The document is a presentation about Node.js, a JavaScript runtime built on Chrome's V8 JavaScript engine. It discusses how Node.js uses an event-driven, non-blocking I/O model that makes it particularly suited for real-time web applications and I/O-intensive applications compared to traditional threaded server models. It provides examples of Node.js features like asynchronous I/O, event loops, modules and the npm package manager.

1. node.js
JavaScript’s in your backend
David Padbury
http://davidpadbury.com
@davidpadbury

2. Programming 101

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

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

5. Looks pretty much the same?

6. 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

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

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

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

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

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

12. It’s all I/O

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

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

15. And yet, we write code exactly the same.

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

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

18. 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.

19. Threading ain’t free
Context Switching Execution Stacks take Memory

20. Sure - but what else?

21. An Event Loop
Use a single thread - do little pieces of work, and do ‘em quickly

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

23. But, a single thread?

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

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

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

27. So why don’t we?

28. 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
}

29. 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

30. C
Most old school languages can’t do this

31. *cough*
Java
*cough*

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

33. 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

35. http://nodejs.org/

36. Node.js is a set of JavaScript bindings for
writing high-performance network servers

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

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

39. Exposes only non-blocking I/O API’s

40. Stops us writing code that
behaves badly

41. Demo
Basic node.js

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

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

44. Node comes with a large set of libraries

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

46. Libraries are ‘imported’ using the require function

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

48. Demo
Require and standard modules

49. Every request is just a callback
var 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');

50. var fs = require('fs'),
Doesn’t block to read file
http = require('http');
var server = http.createServer(function(req, res) {
fs.readFile('./data.txt', function(err, data) {
if (err) {
res.writeHead(500, { 'Content-Type': 'text/plain' });
res.end(err.message);
} else {
res.writeHead(200, { 'Content-Type': 'text/plain' });
res.end(data);
}
});
}); Server can deal with other requests while waiting for file
server.listen(3000);
console.log('Server listening on 3000');

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

52. Libraries are evaluated in their own context
Only way to share API is to attach to exports

53. require function returns exports

54. Demo
Writing custom modules

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

56. exports from module are returned
var people = require('./people'); File path
var barry = people.createPerson('Barry');
barry.sayHi(); // Hi, I'm Barry
console.log( typeof Person ); // undefined
Internals of module don’t exist in this context

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

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

59. 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

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

61. Messy

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

63. npm is a package manager for
node. You can use it to
install and publish your
node programs. It manages
dependencies and does other
cool stuff.
http://npmjs.org/

64. $npm install <name>

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

66. {
"name" : "vows",
"description" : "Asynchronous BDD & continuous
integration 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/

67. 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?

68. Web apps are growing up

69. In my mind, there are two major challenges
facing the next generation of web applications.

70. Being real-time

71. Being everywhere

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

73. Node.js does

74. Being everywhere

75. 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

76. And I’m not just talking about

77. Browsers are everywhere

78. With traditional web applications
there are two distinct sides
Client Server

79. With node.js both sides speak the same
language making it easier to work together

80. The server can help the
browser fill out functionality
that it’s missing

81. Demo
jQuery on the Server using jsdom

82. 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 );
});

83. Demo
Sharing code between Server and Client

84. (function(exports) {
exports.createChartOptions = function(data) {
var values = parseData(data);
return {
...
};
}
})(typeof window !== 'undefined' ? (window.demo = {}) : exports);
Attaches API to Attaches API to exports in node.js
window.demo in browser to be returned by require

85. Being real-time

86. HTTP
Request
Client Server
Response

87. Not so good for pushing
Client Server
Update. Erm....
Fail

88. Web Sockets
Proper Duplex Communication!

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

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

92. WebSockets
Silverlight / Flash
IE HTML Document ActiveX
AJAX Long Polling
AJAX multipart streaming
Forever IFrame
JSONP Polling

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

94. Thread-per-connection web
servers struggle with this

95. Node.js doesn’t even break a sweat

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

97. Demo
Real-time web using socket.io

98. 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);
});
});

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

100. So how do you get started with node?

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

102. If you’re on Windows
you’re going to be a little
disappointed

103. 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

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

105. But even if you don’t, other Web
Frameworks are watching and it will
almost certainly influence them

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

107. Questions?

108. // Thanks for listening!
return;

109. Image Attributions
Old 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/
World's 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 You'll 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/