Node.js - A Quick Tour

node.js
A quick tour

by Felix Geisendörfer

Why?

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

How?

Keep slow operations from
blocking other operations.

Traditional I/O

var data = file.read('file.txt');
doSomethingWith(data);

Something is not right here

Traditional I/O

var data = file.read('file.txt');

// zzzZZzzz FAIL!

Don’t waste those cycles!

Async I/O

file.read('file.txt', function(data) {
}); WIN !
doSomethingElse();

No need to wait for the disk,
do something else meanwhile!

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

main.js
var hello = require('./hello');
var sys = require('sys');
sys.puts(hello.world());

$ node main.js
Hello World

Child processes
child.js
var child = process.createChildProcess('sh',
['-c', 'echo hello; sleep 1; echo world;']);
child.addListener('output', function (chunk) {
p(chunk);
});

$ node child.js
"hellon"
# 1 sec delay
"worldn"
null

Http Server
var http = require('http');
http.createServer(function(req, res) {
setTimeout(function() {
res.sendHeader(200, {'Content-Type': 'text/plain'});
res.sendBody('Thanks for waiting!');
res.finish();
}, 1000);
}).listen(4000);

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

Tcp Server
var tcp = require('tcp');
tcp.createServer(function(socket) {
socket.addListener('connect', function() {
socket.send("Hi, How Are You?n> ");
});
socket.addListener('receive', function(data) {
socket.send(data);
});
}).listen(4000);

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

DNS
dns.js
var dns = require('dns');
dns.resolve4('nodejs.org')
.addCallback(function(r) {
p(r);
});

$ node dns.js
[
"97.107.132.72"
]

Watch File
watch.js
process.watchFile(__filename, function() {
puts('You changed me!');
process.exit();
});

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

ECMAScript 5
• Getters / setters
var a = {};
a.__defineGetter__('foo', function() {
return 'bar';
});
puts(a.foo);

• Array: ﬁlter, forEach, reduce, etc.

• JSON.stringify(), JSON.parse()

There is only 1 thread
file.read('file.txt', function(data) {
// Will never fire
});

while (true) {
// this blocks the entire process
}

Good for conceptual simplicity
Bad for CPU-bound algorithms

Web workers
• Multiple node processes that do
interprocess communication

• CPU-bound algorithms can run separately

• Multiple CPU cores can be used efﬁciently

Move C/C++ stuff to JS

• Simpliﬁes the code base

• Makes contributions easier

• Low-level bindings = more ﬂexibility

Better Socket Support
• Support for unix sockets, socketpair(), pipe()

• Pass sockets between processes " load
balance requests between web workers

• Uniﬁed socket streaming interfaces

Even more ...
• Connecting streams
var f = file.writeStream('/tmp/x.txt');
connect(req.body, f);

• Http parser bindings

• No memcpy() for http requests
+ hot code reloading!

Suitable Applications

• Web frameworks

• Real time

• Crawlers

More Applications

• Process monitoring

• File uploading

• Streaming

Http Chat in 14 LoC
var
http = require('http'),
messages = [];

http.createServer(function(req, res) {
res.sendHeader(200, {'Content-Type' : 'text/plain'});
if (req.url == '/') {
res.sendBody(messages.join("n"));
} else if (req.url !== '/favicon.ico') {
messages.push(decodeURIComponent(req.url.substr(1)));
res.sendBody('ok!');
}
res.finish();
}).listen(4000);

The chat room:

http://debuggable.com:4000/

Send a message:

http://debuggable.com:4000/<msg>

Questions?

✎ @felixge
$ http://debuggable.com/

Dirty

NoSQL for the little man!

Dirty

JavaScript Views Memory Store
Disk Persistence Speed > Safety

Dirty

Dirty Hello World
hello.js
var
Dirty = require('../lib/dirty').Dirty,
posts = new Dirty('test.dirty');

posts.add({hello: 'dirty world!'});
posts.set('my-key', {looks: 'nice'});

$ node hello.js
$ cat test.dirty
{"hello":"dirty world!","_key":"3b8f86..."}
{"looks":"nice","_key":"my-key"}

Reloading from Disk
hello.js
var

posts.load()
.addCallback(function() {
p(posts.get('my-key'));
});

$ node hello.js
{"looks": "nice", "_key": "my-key"}

Filtering records
hello.js
var

posts.load()
.addCallback(function() {
var docs = posts.filter(function(doc) {
return ('hello' in doc);
});
p(docs);
});

$ node hello.js
[{"hello": "dirty world!", "_key": "3b8f86..."}]

My Results

• Set: 100k docs / sec

• Iterate: 33 million docs / sec

• Filter: 14 million docs / sec
(on my laptop - your milage may vary)

Use Cases

• Small projects (db < memory)

• Rapid prototyping

• Add HTTP/TCP interface and scale

http://github.com/felixge/node-dirty

(or google for “dirty felixge”)

Node.js - A Quick Tour

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