node.js: Javascript's in your backend

node.jsJavaScript’s in your backend David Padbury http://davidpadbury.com @davidpadbury

Programming 101

static void Main(){ int result = Add(2, 2); Console.WriteLine("2+2 = {0}", result);}static int Add(int n1, int n2){ return n1 + n2;}

static void Main(){ string name = GetName(); Console.WriteLine("Hi {0}", name);}static string GetName(){ return Console.ReadLine();}

Looks pretty much the same?

static void Main() Normal Method Call{ int result = Add(2, 2); Console.WriteLine("2+2 = {0}", result);}static int Add(int n1, int n2){ return n1 + n2;} Does some stuff in processor cache or RAM

static void Main() Normal Method Call{ string name = GetName(); Console.WriteLine("Hi {0}", name);}static string GetName(){ return Console.ReadLine();} Blocks until ready

What’s the big deal?Well, let’s think about what we do in a web server...

public ActionResult View(int id){ var product = northwindDataContext.Get(id); return View(product);} Blocking Network Call (IO)

Think about what we really do on a web server...

Call Databases Grab Files Think about what we really do on a web server...Pull from caches Wait on other connections

It’s all I/O

CPU Cycles L1 3 L2 14 RAM 250 Disk 41,000,000Network 240,000,000 0 75,000,000 150,000,000 225,000,000 300,000,000 http://nodejs.org/jsconf.pdf

Comparatively, I/O pretty much takes forever...

And yet, we write code exactly the same.

“we’re doing it wrong” - Ryan Dahl, node.js creatorhttp://www.yuiblog.com/blog/2010/05/20/video-dahl/

So I can guess what you’re thinking, “What about multi-threading?”

Yep, mainstream web servers like Apache and IIS* use a Thread Per Connection* Well, technically IIS doesn’t quite have a thread per connection as there’s some kernel level stuff which will talk to IIS/ ASP.NET depending on your conﬁguration and it’s all quite complicated. But for the sake of this presentation we’ll say it’s a thread per connection as it’s pretty darn close in all practical terms. If you’d like to talk about this more feel free to chat to me afterwards, I love spending my spare time talking about threading in IIS. HONEST.

Threading ain’t freeContext Switching Execution Stacks take Memory

Sure - but what else?

An Event LoopUse a single thread - do little pieces of work, and do ‘em quickly

With an event loop, you ask itto do something and it’ll get back to you when it’s done

But, a single thread?

nginx is event based (higher is better)http://blog.webfaction.com/a-little-holiday-present

(lower is better)http://blog.webfaction.com/a-little-holiday-present

Being event based is actually a pretty good way of writing heavily I/O bound servers

So why don’t we?

We’d have to completely change how we write code public ActionResult View(int id) { var product = northwindDataContext.Get(id); return View(product); Blocking Call }

To something where we could easily write non-blocking code public void View(HttpResponse response, int id) { Non-blocking Call northwindDataContext.Get(id, (product) => { response.View(product); }); } Anonymous Function Callback

CMost old school languages can’t do this

*cough*Java *cough*

Even if we had a language that madewriting callbacks easy (like C#), we’d need a platform that had minimal to no blocking I/O operations.

If only we had a language which was designed to be inherently single threaded, had ﬁrst class functions and closures built in, and had no preconceived notions about I/O? Wouldn’t it also be really handy if half* of the developers in the world already knew it? (you can probably guess where this is going...) *The guy speaking completely made that up for the sake of this slide. but he’s pretty sure there are quite a few

http://nodejs.org/

Node.js is a set of JavaScript bindings forwriting high-performance network servers

With the goal of making developing high- performance network servers easy

Built on Google’s V8 js engine (so it’s super quick)

Exposes only non-blocking I/O API’s

Stops us writing code that behaves badly

DemoBasic node.js

console.log(Hello);setTimeout(function() { console.log(World);}, 2000);

Prints Immediately $node app.js Hello Waits two seconds World $ Exits as there’s nothing left to do

Node comes with a large set of libraries

Node comes with a large set of libraries Timers Processes Events BuffersStreams Crypto File System REPL Net HTTP HTTPS TLS/SSL DNS UDP/Datagram

Libraries are ‘imported’ using the require function

Just a function call var http = require(http), fs = require(fs);Returns object exposing the API

DemoRequire and standard modules

Every request is just a callbackvar http = require(http);var server = http.createServer(function(req, res) { res.writeHead(200, { Content-Type: text/plain }); res.end(Hello from node.js!);});server.listen(3000);console.log(Server started on 3000);

Node libraries are structured as CommonJS moduleshttp://www.commonjs.org/specs/modules/1.0/

Libraries are evaluated in their own contextOnly way to share API is to attach to exports

require function returns exports

DemoWriting custom modules

/* people.js */function Person(name) { this.name = name;}Person.prototype = { sayHi: function() { console.log("Hi, Im " + this.name); }} Attaching API to exportsexports.createPerson = function(name) { return new Person(name);};

exports from module are returnedvar people = require(./people); File pathvar barry = people.createPerson(Barry);barry.sayHi(); // Hi, Im Barryconsole.log( typeof Person ); // undefined Internals of module don’t exist in this context

Despite being a relatively new runtime,there are a massive number of open source libraries available

Ofﬁcial list alone has 718 released modules https://github.com/ry/node/wiki/modules (as of Feb 2011)

Modules for just about everything you could think of, •Web Application Servers •Static File Servers •Web Middleware •Database (couchdb, mongodb, mysql, postgres, sqlite, etc..) •Templating •Build & Production •Security •SMTP •TCP/IP •Web Services •Message Queues •Testing •XML •Command Line Parsers •Parser Generators •Debugging tools •Compression •Graphics •Payment Gateways •Clients for many public API’s (facebook, ﬂickr, last.fm, twitter, etc...) •Internationalization and probably a lot for things you’ve never heard of

So you can just pull them down and reference them on their ﬁles. However once libraries start depending onother libraries, and we start installing quite a few, Well, we know how this ends up...

Established platforms have tools to help with this Node is no different

npm is a package manager fornode. You can use it toinstall and publish yournode programs. It managesdependencies and does othercool stuff. http://npmjs.org/

$npm install <name>

Module details and dependencies are expressed in CommonJS standard package.json http://wiki.commonjs.org/wiki/Packages/1.0

{ "name" : "vows", "description" : "Asynchronous BDD & continuousintegration for node.js", "url" : "http://vowsjs.org", "keywords" : ["testing", "spec", "test", "BDD"], "author" : "Alexis Sellier <self@cloudhead.net>", "contributors" : [], "dependencies" : {"eyes": ">=0.1.6"}, "main" : "./lib/vows", "bin" : { "vows": "./bin/vows" }, "directories" : { "test": "./test" }, "version" : "0.5.6", "engines" : {"node": ">=0.2.6"}} https://github.com/cloudhead/vows/

Okay.So node’s a nice idea in theory and there’s enough there to be compared to other established platforms. But where does it rock?

Web apps are growing up

In my mind, there are two major challengesfacing the next generation of web applications.

Being real-time

Being everywhere

Most web application platforms struggle, or at least don’t much help with these challenges

Node.js does

Being everywhere

Although it’s nice to think about writing applications for just new versions of Chrome, Firefox and IE9. We should strive to get our applications working everywhere*. *to at least some degree

And I’m not just talking about

Browsers are everywhere

With traditional web applications there are two distinct sidesClient Server

With node.js both sides speak the samelanguage making it easier to work together

The server can help thebrowser ﬁll out functionality that it’s missing

DemojQuery on the Server using jsdom

var jsdom = require(jsdom), window = jsdom.jsdom().createWindow(), document = window.document, htmlEl = document.getElementsByTagName(html)[0];jsdom.jQueryify(window, function() { var $ = window.jQuery; $(<div />).addClass(servermade).appendTo(body); $(.servermade).text(And selectors work fine!); console.log( htmlEl.outerHTML );});

DemoSharing code between Server and Client

Being real-time

HTTP RequestClient Server Response

Not so good for pushingClient Server Update. Erm.... Fail

Web SocketsProper Duplex Communication!

But it’s only in very recent browsersAnd due to protocol concerns it’s now disabled even in recent browsers

But you’ve probably noticed thatapplications have been doing this for years We’ve got some pretty sophisticated methods of emulating it, even in IE

WebSockets Silverlight / FlashIE HTML Document ActiveX AJAX Long Polling AJAX multipart streaming Forever IFrame JSONP Polling

All of those require a server holding open a connection for as long as possible.

Thread-per-connection web servers struggle with this

Node.js doesn’t even break a sweat

var socket = io.listen(server);socket.on(connection, function(client){ // new client is here! client.on(message, function(){ … }) client.on(disconnect, function(){ … })});

DemoReal-time web using socket.io

var socket = io.listen(server), counter = 0;socket.on(connection, function(client) { No multithreading, so no counter = counter + 1; race condition! socket.broadcast(counter); client.on(disconnect, function() { counter = counter - 1; socket.broadcast(counter); });});

Node.js is young, but it’s growing up fast

So how do you get started with node?

If you’re on Mac or Linux then you’re good to go http://nodejs.org/

If you’re on Windowsyou’re going to be a little disappointed

Currently the best way to get start on Windows is hosting inside a Linux VM and ssh’ing it.http://www.lazycoder.com/weblog/2010/03/18/getting-started-with-node-js-on-windows/ Proper Windows support will be coming soon. http://nodejs.org/v0.4_announcement.html

I think that node is super exciting and that you should start experimenting with it today

But even if you don’t, other WebFrameworks are watching and it will almost certainly inﬂuence them

http://nodejs.org/http://groups.google.com/group/nodejs #nodejs on freenode.net http://howtonode.org/https://github.com/alexyoung/nodepad

Questions?

// Thanks for listening!return;

Image AttributionsOld man exmouth market, Daniel2005 - http://www.flickr.com/photos/loshak/530449376/needle, Robert Parviainen - http://www.flickr.com/photos/rtv/256102280/Skeptical, Gabi in Austin - http://www.flickr.com/photos/gabrielleinaustin/2454197457/Javascript!=Woo(), Aaron Cole - http://www.flickr.com/photos/awcole72/1936225899/Day 22 - V8 Kompressor, Fred - http://www.flickr.com/photos/freeed/5379562284/The Finger, G Clement - http://www.flickr.com/photos/illumiquest/2749137895/A Messy Tangle of Wires, Adam - http://www.flickr.com/photos/mr-numb/4753899767/7-365 I am ready to pull my hair out..., Bram Cymet - http://www.flickr.com/photos/bcymet/3292063588/Epic battle, Roger Mateo Poquet - http://www.flickr.com/photos/el_momento_i_sitio_apropiados/5166623452/Worlds Tiniest, Angelina :) - http://www.flickr.com/photos/angelinawb/266143527/A Helping Hand, Jerry Wong - http://www.flickr.com/photos/wongjunhao/4285302488/[108/365] Ill-advised, Pascal - http://www.flickr.com/photos/pasukaru76/5268559005/Gymnastics Artistic, Alan Chia - http://www.flickr.com/photos/seven13avenue/2758702332/metal, Marc Brubaker - http://www.flickr.com/photos/hometownzero/136283072/Quiet, or Youll see Father Christmas again, theirhistory - http://www.flickr.com/photos/22326055@N06/3444756625/Day 099, kylesteed - http://www.flickr.com/photos/kylesteeddesign/4507065826/Spectators in the grandstand at the Royal Adelaide Show, State Library of South Australia - http://www.flickr.com/photos/state_library_south_australia/3925493310/

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node.js: Javascript's in your backend

by David Padbury on Feb 20, 2011

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node.js: Javascript’s in your backend — Presentation Transcript