org.gearman.server.util

Class EqualsLock

java.lang.Object

org.gearman.server.util.EqualsLock

public class EqualsLock
extends Object

A simple lock based on the value of an object instead of the object's instance. The synchronizing problem in the server is that sometimes it's required to synchronize on a key value for a hash table. However, the key being used will never be the same instance from one thread to another, and synchronizing on the hash table itself will be too slow. Currently synchronization is done by this lock which locks based on Object value, not the Object's instance. Synchronization could have been done using primitive Objects, like Integers, but I decided not to because this program is designed to be embedded. That kind of synchronization may interfere with the wrapping program, possibly causing a deadlock that is impossible to find.

Author:

isaiah.v

Constructor Summary

Constructors

Constructor and Description
EqualsLock()

Method Summary

Methods

Modifier and Type	Method and Description
void	lock(Object key) Accrues a lock for the given key.
boolean	tryLock(Object key) Acquires the lock only if it is free at the time of invocation.
void	unlock(Object key) Releases the lock of the given key.

Methods inherited from class java.lang.Object

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

Constructor Detail

EqualsLock

public EqualsLock()

Method Detail

lock

public final void lock(Object key)

Accrues a lock for the given key. If this thread acquires a lock with key1, any subsequent threads trying to acquire the lock with key2 will block if key1.equals(key2). If key1.equals(key2) is not true, the subsequent thread will acquire the lock for key2 and continue execution.

Parameters:

key - The key

tryLock

public final boolean tryLock(Object key)

Acquires the lock only if it is free at the time of invocation. Acquires the lock if it is available and returns immediately with the value true. If the lock is not available then this method will return immediately with the value false.

Parameters:

key - The key to acquire the lock

Returns:

true if the lock was acquired, false if the lock was not acquired

unlock

public final void unlock(Object key)

Releases the lock of the given key. The lock is only released if the calling thread owns the lock for the given key

Parameters:

key - The key