Intro to node.js - Ran Mizrahi (27/8/2014)

Introduction to
{ node.js }
Ran Mizrahi (@ranm8)
Founder and CEO, CoCycles

About { Me }
• Founder and CEO of CoCycles.
• Former Open Source Dpt. Leader of CodeOasis.
• Architected and lead the development of the Wix App Market.
• Full-stack and hands-on software engineer.

What is { node.js }
• Server-side JavaScript development platform.
!
• Built on top of Chrome’s JavaScript runtime engine V8.
!
• Aims for easy development of scalable, non-blocking I/O, real
time and network applications.
!
• Written in C/C++ and JavaScript.
!
• CommonJS module system.
!
• node.js is single-threaded and uses event-loop.
!
!

What is { V8 }
• V8 is Google Chrome's JavaScript runtime engine.
!
• Implements ECMAScript specification (5th edition).
!
• Standalone and can be embedded to any C++ application.
!
• Compiles JavaScript to native machine code before executing it
instead of interpreting.
!
• Open sourced under the new BSD license.
!
!

{ Thread per Connection } Burgers Restaurant

Something is { WRONG }, we
must
do it { BETTER }!!!

Event-Driven { Burgers Restaurant }

{ Apache } vs. { NGINX } vs Performance
Requests per second:

Memory usage:

So, what is the big difference between Apache and Nginx?
• Apache uses one thread per connection.
• Hard to scale.
• Resource expensive.
!
• NGINX is single-threaded and uses event-loop for handling
requests.
• Easy to scale.
• Lower resources consumption.

{ Blocking } I/O
What is the software doing while it queries to the DB?!?
var response = db.query('select * form users');
// use the result
In most cases, nothing (/:
• Better software should handle I/O differently! It should
multitask.
!
• Other tasks should be performed while waiting..
!
!
!

{ Non-Blocking } I/O
Non-blocking code:
db.query('select * form users', function(result){
This is how I/O should be handled in concurrency, when the
DB will respond, the given function will be executed.
!
!
// Use the result
});
!
console.log(logSomething);

So Why Everyone Aren’t Using { Non-Blocking I/O }
This what we learn:
puts('Enter you name:');
var name = gets();
puts('Hello ' + name);
Considered too complicated (:/
puts('Enter you name here:');
gets(function(name) {
puts('Hello ' + name);
});

But Why { JavaScript } ?
JavaScript is designed specifically to be used with an event-loop:
!
• Anonymous functions, closures.
!
• Executes one callback at a time.
!
• Tested over years with I/O through DOM event callbacks.
!
• Web developers already know JavaScript (decreases the
learning curve dramatically).

The { node.js } Project
• Provides purely event-driven, non-blocking infrastructure to
write high concurrency applications.
!
• Uses JavaScript for easy development of asynchronies apps.
!
• Open source and extendable module system.
https://github.com/popular/starred

Hello { JavaScript Israel }
setTimeout(function() {
console.log(‘JavaScript Israel!');
}, 2000);
!
console.log('Hello');
• The program outputs “Hello”, then waits two seconds and
outputs “JavaScript Israel!”.
!
• While waiting for the timeout to complete, node.js will keep
performing other tasks.
• Node exits automatically when nothing is left to do.

Streaming { HTTP Server }
var http = require('http');
!
var server = http.createServer(function(request, response) {
response.writeHead(200, { 'Content-Type': 'text/plain' });
!
response.end(‘JavaScript Israel!n');
}, 2000);
!
response.write('Hellon');
});
!
server.listen(8000);
Let’s benchmark that... and see the results..
20 secs, with single thread is the result of non-blocking structure.

DNS { Resolver }
var dns = require('dns');
!
console.log('resolving google.com...');
!
dns.resolve('google.com', function(error, addresses) {
if (error) throw error;
console.log('found: ' + addresses.join(', '));
});
Resolves “google.com” and outputs the result.

Common { Frameworks and
Tools }

NPM { Node Package Manager }
npm usage:
Installs package in the current local directory:
$ npm install express
Installs package globally
$ npm install express -g

{ Express }
Express is a minimal and flexible node.js web framework,
providing robust set of features for building web applications.
Taken from http://expressjs.com
Some of express features:
• Robust routing.
!
• HTTP helpers (caching, redirection, etc.)
!
• Focuses on high performance.
!
• Simplified API for working in request/response environment.
• Large community support.
!
!
!

{ Express }
Web Server example:
var express = require(‘express’),
app = express();
!
app.get(‘/api/me', function(request, response) {
// Return JSON encoded response
response.json(200,{
code: 200,
message: 'OK',
payload: null
});
});
• Creates new express HTTP server with route for path GET
“/api/me”.
!
• Returns JSON formatted response.

{ Socket.IO (1.0) } By Automattic
Socket.IO aims to make real-time apps possible in every browser
and mobile device, blurring the differences between transport
mechanisms.
Taken from http://socket.io
Some of socket.io main features:
• Runs on top of Engine.IO as cross-browser/device bi-directional
communication layer (XHR-polling, long-polling,
WebSockets, Flash, etc.).
!
• Binary Support.
!
• Disconnections detection through heartbeats.
!
• Reconnection support with buffering.
!
!

{ Socket.IO } Notifications Example
Server:
var io = require('socket.io')(server);
!
io.on('connection', function(socket) {
var notification = { body: 'Hello Exelate!' };
socket.emit('notification', notification, function(response) {
console.log(response);
});
});
Client:
var socket = io('http://localhost');
socket.on('notification', function(data, callback) {
console.log(data.body);
callback('Hello to you too!');
});

{ Mongoose }
Mongoose aims to provide elegant MongoDB object modeling
(ODM) for node.js.
Some of mongoose main features:
• Allows creating DB schemas.
!
• Virtuals, Getters and Setters.
!
• Easy validation of DB objects.
!
• Extend easily!
!
!
!

{ Mongoose }
Mongoose cat document example:
var mongoose = require('mongoose');
mongoose.connect('localhost', ‘my-db');
!
var CatSchema = mongoose.Schema({
name: {
type: String,
required: true,
default: 'My cat'
}
});
!
var Cat = mongoose.model('Cat', CatSchema);
!
var kitty = new Cat({ name: 'Kati' });
kitty.save(function(err) {
if (err) throw err;
console.log('Saved!')
});

{ TDD/BDD } using Mocha and Expect.js
Mocha
Mocha is a feature-rich JavaScript test frameworks running on
node and the browser, making asynchronies tests easy.
Main features:
• Supports both TDD and BDD styles.
!
• Both browser and node support.
!
• Proper exit status for CI support.
!
• Really easy async tests.
!
• node.js debugger support.
!
• Highly flexible, choose and join the pieces yourself (spy library,
assertion library, etc.).

{ TDD/BDD } using Mocha and Chai
Chai
Chai is a BDD/TDD assertion library for node and the browser
that can be easily paired with any JavaScript testing framework.
Main features:
• BDD style.
!
• Compatible with all test frameworks.
!
• Both node.js and browser compatible.
!
• Standalone assertion library.
• Extend easily!

{ TDD/BDD } using Mocha and Chai
“Normal” test:
var expect = require(‘chai').expect;
!
describe('Array', function() {
describe('#indexOf()', function() {
it('Expect -1 when the value is not present', function() {
var array = [1, 2, 3];
expect(array.indexOf(4)).to.be(-1);
});
});
});
Run it..
$ mocha --reporter spec
Array
#indexOf()
✓ Expect -1 when the value is not present
!
!
1 test complete (5 ms)

{ TDD/BDD } using Mocha and Expect.js
“Async” test:
var expect = require(‘chai').expect;
!
function asyncCall(val ,callback) {
var prefix = ' - ';
!
var newString = val + prefix + 'OK';
!
callback(newString);
}, 500);
}
!
describe('asyncCall', function() {
it('Add suffix that prefixed with - to the given string', function(done) {
var testVal = 'Foo';
!
asyncCall(testVal, function(response) {
expect(response).to.contain(testVal + ' - OK');
done();
});
});
});
Let’s run it...

{ Use Cases }
FXP.co.il
• Real-time notifications, forum threads and posts.
!
• 30,000 concurrency connections!
!
• We started with version 0.4 )-:..
!
• Today, runs on one web server for serving all those concurrent
connections..
!
My Contributions…
!
• Requestify - Simplified HTTP
• winston-newrelic - Winston transporter for New Relic
!
!

Intro to node.js - Ran Mizrahi (27/8/2014)

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