alluxio.collections

Class LockPool<K>

java.lang.Object

alluxio.collections.LockPool<K>

Type Parameters:

K - key for the locks

All Implemented Interfaces:

Closeable, AutoCloseable

public class LockPool<K>
extends Object
implements Closeable

A resource pool specifically designed to contain locks and will NOT evict any entries that are in use. The pool size is unlimited, when the pool size is larger than the configured max size, a background thread will try to evict locks that are no longer locked, but if all the locks are locked, none of them will be evicted. In the worst case (e.g. deadlock), the pool size might keep growing until exhausting system memories.

Constructor Summary

Constructors

Constructor and Description
LockPool(java.util.function.Function<? super K,? extends ReentrantReadWriteLock> defaultLoader, int initialSize, int lowWatermark, int highWatermark, int concurrencyLevel) Constructor for a lock pool.

Method Summary

Modifier and Type	Method and Description
void	close()
boolean	containsKey(K key) Returns whether the pool contains a particular key.
LockResource	get(K key, LockMode mode) Locks the specified key in the specified mode.
RWLockResource	get(K key, LockMode mode, boolean useTryLock) Locks the specified key in the specified mode.
Map<K,ReentrantReadWriteLock>	getEntryMap()
ReentrantReadWriteLock	getRawReadWriteLock(K key) Get the raw readwrite lock from the pool.
int	size()
String	toString()
Optional<RWLockResource>	tryGet(K key, LockMode mode) Attempts to take a lock on the given key.

Methods inherited from class java.lang.Object

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

Constructor Detail

LockPool

public LockPool(java.util.function.Function<? super K,? extends ReentrantReadWriteLock> defaultLoader,
                int initialSize,
                int lowWatermark,
                int highWatermark,
                int concurrencyLevel)

Constructor for a lock pool.

Parameters:

defaultLoader - specify a function to generate a value based on a key

initialSize - initial size of the pool

lowWatermark - low watermark of the pool size

highWatermark - high watermark of the pool size

concurrencyLevel - concurrency level of the pool

Method Detail

close

public void close()
           throws IOException

Specified by:

close in interface Closeable

Specified by:

close in interface AutoCloseable

Throws:

IOException

get

public LockResource get(K key,
                        LockMode mode)

Locks the specified key in the specified mode.

Parameters:

key - the key to lock

mode - the mode to lock in

Returns:

a lock resource which must be closed to unlock the key

get

public RWLockResource get(K key,
                          LockMode mode,
                          boolean useTryLock)

Locks the specified key in the specified mode.

Parameters:

key - the key to lock

mode - the mode to lock in

useTryLock - Determines whether or not to use Lock.tryLock() or Lock.lock() to acquire the lock. Differs from tryGet(Object, LockMode) in that it will block until the lock has been acquired.

Returns:

a lock resource which must be closed to unlock the key

tryGet

public Optional<RWLockResource> tryGet(K key,
                                       LockMode mode)

Attempts to take a lock on the given key.

Parameters:

key - the key to lock

mode - lockMode to acquire

Returns:

either empty or a lock resource which must be closed to unlock the key

getRawReadWriteLock

public ReentrantReadWriteLock getRawReadWriteLock(K key)

Get the raw readwrite lock from the pool.

Parameters:

key - key to look up the value

Returns:

the lock associated with the key

toString

public String toString()

Overrides:

toString in class Object

containsKey

public boolean containsKey(K key)

Returns whether the pool contains a particular key.

Parameters:

key - the key to look up in the pool

Returns:

true if the key is contained in the pool

size

public int size()

Returns:

the size of the pool

getEntryMap

public Map<K,ReentrantReadWriteLock> getEntryMap()

Returns:

all entries in the pool, for debugging purposes