RMI client tracking

I'm building a Client / Server app that has some very specific needs. There are 2 kinds of servers: the first kind provide most of the remote procedures and clients connect to these directly, while the second kind is a开发者_开发技巧 single server that should keep track of what users are active (clients) and how many servers of the first kind are active when a method is called.

The main thing is that the monitor should ONLY connect to the servers and not the clients directly. My first idea was to implement a simple login/logout rmi method when a client connects/ disconnects and keep track of those in a list but the main problem is when a client or server end abnormally.

For example, if a client goes offline abruptly the server should somehow be notified and update the list accordingly, while if a server goes out all of the clients connected to it should be marked as not active in the control server.

Any ideas of how to implement this functionality would be appreciated.

I would suggest implementing a "session" approach to the problem, where the servers and the clients are sending a "heartbeat" method call to the monitoring server every several minutes(may seconds or hours depending on your needs). If the monitoring server doesn't receive a "heartbeat" from the servers or clients in a certain amount of time, then you consider them gone (terminated abnormally) and notify accordingly.

Zookeeper may be something to look at. Have each clientserver register an ephemeral node for itself, and for each client that is connected to it. When the clientserver goes down, the ephemeral nodes will die. The monitor server just needs to watch zookeeper to see who is up and connected.

For detecting clients going down, you will need some kind of hearbeating so that the clientserver can detect when a client dies. If the client can talk to zookeeper directly, then simply have the client register an ephemeral node in zookeeper as well, and the clientserver can watch the clients ephemeral node, and know when the client is down.