When should I call Naming.unbind()?

Question

I have some code which I am making available via RMI.

If my program terminates abnormally, I won't have called Naming.unbind(), and a reference to the object will presumably be hanging around in the RMI registry, and subsequent calls to Naming.bind() with the same name will fail.

How do I make sure that rogue references are cleared up?

Answer 1

There is something called Distributed Garbage Collector (DGC). It uses leases to track stale bindings and will collect them once they are not used. Set the leaseValue system property of the exporting JVM to determine when a binding expires.

Setting the value to too low would result in increased network traffic. Setting it too high will result in stale references being held too long. You can call an idempotent method after lookup on the client side just to make sure the object is live (or use something like the Weblogic smart stubs). On the server side, you can check the registry and if a binding exist either unregister it (in case it's stale), dispose the remote object and export a new one or just leave it (if it's live).