Nodejs - A quick tour (v6)

node.js
A quick tour

Felix Geisendörfer

20.04.2011 (v6)

@felixge

Twitter / GitHub / IRC

About

• Felix Geisendörfer

• Berlin, Germany

• Debuggable Ltd

Core Contributor

&

Module Author

node-mysql node-formidable

File uploading & processing as an infrastructure
service for web & mobile applications.

Server-side JavaScript

• Netscape LiveWire (1996)

• Rhino (1997)

• 50+ plattforms since then

What was the problem?

• Slow engines

• Lack of interest in JS until ~2005

• Better competing plattforms

Why JavaScript?
3 Reasons

V8 (Chrome)

SpiderMonkey (Firefox) JavaScriptCore (Safari)

#2 - JS Engine Wars
Chakra (IE9) Carakan (Opera)

check out:
arewefastyet.com

Node's goal is to provide an easy way to build
scalable network programs.

Node.js

• Created by Ryan Dahl

• Google’s V8 JavaScript engine (no DOM)

• Module system, I/O bindings, Common Protocols

Installing

$ git clone
git://github.com/ry/node.git
$ cd node
$ ./configure
$ make install

Hello World

$ cat test.js
console.log('Hello World');

$ node test.js
Hello World

Ingredients
libeio libev

c-ares V8

http_parser

Philosophy

• Just enough core-library to do I/O

• Non-blocking

• Close to the underlaying system calls

Blocking I/O

var a = db.query('SELECT A');
console.log('result a:', a);

var b = db.query('SELECT B');
console.log('result b:', b);

Time = SUM(A, B)

Non-Blocking I/O
db.query('SELECT A', function(result) {
console.log('result a:', result);
});

db.query('SELECT B', function(result) {
console.log('result b:', result);
});

Time = MAX(A, B)

Non-Blocking I/O

• Ofﬂoad most things to the kernel and poll
for changes (select, epoll, kqueue, etc.)

• Thread pool for anything else

Single Threaded
var a = [];
function first() {
a.push(1);
a.push(2);
}

function second() {
a.push(3);
a.push(4);
}

setTimeout(first, 10);
setTimeout(second, 10);

Single Threaded
var a = [];
function first() {
a.push(1); • [1, 2, 3, 4] ?
a.push(2);
}
• [3, 4, 1, 2] ?
function second() {
a.push(3);
a.push(4); • [1, 3, 2, 4] ?
}

• BAD_ACCESS ?

Single Threaded
var a = [];
function first() {
a.push(1); • [1, 2, 3, 4]
a.push(2);
}
• [3, 4, 1, 2]
function second() {
a.push(3);
a.push(4); • [1, 3, 2, 4]
}

• BAD_ACCESS

CommonJS Modules
$ cat hello.js
exports.world = function() {
return 'Hello World';
};

$ cat main.js
var hello = require('./hello');
console.log(hello.world());

$ node main.js
Hello World

Child processes
$ cat child.js
var spawn = require('child_process').spawn;
var cmd = 'echo hello; sleep 1; echo world;';

var child = spawn('sh', ['-c', cmd]);
child.stdout.on('data', function(chunk) {
console.log(chunk.toString());
});

$ node child.js
"hellon"
# 1 sec delay
"worldnn"

Http Server
$ cat http.js
var http = require('http');
http.createServer(function(req, res) {
setTimeout(function() {
res.writeHead(200);
res.end('Thanks for waiting!');
}, 1000);
}).listen(4000);

$ curl localhost:4000
# 1 sec delay
Thanks for waiting!

Tcp Server
$ cat tcp.js
var tcp = require('tcp');
tcp.createServer(function(socket) {
socket
.on('connect', function() {
socket.write("Hi, How Are You?n> ");
})
.on('data', function(data) {
socket.write(data);
});
}).listen(4000);

$ nc localhost 4000
Hi, How Are You?
> Great!
Great!

DNS

$ cat dns.js
var dns = require('dns');
dns.resolve('nodejs.org', function(err, addresses) {
console.log(addresses);
});

$ node dns.js
[ '8.12.44.238' ]

Watch File
$ cat watch.js
var fs = require('fs');
fs.watchFile(__filename, function() {
console.log('You changed me!');
process.exit(0);
});

$ node watch.js
# edit watch.js
You changed me!

And much more

• UDP • Buffer

• Crypto • VM

• Assert • EcmaScript5
...

Suitable Applications

• Singe-page apps

• Real time

• Crawlers

More Applications

• Async chaining of unix tools

• Streaming

• File uploading

Web Frameworks

• Express.js (Sinatra clone)

• Fab.js (Mind-bending & awesome)

Socket.IO
var http = require('http');
var io = require('socket.io');

var server = http.createServer();
server.listen(80);

var socket = io.listen(server);
socket.on('connection', function(client){
client.send('hi');

client.on('message', function(){ … })
client.on('disconnect', function(){ … })
});

Server

Socket.IO

<script src="http://{node_server_url}/socket.io/socket.io.js" />
<script>
var socket = new io.Socket({node_server_url});
socket.connect();
socket.on('connect', function(){ … })
socket.on('message', function(){ … })
socket.on('disconnect', function(){ … })
</script>

Client

Socket.IO
• WebSocket

• Adobe® Flash® Socket

• AJAX long polling

• AJAX multipart streaming

• Forever Iframe

• JSONP Polling

Chooses most capable transport at runtime!

Ready for production?
• Handled over 100.000 ﬁle uploads

• Several TB of data

• No bugs, Memory usage betwen 30 - 80 MB
Our experience at Transloadit.com

Ready for production?

• 0.4.6 was released on April 13th

• 0.4.x API is stable

• Very few bugs, but YMMV

Things that suck
• Stack traces are lost at the event loop
boundary

• Utilizing multiple cores requires multiple
processes

• V8: 1.9 GB heap limit / GC can be
problematic

Benevolent Dictator For Life

Ryan Dahl

Community

• Mailing list (nodejs, nodejs-dev)

• IRC (#node.js)

More information

nodeguide.com

Meet the community
nodecamp.de

June 11 - 12

Cologne, Germany
Tickets available 12pm CET tomorrow

Questions?

✎ @felixge / felix@debuggable.com

Speed
var http = require(’http’)
var b = new Buffer(1024*1024);

http.createServer(function (req, res) {
res.writeHead(200);
res.end(b);
}).listen(8000);

by Ryan Dahl

Speed
100 concurrent clients
1 megabyte response

node 822 req/sec
nginx 708
thin 85
mongrel 4

(bigger is better)
by Ryan Dahl

Speed

• NGINX peaked at 4mb of memory

• Node peaked at 60mb

• Very special circumstances
by Ryan Dahl

What about all those
callbacks?

db.query('SELECT A', function() {
db.query('SELECT B', function() {
db.query('SELECT C', function() {
db.query('SELECT D', function() {
// ouch
});
});
});
});

Nested Callbacks

• Function does too many things, break it up

• Use an sequential abstraction library

• Consider using a JS language extension

Nested Callbacks

err1, result1 = db.query! 'SELECT A'
err2, result2 = db.query! 'SELECT B'
err3, result3 = db.query! 'SELECT C'
err4, result4 = db.query! 'SELECT D'

Kaffeeine

Nodejs - A quick tour (v6)

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