So I have a Rails app (which in this case seems like it would be irrelevant, but I’ll mention it anyway). It’s a sort of chat room application.
In order to tell which users are currently in a chat room, I’ve been using Javascript polling.
So a simple
$(function() {
setTimeout(updateUsers, 15000);
});
where updateUsers just calls an AJAX get request to pull the array of users currently in the chatroom.
Here’s my question: 15 seconds is a pretty long time to wait to poll. How frequently should I do it without performance issues? Obviously it depends on a lot of factors, but I’d like to hear those factors. I’ve seen a bunch of similar questions for receiving messages in chat rooms, but none yet for lists of users, which is why I’m asking this question.
It depends on a ton of things, like your infrastructure, the number of expected users, etc. Even if we had those numbers, it’s hard to tell what would be a good timeout.
If you are only sending out a simple JSON array with the list of users, I’d say experiment with a 3-5 seconds delay and check from there. This is a problem of premature optimization- you’re trying to solve a problem you don’t yet have.
There are, however, two other possible solutions:
You could only send the difference. When you poll, you return a message saying which users have connected and which have left since the last polling. This requires some kind of server tracking, but can be done.
The other solution would be to not use polling at all, and use a more modern technology like WebSockets / Long-polling. Those will allow the server itself to send messages to your clients. As such, you can send them an initial list when they connect, and a single minimal message everytime someone else connects / leaves. A great solution to this in a Node environment is Socket.IO. I’m not much of a Ruby guy so I don’t know if anyone has done something similar but I wouldn’t be surprised if someone had ported the whole thing to Rails. Search around, I’m sure you’ll find something that fits your needs.