We have a service that runs on multiple servers. Clients connect to any of these servers to wait for some event. The connection between the client and server is long-polling style. Meaning the server will not respond, until there is event happening. The client will keep the connection open.
For example, we have servers: s1, s2, s3. We have client c1, which is connecting to s3 currently.
Now the problem is the event may be triggered on different servers. For example, someone connects to s1 and triggers some event. If that event is related to c1, how can s1 tell s3 that the event is ready and it should respond to c1 immediately?