Introduction to NodeJS

What is Node JS ?
According to Node Website (nodejs.org) :
Node.js® is a JavaScript runtime built on Chrome's V8 JavaScript engine. Node.js
uses an event-driven, non-blocking I/O model that makes it lightweight and
efficient.
As an asynchronous event driven JavaScript runtime, Node is designed to build
scalable network applications

Important Points from Definition:
1)Based On Javascript
2)Non-blocking I/O
3)Event-Driven
4)Uses Chrome’s V8 Engine
5)Perfect for Build Scalable application
6)LightWeight

What is Blocking?
Code that is slow.
<?php
$x = 3;
$email = 'amol@gmail.com';
$result = mysqli_query($con,"SELECT * from users WHERE email = $email");
$otherCode = someCalculation();
?>

Handling More Requests in synchronous languages
Create more threads/processes to handle load.
1:1 ratio between thread and request.
1 2 3 4 n
Memory/Thread = 4 MB
RAM = 8 GB
Concurrent request = 2000

Callstack
function createUser(userName) {
createUserId(userName);
};
function createUserId(userName) {
saveUser(userName);
};
function saveUser(user) {
Save in Memory & return;
};
createUser('Mohit'); createUser(Mohit’)
createUserId(‘Mohit’)
saveUser(‘Mohit’)
Some Other Tasks();
Some Other Tasks’s callstack

Node’s Non Blocking Model
mysql.save('user',function(){
});
}
For Asynchronous Tasks Node uses callbacks and eventLoop.
mysql.save('user', callback);

Server Related
Modules
Server Related
Modules

Synchronous Task
Synchronous Task
Asynchronous Task
mysql.save(user,callback);
Synchronous Task
Asynchronous Task
Thread Pool
Libuv
Event QueueEvent Loop
Event 1 Event 2
Event 1 Callback
Event 2 Callback

Advantages of Event Loop Model
1)It keep main thread free from time consuming tasks.
2)Main thread is able to accept large number of requests.
3)Less memory usage and thread context switching

When to use Node.Js
1)To build Data Intensive(Query Intensive) Application.
2)Highly Scalable Application

When not to use Node.Js
Applications/tasks which blocks main thread.
Example :
1)Image Processing
2)Long running mathematical computation
for(let i = 0; i < 1000000;i++) {
someTask();
}

Scaling
Using all CPU Cores
10k rpm 10k rpm 10k rpm 10k rpm
Load Balancer

Vertical Scaling
Increase machine capacity by increase processing power and memory.
80k rpm
Load Balancer

Horizontal Scaling
Increase Application throughput by increasing number of servers.
Load Balancer Load Balancer Load Balancer
Load Balancer

NPM
NPM is package manager for NodeJS.
NPM Motto : do one thing and do it well

Http Server
const http = require('http');
const hostname = '127.0.0.1';
const port = 3000;
const server = http.createServer(function(req, res) {
setTimeout(function() {
res.end('Hello Worldn');
}, 100);
});
server.listen(port, hostname, function() {
console.log(`Server running at http://${hostname}:${port}/`);
});

Companies Using Node in production

Thank You
Uttam Aaseri
uttam.aaseri@canvass.in

Introduction to NodeJS

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