EJB 3.1 singleton in cluster

Question

I didn't find much information about EJB 3.1 Singletons in cluster enviroment. Is it true that specification says that those singletons will guarantee one instance per JVM - so one per cluster node. Not one per whole cluster?

Answer 1

Yes, section 4.8 of the EJB 3.1 specification states that "each application will have one bean instance of the Singleton for each JVM".

Answer 2

The singleton itself does not guarantee one instance per cluster. For that you need to specify a dependency. If you are using jboss then it is "jboss.ha:service=HASingletonDeployer,type=Barrier".