org.jmdware.ephemeral.locks

Class EphemeralLocks

java.lang.Object

org.jmdware.ephemeral.locks.EphemeralLocks

public class EphemeralLocks
extends Object

Balances parallelism with thread-safety by assigning different locks to different keys. This allows threads operating on different keys to simultaneously execute the critical section while threads operating on the same key execute the critical section serially. Memory usage grows with the number of active keys. Underlying lock instances are discarded when no longer needed.

Keys must implement Object.equals(Object) and Object.hashCode() correctly.

Example usage:

 private final EphemeralLocks locks = new EphemeralLocks();

 ...

 // The id for the thread-sensitive resource. E.g. directory name, document
 // id, user id, etc.
 String id = ...;

 // try-with-resources recommended to ensure the unlock occurs.
 try (Handle ignored = locks.lock(id)) {
     // critical section - do sensitive operations here
     ...
 }

 // try-finally works, too.
 Handle lockHandle = locks.lock(id);

 try {
     // critical section - do sensitive operations here
     ...
 } finally {
     lockHandle.close();
 }
 

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static interface	EphemeralLocks.Handle Handle to close the underlying lock for a given key.

Constructor Summary

Constructors

Constructor and Description
EphemeralLocks()

Method Summary

Modifier and Type	Method and Description
EphemeralLocks.Handle	lock(Object key) Acquires the lock for the given key and returns a handle to the lock, which must be closed to release the underlying lock.
int	size() Returns the number of active locks.

Methods inherited from class java.lang.Object

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

Constructor Detail

EphemeralLocks

public EphemeralLocks()

Method Detail

lock

public EphemeralLocks.Handle lock(Object key)

Acquires the lock for the given key and returns a handle to the lock, which must be closed to release the underlying lock. Blocks uninterruptibly until the lock is acquired.

Parameters:

key - identifies the resource requiring a lock

Returns:

handle for releasing the underlying lock

See Also:

Lock.lock()

size

public int size()

Returns the number of active locks.

Returns:

active locks count