org.vibur.objectpool

Class ConcurrentLinkedPool<T>

java.lang.Object

org.vibur.objectpool.AbstractBasePoolService

org.vibur.objectpool.ConcurrentLinkedPool<T>

Type Parameters:

T - the type of objects held in this object pool

All Implemented Interfaces:

BasePoolService, NonValidatingPoolService<T>

public class ConcurrentLinkedPool<T>
extends AbstractBasePoolService
implements NonValidatingPoolService<T>

An implementation of a non-validating object pool based on a ConcurrentLinkedQueue and a Semaphore. This object pool does not implement any validation of whether the currently restored object has been taken before that from the object pool, or whether this object is currently in taken state.

This object pool provides support for fairness with regards to the waiting taker's threads. The creation of new objects and their lifecycle are controlled by a supplied during the object pool's creation time PoolObjectFactory.

This object pool has support for shrinking (reduction) of the number of allocated on the pool objects. Note that the shrinking may reduce the createdTotal() to less than the pool initialSize().

Author:

Simeon Malchev

See Also:

ConcurrentHolderLinkedPool

Constructor Summary

Constructors

Constructor and Description
ConcurrentLinkedPool(PoolObjectFactory<T> poolObjectFactory, int initialSize, int maxSize, boolean fair) Creates a new ConcurrentLinkedPool with the given PoolObjectFactory, initial and max sizes, fairness setting.

Method Summary

Methods

Modifier and Type	Method and Description
int	createdTotal() Returns the total number of created objects which currently exist for this object pool.
int	initialSize() Returns the initialSize of this object pool at construction time.
boolean	isFair() Returns the fairness setting of this object pool.
boolean	isTerminated() Returns the current terminated state of this object pool.
int	maxSize() Returns the maxSize of this object pool.
protected T	newObject()
int	reduceCreated(int reduction, boolean ignoreInitialSize) Tries to remove (and destroy) up to reduction objects from the object pool.
int	remainingCapacity() Returns the remaining capacity of this object pool, i.e.
void	restore(T object) Restores (returns) an object to the object pool.
void	restore(T object, boolean valid) Restores (returns) an object to the object pool.
T	take() Takes an object from the object pool if there is such available.
T	takeUninterruptibly() Takes an object from the object pool if there is such available.
void	terminate() Terminates this object pool.
T	tryTake() Tries to take an object from the object pool if there is one which is immediately available.
T	tryTake(long timeout, TimeUnit unit) Takes an object from the object pool if there is such available.

Methods inherited from class org.vibur.objectpool.AbstractBasePoolService

drainCreated, remainingCreated, taken, toString

Methods inherited from class java.lang.Object

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

Methods inherited from interface org.vibur.objectpool.BasePoolService

drainCreated, remainingCreated, taken

Constructor Detail

ConcurrentLinkedPool

public ConcurrentLinkedPool(PoolObjectFactory<T> poolObjectFactory,
                    int initialSize,
                    int maxSize,
                    boolean fair)

Creates a new ConcurrentLinkedPool with the given PoolObjectFactory, initial and max sizes, fairness setting.

Parameters:

poolObjectFactory - the factory which will be used to create new objects in this object pool as well as to control their lifecycle

initialSize - the object pool initial size, i.e. the initial number of allocated in the object pool objects

maxSize - the object pool max size, i.e. the max number of allocated in the object pool objects

fair - the object pool's fairness setting with regards to waiting threads

Throws:

IllegalArgumentException - if one of the following holds:
initialSize < 0 || maxSize < 1 || maxSize < initialSize

NullPointerException - if poolObjectFactory is null

Method Detail

take

public T take()

Takes an object from the object pool if there is such available. This is a blocking call which waits indefinitely until an object becomes available. If the calling thread is interrupted while waiting this call will return null and the thread's interrupted status will be set to true.

Specified by:

take in interface NonValidatingPoolService<T>

Returns:

an object taken from the object pool or null if was interrupted while waiting

takeUninterruptibly

public T takeUninterruptibly()

Takes an object from the object pool if there is such available. This is a blocking call which waits indefinitely until an object becomes available.

Specified by:

takeUninterruptibly in interface NonValidatingPoolService<T>

Returns:

an object taken from the object pool

tryTake

public T tryTake(long timeout,
        TimeUnit unit)

Takes an object from the object pool if there is such available. This is a blocking call which waits up to the specified timeout for an object to become available. If the calling thread is interrupted while waiting this call will return null and the thread's interrupted status will be set to true.

Specified by:

tryTake in interface NonValidatingPoolService<T>

Parameters:

timeout - the maximum time to wait for an object to become available in the object pool

unit - the time unit of the timeout argument

Returns:

an object taken from the object pool or null if the specified timeout expires or if it was interrupted while waiting

tryTake

public T tryTake()

Tries to take an object from the object pool if there is one which is immediately available. Returns null if no object is available at the moment of the call.

Specified by:

tryTake in interface NonValidatingPoolService<T>

Returns:

an object from the object pool or null if there is no object available in the object pool

newObject

protected T newObject()

restore

public void restore(T object)

Restores (returns) an object to the object pool. The object pool will not do any validation whether the object restored has been taken before from this object pool or whether it is currently in taken state. Equivalent to calling restore(Object, true).

Specified by:

restore in interface NonValidatingPoolService<T>

Parameters:

object - an object to be restored (returned) to this object pool

restore

public void restore(T object,
           boolean valid)

Restores (returns) an object to the object pool. The object pool will not do any validation whether the object restored has been taken before from this object pool or whether it is currently in taken state.

Specified by:

restore in interface NonValidatingPoolService<T>

Parameters:

object - an object to be restored (returned) to this object pool

valid - if true the restored object is presumed to be in valid (healthy) state, otherwise it is treated as invalid

createdTotal

public int createdTotal()

Returns the total number of created objects which currently exist for this object pool. This number is equal to BasePoolService.taken() + BasePoolService.remainingCreated(). Typically used for testing an debugging purposes.

Specified by:

createdTotal in interface BasePoolService

Returns:

the total number of created objects for this object pool

remainingCapacity

public int remainingCapacity()

Returns the remaining capacity of this object pool, i.e. the number of objects which could be taken from this object pool without blocking. It is not guaranteed that all these objects exist at the time of the call (i.e. are already created) in the object pool - some of them might be created on demand upon take requests. Also see BasePoolService.remainingCreated(). Typically used for testing an debugging purposes.

Specified by:

remainingCapacity in interface BasePoolService

Returns:

the object pool's remaining capacity

initialSize

public int initialSize()

Returns the initialSize of this object pool at construction time. This parameter never changes.

Specified by:

initialSize in interface BasePoolService

Returns:

the object pool's initialSize

maxSize

public int maxSize()

Returns the maxSize of this object pool. This parameter never changes.

Specified by:

maxSize in interface BasePoolService

Returns:

the object pool's maxSize

reduceCreated

public int reduceCreated(int reduction,
                boolean ignoreInitialSize)

Tries to remove (and destroy) up to reduction objects from the object pool. May bring the object pool's BasePoolService.createdTotal() to less then its BasePoolService.initialSize().

Specified by:

reduceCreated in interface BasePoolService

Parameters:

reduction - the desired amount of objects to be removed

ignoreInitialSize - specifies whether the BasePoolService.createdTotal() may be reduced to less than BasePoolService.initialSize()

Returns:

the actual amount of objects removed

terminate

public void terminate()

Terminates this object pool. Once terminated the object pool cannot be more revived. All take and restore operations called on a terminated object pool should throw an exception or be ignored. Invocation has no additional effect if already terminated.

Specified by:

terminate in interface BasePoolService

isTerminated

public boolean isTerminated()

Returns the current terminated state of this object pool.

Specified by:

isTerminated in interface BasePoolService

Returns:

true if the object pool is terminated

isFair

public boolean isFair()

Returns the fairness setting of this object pool.

Specified by:

isFair in interface BasePoolService

Returns:

true if the object pool is fair to waiting taker threads