Node.js - A practical introduction (v2)

A practical introduction

Felix Geisendörfer Munich Node.js User Group 01.12.2011 (v2)

@felixge

Twitter / GitHub / IRC

Felix Geisendörfer
(Berlin, Germany)

Feb 16, 2009

Ryan Dahl starts the node project (ﬁrst commit)

~June, 2009

Discovered node.js (v0.0.6)

Core Contributor

&

Module Author

node-mysql node-formidable

+ 30 other modules

Sep 29, 2009

Isaac Schlueter starts the npm package manager
(ﬁrst commit)

Nov 7, 2009

Ryan’s talk at JSConf.EU gets people excited about node

#1
Most watched repository on GitHub

0.6.3 was released 6 days ago (Nov 25)

Companies using node
• LinkedIn (Mobile Web App)
• Ebay (Data retrieval gateway)
• GitHub (for Downloads)
• Palm/HP (in WebOS)
• Yahoo! Mail
• Dow Jones & Company (for WJS social site)
• Rackspace (Cloudkick monitoring)
• Voxxer (Push to Talk mobile app)

Installing
$ git clone
git://github.com/joyent/node.git
$ cd node
$ git checkout v0.6.0
$ ./configure
$ sudo make install
(windows users: download node.exe)

Hello World

hello.js
console.log('Hello World');

Hello World

hello.js

$

Hello World

hello.js

$ node

Hello World

hello.js

$ node hello.js

Hello World

hello.js

$ node hello.js
Hello World

Hello World (REPL)

$ node
>

Hello World (REPL)

$ node
> console.log('Hello World')

Hello World (REPL)

$ node
> console.log('Hello World')
Hello World

Http Server
http_server.js
var http = require('http');
var server = http.createServer(function(req, res) {
res.end('Hi, how are you?');
});

server.listen(8080);

Http Server
http_server.js
});


$ node http_server.js

Http Server
http_server.js
});


$ node http_server.js $ curl localhost:8080
Hi, how are you?

“Come on, server side JS
has been around since
1996”

What is so special
about node?

Speed

• Node can do ~6000 http requests / sec per
CPU core (hello world, 1kb response,)

• It is no problem to handle thousands of
concurrent connections which are
moderately active

V8 JavaScript Engine

• Developed by Google in Aarhus, Denmark
for Google Chrome

• Translates JavaScript in Assembly Code

• Crankshaft JIT (enabled in 0.6.0 by default)

V8 JavaScript Engine

• You can expect to be within ~10x of C
performance usually

• Certain code can run within 2-3x of C

• Getting faster all the time

Blocking I/O
read_ﬁle_sync.js

var fs = require('fs');
var one = fs.readFileSync('one.txt', 'utf-8');
console.log('Read file one');
var two = fs.readFileSync('two.txt', 'utf-8');
console.log('Read file two');

Blocking I/O
read_ﬁle_sync.js


$ node read_file_sync.js

Blocking I/O
read_ﬁle_sync.js


Read file one

Blocking I/O
read_ﬁle_sync.js


Read file one
Read file two

Non-Blocking I/O
read_ﬁle_async.js
fs.readFile('one.txt', 'utf-8', function(err, data) {
});
fs.readFile('two.txt', 'utf-8', function(err, data) {
});

Non-Blocking I/O
read_ﬁle_async.js
});
});

$ node read_file_async.js

Non-Blocking I/O
read_ﬁle_async.js
});
});

Read file two

Non-Blocking I/O
read_ﬁle_async.js
});
});

Read file two
Read file one

Blocking I/O

Read one.txt (20ms)

Read two.txt (10ms)

Total duration (30ms)

Non-Blocking I/O

Read one.txt (20ms)

Read two.txt (10ms)

Total duration (20ms)

Non-Blocking I/O
• Close to ideal for high concurrency / high
throughput, single execution stack

• Forces you to write more efﬁcient code by
parallelizing your I/O

• Feels pretty much like AJAX in the browser

WebSockets

• Persistent connection between browser/server

• Very hard / awkward to do on traditional stacks

• Hard to scale on traditional stacks

Socket.IO (community module)
• WebSocket

• Adobe® Flash® Socket

• AJAX long polling

• AJAX multipart streaming

• Forever Iframe

• JSONP Polling

Chooses most capable transport at runtime!

“Streams are to time as arrays are to space.”
-- Jed Schmidt @ JSConf.eu 2010

Streams in node.js

• Readable

• Writable

• Both

Streams
req.on('data', console.log);
});

Streams
req.on('data', console.log);
});

$ node stream.js &
$ curl -F file=@stream.js localhost:8080
------------------------------41e92562223e
Content-Disposition: form-data; name="file"; filename
Content-Type: application/octet-stream


Streams
var spawn = require('child_process').spawn;

http.createServer(function(req, res) {
var params = req.url.split('/');
var args = [params[1], '-resize', params[2], '-'];
var convert = spawn('convert', args);

convert.stdout.pipe(res);
}).listen(8080);

On Github

felixge/node-convert-example

NPM
• Puts dependencies in the right place, then
gets out of your way

• No modiﬁcation of a global load path
(require.paths is gone in 0.6.x)

• 5369+ Modules in npm, > 10 new
modules / day

So what is node good
for?

Use cases

• WebSockets/Push applications

• Proxying data streams

• Backend for single page apps

Use cases

• Spawning other programs (processes) to do
work / IPC

• Parallelizing I/O

So what is node not
good for?

Anti-Use cases
• Hard Realtime Systems

• Number crunching / huge in-memory
datasets

• (CRUD apps)

Join the Community

• Mailing list (nodejs, nodejs-dev)

• IRC (#node.js) - 700+ User online

What’s next?

• Domains

• Improved Stream API

Node.js - A practical introduction (v2)

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