WebSocketService could be more cluster aware #461
Description
Right now, when you call the public methods on WebSocketService, it will only consider Connections managed by the current instance. But it would be potentially more useful in some cases to have WebSocketService delegate to the other servers to broadcast messages more widely.
This has come up in one client, where we want a particular instance to invalidate some client-side state and notify all connected clients in the cluster. In that case we have to do an extra bit of work to push a message to each instance, and have that instance notify
Not clear if we need a set of parallel cluster aware method (e.g pushToClusterChannels()) or just make the existing methods smart enough to pass on requests for unknown channels to the appropriate instance. In any case, it might ease the implementation to incorporate the instance id in to the channel key.
Also would be useful to be able to broadcast easily to all channels -- e.g. pushToAllChannels()