is no guarantee that the job causing a new worker to be created will be run in that new thread or even added to the queue.

Returns:

whether the job could be queued

stop

public void stop()

XXX Doesn't actually wait for worker threads to stop running. Preferred behavior: take a snapshot of all workers, tell each one to die, and then wait until isAlive() is false for each thread. Could use join() instead. Better: build a multi-level kill() that first checks isAlive(), then sets the dying flag using die() and waits a short time, and finally actually