How to handle multiple chat sessions with Node.js - node.js

Question

I am currently developing a chat system using Node.js. My question is, how do I handle multiple chat sessions with Node.js. That's a bit vague so I'll explain...
So for example two people might engage in a chat session. Node.js checks every couple of seconds for new messages. This is simple enough as I can get this to work fine using my code below.
My issue is when another two people at the same time are in another chat session.
At present I am sending two query strings called "chat_id" and "check_date" so it can check for new chat messages after a certain date and time.
Problem is, the "chat_id" and "check_date" are overwritten every time a new chat is started because the server is being used by both chat rooms.
Am I making sense?
My code below:
var chat_id, check_date;
var sys = require("sys"),
http = require("http"),
url = require("url"),
path = require("path"),
fs = require("fs"),
events = require("events");
// Conntect to database
var Client = require('mysql').Client;
var client = new Client();
client.host = 'localhost';
client.port = 3306;
client.database = '****';
client.user = '****';
client.password = '****';
client.connect(function(error, results) {
if(error) {
console.log('Connection Error: ' + error.message);
return;
}
console.log('Connected to MySQL');
});
// Check for chat updates
function getChatUpdates() {
if (typeof(check_date) == 'undefined')
return;
client.query('SELECT name, message FROM chat WHERE chat_id = "' + chat_id + '" AND date_entered > "' + check_date + '"',
function selectCb(error, results, fields) {
if (error) {
console.log('GetData Error: ' + error.message);
client.end();
return;
}
if (results.length > 0) {
for(var i = 0;i<results.length;i++) {
console.log('Name: ' + results[i]['name']);
console.log('Message: ' + results[i]['message']);
}
}
});
}
// Set interval to check for chat updates every 2 seconds
setInterval(getChatUpdates, 2000);
http.createServer(function(request, response) {
// Get the query strings
var uri = url.parse(request.url, true);
chat_id = uri.query.chat_id;
check_date = uri.query.check_date;
console.log('Chat ID: ' + chat_id);
console.log('Last Check: ' + check_date);
// we'll do something here later.
}).listen(8080);
sys.puts("Server running at http://localhost:8080/");

Answer 1

It seems like you are having a PHP background and when programming in node.js you should have a completely different mindset. You should not poll(setInterval(getChatUpdates, 2000);
) for messages, but push(callbacks/events) messages to users on event. I advice you to have a look at socket.io and use a in-memory database like redis(instead of mysql) to store your messages. When you code like this your site will perform much better and is going to be real-time(more). Also I would advice you to use express as your framework to develop websites instead of using raw http module. I don't know if you already know about npm, but you should use that to manage your dependencies.

Answer 2

var chat_id, check_date;
Are global variables. You are going to be overriding the chat_id on every connection (in createServer. You probably need some sort of session storage (to associate a user and their chat) eg. an Array, Redis, etc.

Answer 3

It looks like you trying to use MySQL as message queue. RabbitMQ?