alluxio.resource

Class ResourcePool<T>

java.lang.Object

alluxio.resource.ResourcePool<T>

Type Parameters:

T - the type of resource this pool manages

All Implemented Interfaces:

Pool<T>, Closeable, AutoCloseable

Direct Known Subclasses:

BlockMasterClientPool, JobMasterClientPool

@ThreadSafe
public abstract class ResourcePool<T>
extends Object
implements Pool<T>

Class representing a pool of resources to be temporarily used and returned. Inheriting classes must implement the close method as well as initialize the resources in the constructor. The implemented methods are thread-safe and inheriting classes should also written in a thread-safe manner. See FileSystemMasterClientPool as an example.

Field Summary

Fields

Modifier and Type	Field and Description
protected AtomicInteger	mCurrentCapacity It represents the total number of resources that have been created by this pool.
protected int	mMaxCapacity
protected ConcurrentLinkedQueue<T>	mResources

Constructor Summary

Constructors

Modifier	Constructor and Description
	ResourcePool(int maxCapacity) Creates a ResourcePool instance with the specified capacity.
protected	ResourcePool(int maxCapacity, ConcurrentLinkedQueue<T> resources) Internal constructor that can provide an object to be used for the internal queue.

Method Summary

Modifier and Type	Method and Description
T	acquire() Acquires an object of type T from the pool.
T	acquire(long time, TimeUnit unit) Acquires an object of type {code T} from the pool.
abstract void	close() Closes the resource pool.
abstract T	createNewResource() Creates a new resource which will be added to the resource pool after the user is done using it.
void	release(T resource) Releases an object of type T, this must be called after the thread is done using a resource obtained by acquire.
int	size()

Methods inherited from class java.lang.Object

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

Field Detail

mMaxCapacity

protected final int mMaxCapacity

mResources

protected final ConcurrentLinkedQueue<T> mResources

mCurrentCapacity

protected final AtomicInteger mCurrentCapacity

It represents the total number of resources that have been created by this pool.

Constructor Detail

ResourcePool

public ResourcePool(int maxCapacity)

Creates a ResourcePool instance with the specified capacity.

Parameters:

maxCapacity - the maximum of resources in this pool

ResourcePool

protected ResourcePool(int maxCapacity,
                       ConcurrentLinkedQueue<T> resources)

Internal constructor that can provide an object to be used for the internal queue.

Parameters:

maxCapacity - bhe maximum of resources in this pool

resources - blocking queue to use

Method Detail

acquire

public T acquire()

Acquires an object of type T from the pool. This operation is blocking if no resource is available. Each call of acquire() should be paired with another call of release(Object)} after the use of this resource completes to return this resource to the pool.

Specified by:

acquire in interface Pool<T>

Returns:

a resource taken from the pool

acquire

@Nullable
public T acquire(long time,
                           TimeUnit unit)

Acquires an object of type {code T} from the pool. This method is like acquire(), but it will time out if an object cannot be acquired before the specified amount of time.

Specified by:

acquire in interface Pool<T>

Parameters:

time - an amount of time to wait, <= 0 to wait indefinitely

unit - the unit to use for time, null to wait indefinitely

Returns:

a resource taken from the pool, or null if the operation times out

close

public abstract void close()
                    throws IOException

Closes the resource pool. After this call, the object should be discarded. Inheriting classes should clean up all their resources here.

Specified by:

close in interface Closeable

Specified by:

close in interface AutoCloseable

Throws:

IOException

release

public void release(T resource)

Releases an object of type T, this must be called after the thread is done using a resource obtained by acquire.

Specified by:

release in interface Pool<T>

Parameters:

resource - the resource to be released, it should not be reused after calling this method

size

public int size()

Specified by:

size in interface Pool<T>

Returns:

the current pool size

createNewResource

public abstract T createNewResource()

Creates a new resource which will be added to the resource pool after the user is done using it. This method should only be called when the capacity of the pool has not been reached. If creating the resource will take a significant amount of time, the inheriting class should avoid calling this method and instead initialize all the resources in the constructor.

Returns:

a resource which will be added to the pool of resources