Distributed Multiple Readers/Single Writer Locks using Hazelcast

This library uses Hazelcast's distributed data structures to create two java.util.concurrent.locks.ReadWriteLock implementations. DistributedReadWriteLock is not reentrant. DistributedReentrantReadWriteLock is strongly reentrant (holders of write locks can acquire additional read locks.)

A running Hazelcast cluster is required. The integration tests in the test folder demonstrate a simplistic way to create a usable cluster of two nodes on localhost, but you can use any method you wish.

Usage

Assuming you have a HazelcastInstance, usage is identical to usage of java.util.concurrent.locks.ReentrantReadWriteLock, with the exception of creation of a new lock instance.

// This can be a singleton, but additional instances aren't a problem.
DistributedLockFactory lockFactory =
    DistributedLockFactory.newHazelcastLockFactory(hazelcastInstance);

ReadWriteLock lock = lockFactory.getReentrantReadWriteLock("myLock");
lock.readLock().lock();
try {
    // do some stuff
}
finally {
    lock.readLock.unlock();
}

Note that not all methods are supported for all Lock types. For example, neither lock supports newCondition(), and the reentrant lock does not support lockInterruptibly(), or untimed tryLock() due to limitations imposed by Hazelcast's ICondition.await() method. These methods will throw UnsupportedOperationException.