Callback interface for Meta. You can supply an implementation of this to recieve notifications when servers are stopped or started. If an added callback ever throws an exception or goes away, it will be automatically removed. Please note that all callbacks are done asynchronously; murmur does not wait for the callback to complete before continuing processing.
Called when a server is started. The server is up and running when this event is sent, so all methods that need a running server will work.
Called when a server is stopped. The server is already stopped when this event is sent, so no methods that need a running server will work.