using socket io to get updates - node.js

Question

i'm using in socket.io to get live updates from database.
here is my code:
var q = "SELECT * FROM notifications";
db.query(q, function(err, rows, fields) {
if(rows[0]) {
io.sockets.emit('newNotifications', rows[0]);
}
});
its work, but i want to add WHERE userid = "+myuserid+"
the question is how to do this?
i tried to do this with this code:
socket.on('connect', function () {
socket.send({"myuserid":"1"});
console.log('connected');
});
thanks.

Answer 1

You basically need to tie a userid to a particular a particular socket. How you do this is dependent on how you're handling authentication.
Once you have a userid attached to the socket, you have a couple options for getting them individual notifications. The most straightforward is to do as you wanted above. Create a query with a condition limiting the results. You need to do this on a per-socket basis though, so you'll need something like the following.
data.watchForNotification = function(userId, fn) {
// Please sanitize this and make sure you're not vulnerable to sql injection attacks
var q = "SELECT ... WHERE UserId = " + userId;
data.watchedUsers[userId] = setInterval(function() {
db.query(q, function(err, rows, fields) {
if(rows.[0]) {
fn(rows[0]);
}
});
}, 10000);
}
data.stopWatching(userId) {
if(data.watchedUsers[userId]) {
clearInterval(data.watchedUsers[userId]);
delete data.watchedUsers[userId];
}
}
io.on('connection', function(socket) {
// authenticate and set socket.userId
data.watchForNotifications(socket.userId, function(notification) {
socket.emit('notification', notification);
});
socket.on('disconnect', function() {
data.stopWatching(socket.userId);
});
});
This will setup an interval that checks every 10 seconds for new notifications and will send those to the connected socket when they come in. It will also stop the database queries for that user if they disconnect. There is a lot of pseudo code and abstraction work going on here, but it should be enough to get you where you want to go.