Exploring Node.jS

Exploring Node.JS
Dr. Jayaraj Poroor
DependSoft Consulting
http://dependsoft.com

My ongoing R&D work: IntegralJ
http://integralj.org (open source)

My recent products
● Virtual Private Transport
o Keyhole approach to secure remote service access.
o http://shelloid.com
o Node.js, Netty, Redis, MySQL, Google protobuf.
o Basic engine open sourced.
● Sensoid IoT platform
o Distributed stream query platform.
o Node.js, Redis, InfluxDB, ElasticSearch, MySQL.

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
1. Clustering to utilize multi-core machines
2. 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
Buffers the entire file in memory.
●Inefficient for large files.
●Client needs to wait till entire file is
read.
Code source: https://github.com/substack/stream-handbook

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
Source: Node.js in Action
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.
OR
Create Connect-enabled
server.
Code source: https://www.npmjs.org/package/connect

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

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

Bootstrapping Express application
express – e output

Rendering views with Express
Code Source: Node.js in Action
Express configured
with the views
folder.
View engine set as
ejs.
Looks up index.ejs
in the views folder.

View lookup

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

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

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
npm install passport
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.

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

Thank You
Dr. Jayaraj Poroor
Founder, DependSoft Consulting
Peace of mind with dependable software.
jayaraj@dependsoft.com
http://dependsoft.com

Exploring Node.jS

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