RSNA 2012 & Dxlive!

wHAT aRE WEBSOCKETS?

Enter Socket.io

Just the facts, ma'am

Who is using Node.js?

What is Event-driven I/o?

Web servers like Apache that are used to serve PHP and other CGI scripts are thread based because they spawn a system thread for every incoming request. While this is fine for many applications, the thread based model does not scale well with many long-lived connections like you would need in order to serve real-time applications like Friendfeed or Google Wave.

That's Nice, but what is it good for?

Simply Put, shifting around data

Whereas traditional multithreaded systems are suited to heavy CPU work, event-driven systems are meant for network applications that involve heavy I/O.

Quick Benchmark

var i, a, b, c, max;
max = 1000000000;
var d = Date.now();
for (i = 0; i < max; i++) {
    a = 1234 + 5678 + i;
    b = 1234 * 5678 + i;
    c = 1234 / 2 + i;
}
console.log(Date.now() - d);

$a = null;
$b = null;
$c = null;
$i = null;
$max = 1000000000;
$start = microtime(true);
for ($i = 0; $i < $max; $i++) {
    $a = 1234 + 5678 + $i;
    $b = 1234 * 5678 + $i;
    $c = 1234 / 2 + $i;
}
var_dump(microtime(true) - $start);

Results (MS)

Javascript, the four letter word

You're forced into this non-blocking style. Anytime you want to talk to this remote back end or something, you have to give a callback. You can't say 'Database give me the result and then in the next line use the result.' You have to somehow have a callback, so you get indented a bit or you jump into a different function. ~ Ryan Dahl

JavaScript is extremely well suited to event-based programming because it has anonymous functions and closures which make defining inline callbacks a cinch, and JavaScript developers already know how to program in this way.

cALLBACK hELL

It's an event loop, the right way to make a high-performance server. It's JavaScript, a high-level language. It has great support for closures, which you need for the callbacks in an event-based system. And you've got Google behind V8 in the JavaScript arms race.