Detecting Client Disconnect

Question

I am looking for a way to determine when a client connects and disconnects (especially the latter) from the grid. Two approaches come to mind:
1) Polling for something that appears/disappears when a client connects or disconnects. The most obvious candidate is a lock. This approach is inefficient because it requires polling. It also raises the issue of how clients are distinguished, although that is not difficult (e.g. - invocable increments a counter which is used as a basis for the key to lock).
2) Getting a notification when this happens - preferably in-grid. However, I could find no listener for either the client connect/disconnect event or for locking. Likewise, using custom cache implementations (overriding a class and calling it out in the cache config) doesn't seem to provide notification of either locking, or (an alternate approach) the registration of a listener.
Overriding a cache indeed provides notice of listener registration, but it appear to be a general listener which is feeding some other internal Coherence facility which manages the specific per-client listeners.

Answer 1

Answering my own question, after research and help from Gene Glyzer:
There are a couple of ways to do this:
1) A client can lock a phantom (or real) entry in a cache. When the client member of the cluster goes away, the lock will be released.
2) Tracking cluster members:
* Add a listener:*service = CacheFactory.getService("name").addMemberListener(...)*
* Get the membership information (synchronously guard against listener events):*Set members = service.getServiceMembers()*
* Use subsequent listener events to adjust the members set.