Package org.apache.hadoop.fs.impl.prefetch

Class BoundedResourcePool<T>

java.lang.Object

org.apache.hadoop.fs.impl.prefetch.ResourcePool<T>

org.apache.hadoop.fs.impl.prefetch.BoundedResourcePool<T>

All Implemented Interfaces:

java.io.Closeable, java.lang.AutoCloseable

public abstract class BoundedResourcePool<T>
extends ResourcePool<T>

Manages a fixed pool of resources. Avoids creating a new resource if a previously created instance is already available.

Constructor Summary

Constructors

Constructor	Description
BoundedResourcePool(int size)	Constructs a resource pool of the given size.

Method Summary

Modifier and Type	Method	Description
T	acquire()	Acquires a resource blocking if necessary until one becomes available.
void	close()
protected void	close(T item)	Derived classes may implement a way to cleanup each item.
protected abstract T	createNew()	Derived classes must implement a way to create an instance of a resource.
int	numAvailable()	Number of items available to be acquired.
int	numCreated()	Number of items created so far.
void	release(T item)	Releases a previously acquired resource.
java.lang.String	toString()
T	tryAcquire()	Acquires a resource blocking if one is immediately available.

Methods inherited from class java.lang.Object

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

Constructor Detail

BoundedResourcePool

public BoundedResourcePool(int size)

Constructs a resource pool of the given size.

Parameters:

size - the size of this pool. Cannot be changed post creation.

Throws:

java.lang.IllegalArgumentException - if size is zero or negative.

Method Detail

acquire

public T acquire()

Acquires a resource blocking if necessary until one becomes available.

Specified by:

acquire in class ResourcePool<T>

Returns:

the acquired resource instance.

tryAcquire

public T tryAcquire()

Acquires a resource blocking if one is immediately available. Otherwise returns null.

Specified by:

tryAcquire in class ResourcePool<T>

Returns:

the acquired resource instance (if immediately available) or null.

release

public void release(T item)

Releases a previously acquired resource.

Specified by:

release in class ResourcePool<T>

Parameters:

item - the resource to release.

Throws:

java.lang.IllegalArgumentException - if item is null.

close

public void close()

Specified by:

close in interface java.lang.AutoCloseable

Specified by:

close in interface java.io.Closeable

Overrides:

close in class ResourcePool<T>

close

protected void close(T item)

Derived classes may implement a way to cleanup each item.

Overrides:

close in class ResourcePool<T>

Parameters:

item - the resource to close.

numCreated

public int numCreated()

Number of items created so far. Mostly for testing purposes.

Returns:

the count.

numAvailable

public int numAvailable()

Number of items available to be acquired. Mostly for testing purposes.

Returns:

the number available.

toString

public java.lang.String toString()

Overrides:

toString in class java.lang.Object

createNew

protected abstract T createNew()

Derived classes must implement a way to create an instance of a resource.

Specified by:

createNew in class ResourcePool<T>

Returns:

the created instance.