alluxio.resource

Class DynamicResourcePool<T>

java.lang.Object

alluxio.resource.DynamicResourcePool<T>

Type Parameters:

T - the type of the resource

All Implemented Interfaces:

Pool<T>, Closeable, AutoCloseable

Direct Known Subclasses:

AbstractHiveClientPool, BlockMasterClientPool, BlockWorkerClientPool, FileSystemMasterClientPool

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

A dynamic pool that manages the resources. It clears old resources. It accepts a min and max capacity. When acquiring resources, the most recently used resource is returned.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	DynamicResourcePool.Options Options to initialize a Dynamic resource pool.
protected class	DynamicResourcePool.ResourceInternal<R> A wrapper on the resource to include the last time at which it was used.
static class	DynamicResourcePool.SelectionPolicy A policy specifying in what order to pick a resource item from a pool.

Field Summary

Fields

Modifier and Type	Field and Description
protected java.time.Clock	mClock
protected ConcurrentHashMap<T,DynamicResourcePool.ResourceInternal<T>>	mResources
protected DynamicResourcePool.SelectionPolicy	mSelectionPolicy the selection policy of the resource pool.

Constructor Summary

Constructors

Constructor and Description
DynamicResourcePool(DynamicResourcePool.Options options) Creates a dynamic pool instance.

Method Summary

Modifier and Type	Method and Description
T	acquire() Acquires a resource of type {code T} from the pool.
T	acquire(long time, TimeUnit unit) Acquires a resource of type {code T} from the pool.
void	close() Closes the pool and clears all the resources.
protected abstract void	closeResource(T resource) Closes the resource.
protected abstract T	createNewResource() Creates a new resource.
protected abstract com.codahale.metrics.Counter	getMetricCounter()
protected abstract boolean	isHealthy(T resource) Checks whether a resource is healthy or not.
void	release(T resource) Releases the resource to the pool.
protected abstract boolean	shouldGc(DynamicResourcePool.ResourceInternal<T> resourceInternal)
int	size()

Methods inherited from class java.lang.Object

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

Field Detail

mSelectionPolicy

protected final DynamicResourcePool.SelectionPolicy mSelectionPolicy

the selection policy of the resource pool. see DynamicResourcePool.SelectionPolicy for details

mResources

protected final ConcurrentHashMap<T,DynamicResourcePool.ResourceInternal<T>> mResources

mClock

protected java.time.Clock mClock

Constructor Detail

DynamicResourcePool

public DynamicResourcePool(DynamicResourcePool.Options options)

Creates a dynamic pool instance.

Parameters:

options - the options

Method Detail

getMetricCounter

protected abstract com.codahale.metrics.Counter getMetricCounter()

acquire

public T acquire()
          throws IOException

Acquires a resource of type {code T} from the pool.

Specified by:

acquire in interface Pool<T>

Returns:

the acquired resource

Throws:

IOException

acquire

public T acquire(long time,
                 TimeUnit unit)
          throws TimeoutException,
                 IOException

Acquires a resource 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

unit - the unit to use for time

Returns:

a resource taken from the pool

Throws:

TimeoutException - if it fails to acquire because of time out

IOException - if the thread is interrupted while acquiring the resource

release

public void release(T resource)

Releases the resource to the pool. It expects the resource to be released was acquired from this pool. release(Object) and acquire() must be paired. Do not release the resource acquired multiple times. The behavior is undefined if that happens.

Specified by:

release in interface Pool<T>

Parameters:

resource - the resource to release

close

public void close()
           throws IOException

Closes the pool and clears all the resources. The resource pool should not be used after this.

Specified by:

close in interface Closeable

Specified by:

close in interface AutoCloseable

Throws:

IOException

size

public int size()

Specified by:

size in interface Pool<T>

Returns:

the current pool size

shouldGc

protected abstract boolean shouldGc(DynamicResourcePool.ResourceInternal<T> resourceInternal)

Parameters:

resourceInternal - the resource to check

Returns:

true if the resource should be garbage collected

isHealthy

protected abstract boolean isHealthy(T resource)

Checks whether a resource is healthy or not.

Parameters:

resource - the resource to check

Returns:

true if the resource is healthy

closeResource

protected abstract void closeResource(T resource)
                               throws IOException

Closes the resource. After this, the resource should not be used. It is not guaranteed that the resource is closed after the function returns.

Parameters:

resource - the resource to close

Throws:

IOException

createNewResource

protected abstract T createNewResource()
                                throws IOException

Creates a new resource.

Returns:

the newly created resource

Throws:

IOException