How to lock a java method to protect multiple invocations

Question

I have an application that every 15 minutes or so does a replication from a remote database. It just keeps the two repositories in sync. Once this replication is going it is not possible to do it again. I have setup the following structure but I'm not sure if it is the correct approach.

public class ReplicatorRunner {

       private static Lock lock = new ReentrantLock();

       public replicate() {

           if (lock.tryLock()) {
               try {
                   // long running process
               } catch (Exception e) {                   
               } finally {
                   lock.unlock();
               }               
           } else {
               throw new IllegalStateException("already replicating");
           }

       }

}

public class ReplicatorRunnerInvocator {

    public void someMethod() {

        try {
            ReplicatorRunner replicator = new ReplicatorRunner();
            replicator.replicate();
        } catch (IllegalStateException e) {
            e.printStackTrace();
        }

    }

}

The ReplicatorRunner is the class owning the method replicate which can only be run one at a time.

Edit. I need the next call to fail (not block) if the method is already running on any instance.

Answer 1

This looks good. ReentrantLock.tryLock() will only give the lock to one thread, so synchronized is not necessary. It also prevents the blocking inherent in synchronization that you say is a requirement. ReentrantLock is Serializable, so should work across your cluster.

Go for it.