socket io really heavy load - node.js

Question

My nodejs server under heavy load for some reason, all i'm running is a small app using socket io. This app mainly gets text from a textarea on an html page and updates it to the people in the "room". Sort of like a live chat. However this is causing huge load on my server every time someone types something if theres 2 clients per room it will cause a lag spike.
server-side code
var app = require('http').createServer(handler)
var io = require('socket.io')(app);
var fs = require('fs');
app.listen(process.env.PORT);
function handler (req, res) {
fs.readFile(__dirname + '/index.html',
function (err, data) {
if (err) {
res.writeHead(500);
return res.end('Error loading index.html');
}
res.writeHead(200);
res.end(data);
});
}
io.on('connection', function (socket) {
socket.on('join_room',function(room){
socket.join(room);
socket.in(room).emit('joined_room', 'true');
});
socket.on('blob', function (room) {
socket.in(room.name).emit('new_text', room.update_text);
});
socket.on('blob-typing',function(room){
socket.in(room.name).emit('some_typing', {cur_loc:room.cursor_location});
});
});
client-side code
var socket = io.connect('x');
socket.emit('join_room',url_key);
setInterval(function(){
if (field_change === true) {
var post_data = {
name: url_key,
update_text: $('.blob').val()
};
socket.emit('blob', post_data);
post_data = {
name: url_key,
cursor_location:0
};
socket.emit('blob-typing', post_data);
}
field_change = false;
},1000);
$(".blob").on('keyup paste input',function () {
delay(function(){
field_change = true;
},500);
});
socket.on('joined_room',function(data){
});
var delay = (function(){
var timer = 0;
return function(callback, ms){
clearTimeout (timer);
timer = setTimeout(callback, ms);
};
})();
Please advise as to how i can fix the load, any technique or strategy would be much appreciated!