An introduction to Node.js application development

Introduction to Node.js application
development
Dr. Jayaraj Poroor
Founder & CEO, Shelloid
http://shelloid.com http://shelloid.org
GTech TFG, Jan 21 2015

About Shelloid
Open Source Technology (http://shelloid.org)
Operational Log Intelligence (http://shelloid.com)

Server-side technology requirements
● Performance
o Need optimized execution
● Concurrency
o Need to support many concurrent client requests
● Library support
o e.g., database interfacing.
● Framework support
o For rapid application development.

Node.JS
● Performance
o Google’s V8 VM with native JIT compilation
● Concurrency
o Asynchronous I/O (libuv) + clustering
● Library support
o 39K projects in Github
● Framework support
o e.g., Express.JS

Synchronous vs Asynchronous I/O
● Synchronous I/O
o Thread blocks till I/O request is complete.
o e.g., $result = mysql_query(“....”); //PHP
● Asynchronous I/O
o Thread does not block
o Uses callback mechanism to notify completion
o e.g., conn.query(“...”, function(err, rows) { }
);

Node.JS Threading model
1. Single computational thread
o Non-blocking, interleaved request processing
o Background worker threads for I/O processing
2. Clustering to utilize multi-core machines
3. No shared memory between cluster
processes.

Node.JS : When to use
● Great for
o I/O-centric applications
 e.g., DB queries, File I/O , network I/O,
invocation of other web services.
o Real-time communication
 WebSockets, HTTP long polling
● Not so great for
o Compute-centric applications
 e.g., High-end machine learning backend

Event Loop Illustrated
http://www.geekgirl.io/understanding-the-event-loop-in-nodejs/

Anatomy of a “hello world” Node.js
var http = require('http');
var server =
http.createServer(function (req, res) {
res.writeHead(200,
{'Content-Type': 'text/html'});
res.end('<h1>Hello World</h1>');
});
server.listen(3000);
No separate HTTP
engine like Apache
required.
Command:
node app.js

Serving a file
Code source: https://github.com/substack/stream-handbook
Buffers the entire file in memory.
● Inefficient for large files.
● Client needs to wait till entire file
is read.

Node.js Streams
● Data served in chunks.
● Data event fires whenever a new
chunk is ready.
Code source: Node.js in Action

Streams can be piped!
File stream (input) is piped to the
response stream (output).
The response will employ chunked
Transfer-Encoding.
Code source: https://github.com/substack/stream-handbook

Package management
● npm (Node Package Manager)
o Provides simple & powerful package management.
o Reads module dependencies from package.json
o Typical usage: npm install or npm update.
o Can store all dependent modules locally or globally

A sample package.json
{
"name": "SomeApp",
"description": "SomeApp Web Application",
"version": "0.0.1",
"private": true,
"dependencies": {
"express": "3.6.0",
"connect": "2.15.0",
"mysql": "*",
}
}

Secure HTTP with Node.js
Code source: Node.js in Action
Key and certificate files provided.
Use gpg, openssl etc. to generate key
and CSR.

Connect framework: Modular web apps
Install:
npm install connect

Connect: usage Create a Connect ‘app’.
● Will store all middleware.
● Itself just a function.
Create a middleware ‘stack’.
Requests will execute middleware
functions till ‘next()’ is not called
or end of stack is reached.
Code source: https://www.npmjs.org/package/connect

Connect: usage (2)
● Middleware can be mounted
on specific URL endpoints.
● Does basic routing.
● Error handler middleware.
Create Connect-enabled server.
Code source: https://www.npmjs.org/package/connect
OR

Serving static files Static middleware
configured with the
folder from which
files are served.

Express: Lightweight web framework
Code Source: https://www.npmjs.org/package/express
Routing

Bootstrapping Express application
express -e
output

Rendering views with Express
Express configured
with the views folder.
View engine set as
ejs.
Looks up index.ejs in
the views folder.

View lookup
Source: Node.js in Action

Passing data to views
Data passed to the
view.
photos is an array.

An example view
photos array
accessed here.
title variable
accessed.

Database connectivity
npm install mysql
var mysql = require('mysql');
var connection = mysql.createConnection({
host : 'localhost',
user : 'me',
password : 'secret'
});
connection.connect();
connection.query('...', function(err, rows, fields) {
if (err) throw err;
connection.end();
}); https://github.com/felixge/node-mysql
npms available for virtually
any SQL/NoSQL
database!
Query completes
only when the
callback is invoked!

Authentication
● passport.js
o Authentication middleware for node.js.
o 140+ authentication strategies.
o Supports OpenID and OAuth
o http://passportjs.org
o Session data can be serialized into a store like
Redis.
npm install passport

Read more
● Node.js in Action
● http://expressjs.com
● http://www.nodebeginner.org/

Using Shelloid
npm install -g shelloid
shelloid app-folder [env name]
Learn more at http://shelloid.org
Requires
admin/super user
privilege

Dr. Jayaraj Poroor
Founder, Shelloid Systems
Open source cloud-ready Node.js application server
jayaraj@shelloid.com
http://shelloid.com
Thank You

An introduction to Node.js application development

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