How to make a node.js server with rooms scalable

Question

I have designed a Node.JS server that allows users to log in, join a room and exchange data with other users in this room using websockets. However I am now looking for a way to make this setup scalable.

I spend all afternoon researching various loadbalancers such as nginx and haproxy, but I still can't figure out how to organise my setup.

Initally users can login and view the active rooms. No biggie to makes this part scalable. However then they can join a specific room and at that point they need to be connected to the same node.js instance as the others in the room. It's this part I have trouble figuring out.

For now my solution exists out of creating two different types of node.js instances. One generic type to handle the login and room overview request methods and one roomtype that handle a number of rooms. The generic type then keeps track of which specific instance is responsible for which room and can deliver the correct address to the user's application.

However I am not satisfied with this solution, so I am open for suggestions. I understand that this is a rather vague question, but I am not looking for a exact solution, rather hints as to how to organize everything.

Answer 1

udidu touched on a possible solution, but to expand, you should look at a scalable pub/sub solution; Redis, a popular data store, has pub/sub built in and I use it often to great effect.

Using Redis (or some other system) to help make sure every instance of your Node.js app receives information about who's chatting in which room removes the dependency that all users in a room are connected to the same Node.js instance.