org.qbroker.common

Class ThreadPool

java.lang.Object

org.qbroker.common.ThreadPool

All Implemented Interfaces:

java.lang.Runnable

public class ThreadPool
extends java.lang.Object
implements java.lang.Runnable

ThreadPool is a container to maintain multiple threads of the same object. The number of active threads ranges from the minimum to its capacity. The application is able to checkout an active thread from the pool. As long as the active thread is checked out, the application is able to assign a task to the thread. The task will be picked up by the checked-out thread sooner or later. Once the thread picks up the task, it will invoke the given method with the task as the only argument. At this time, the thread stays busy until the method exits. The thread will be checked in to the pool. The application has control over the number of active threads by checking out or checking in.

Once a task is completed by a thread, the thread will automatically check itself in. The pool will decide the fate of the thread. If the thread is to be removed from the pool, the thread will stop and exit. Otherwise, it will be idle, waiting for the next checkout. If all the threads are active, ThreadPool will create a new thread as long as the pool is not full. ThreadPool will always try to maintain the minmum number of running threads. Therefore, in case there are more running threads than the minimum required number, any newly checked-in thread may get stopped to save resources.

ThreadPool supports any method, as long as it is MT-Safe. The argument of the method has to be an Array of Class. It will be used to locate the method on the object. Therefore, you have to specify the name of the method, its pTypes array and the object itself in order to create a ThreadPool.

Author:

yannanlu@yahoo.com

Field Summary

Fields

Modifier and Type	Field and Description
static int	POOL_CHECKOUT
static int	POOL_CLOSED
static int	POOL_INVALID
static int	POOL_OK

Constructor Summary

Constructors

Constructor and Description
ThreadPool(java.lang.String name, int minSize, int capacity, java.lang.Object obj, java.lang.String methodName, java.lang.Class[] pTypes)

Method Summary

Modifier and Type	Method and Description
int	assign(java.lang.Object[] task, int id) It assigns a task to the newly activated id-th thread.
int	checkin(java.lang.Thread thr) It checks in an unused thread and returns the status code for it.
protected int	checkin(java.lang.Thread thr, int s) It checks in a thread and returns it to the pool based on its status.
java.lang.Thread	checkout(long milliSec) It checks out an idle thread of the object and activates it.
void	close()
protected java.lang.Thread	create()
protected void	finalize()
int	getCapacity() returns capacity of the pool
int	getCount() returns number of outstanding tasks
int	getDepth() returns number of active instances not in use
int	getId(java.lang.Thread thr) return the ID of the object or -1 if it does not contain such object
java.lang.String	getName()
int	getSize() returns number of active instances regardless it is used or not
int	getStatus()
int	getStatus(int id)
void	run()

Methods inherited from class java.lang.Object

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

Field Detail

POOL_OK

public static final int POOL_OK

See Also:

Constant Field Values

POOL_CHECKOUT

public static final int POOL_CHECKOUT

See Also:

Constant Field Values

POOL_INVALID

public static final int POOL_INVALID

See Also:

Constant Field Values

POOL_CLOSED

public static final int POOL_CLOSED

See Also:

Constant Field Values

Constructor Detail

ThreadPool

public ThreadPool(java.lang.String name,
                  int minSize,
                  int capacity,
                  java.lang.Object obj,
                  java.lang.String methodName,
                  java.lang.Class[] pTypes)

Method Detail

checkout

public java.lang.Thread checkout(long milliSec)

It checks out an idle thread of the object and activates it. If there is no idle thread available and there is no room for any new thread, it simply returns null to indicate no thread available. If the pool is not full yet, it will try to create a new thread. If the creation is sucessful, it returns the thread. Otherwise, null is returned. Application is supposed to check the size if it gets null.

Due to MT features, you have to provide milliSec as the waitinmg time.

checkin

public int checkin(java.lang.Thread thr)

It checks in an unused thread and returns the status code for it. If it is recycled, POOL_OK will be returned. Otherwise, POLL_CLOSED is for removed, POOL_INVALID for recreated, and -1 for no such thread in the pool.

checkin

protected int checkin(java.lang.Thread thr,
                      int s)

It checks in a thread and returns it to the pool based on its status. The pool will decide if to recycle the thread or destroy it. If it is recycled, POOL_OK will be returned. Otherwise, POLL_CLOSED is for removed, POOL_INVALID for recreated, and -1 for no such thread in the pool.

assign

public int assign(java.lang.Object[] task,
                  int id)

It assigns a task to the newly activated id-th thread. A task is the argument array for the method. Up on success, it returns the number of outstanding tasks or -1 otherwise.

run

public void run()

Specified by:

run in interface java.lang.Runnable

getName

public java.lang.String getName()

getCapacity

public int getCapacity()

returns capacity of the pool

getSize

public int getSize()

returns number of active instances regardless it is used or not

getDepth

public int getDepth()

returns number of active instances not in use

getCount

public int getCount()

returns number of outstanding tasks

getStatus

public int getStatus(int id)

getStatus

public int getStatus()

getId

public int getId(java.lang.Thread thr)

return the ID of the object or -1 if it does not contain such object

close

public void close()

finalize

protected void finalize()

Overrides:

finalize in class java.lang.Object

create

protected java.lang.Thread create()
                           throws java.lang.RuntimeException

Throws:

java.lang.RuntimeException