What happens to socket IDs when Node.js server restarts?

Question

I'm using Node.js with socket.io for a multiplayer game. There are game rooms and players can join different rooms. That part works fine.

Now, I want to be prepared for the possibility of the Node server crashing for whatever reason. I have Node backing up data to Redis, and if it crashes, it restarts automatically, fetches the data back from Redis and continues normal operation.

That's what I want anyway, but I'm confused about one thing. Since each socket is identified by its ID, how can the server know which user to subscribe to which room after a restart? Will the socket IDs still be valid? Or do they need to be re-assigned somehow (presumably based on unique user IDs)?

Answer 1

To be honest I have never worked with socket.io, but I have worked with sockjs. I don't know what are the implementation differences, but sockjs also has each connection identified by its own ID (which is a UUID, as far as I see it). But the ID changes every time a user reconnects, so I believe it is not a useful way to identify users.

Maybe you should store some fixed user identification (such as email address, username) and relocate the user by that parameter (that's what I'm doing usually).