real timeninja - codemotion 2015 roma

Real Time NinjaHands On MEAN

Giovanni Lela

CTO @ LinkMe

Cofounder @ MeanMilan

Matteo Scandolo

MEAN Dev @ LinkMe

Cofounder @ MeanMilan

What's nextWhen / why did it start

Extremely boring theory

What to do aka common use cases

Differences from client side javascript

App example: a RESTful ninja managament tools

with real time notifications

Pre - nodejs1994 - Netscape enterprise server

1996 - Microsoft Internet Information service

Enter node jsIn 200* Ryan Dahl saw a polling progress bar

He wanted a super easy way to implement sites with pushcapabilities

In 2009 node.js was born

Joyent takes control

Hype and dissatisfactionIn the following years node.js gains substantial traction

In 2014, community dissatisfaciton lead to io.jsWhat now?

Why should I care?It can can handle a lot of concurrent I/O operations

Because of non blocking I/O and javascript's own nature

Blocking I/O analogyEach cashier (thread) server one

customer at a time

Blocking I/O analogy (2)The cashier waits for your food

to be cooked before doinganything else (he’s blocked)

The cashier is not able to help thenext person until you got your

food and went your way

Blocking I/O analogy (3)The more customers you want to serve at once the more cashier

lines you need

Cashier lines -> thread

Multi-threaded parellel execution

Non-blocking I/O analogyAs soon as you place your order, it’s sent off for someone to fulfill

while the cashier is still taking your payment.

When you are done paying, you have to step aside because thecashier is already looking to service the next customer.

When your food is set, the cashier – or someone – will signal you bycalling out your name, (callback)

Non-blocking I/O (2)You use your web browser to make a request for “/about.html” on

a Node.js web server.

The Node server accepts your request and calls a function toretrieve that file from disk.

While the Node server is waiting for the file to be retrieved, itservices the next web request.

When the file is retrieved, there is a callback function that isinserted in the Node servers queue.

The Node server executes that function which in this case wouldrender the “/about.html” page and send it back to your web browser.

So:Every I/O operation is non blocking

Your code is single threaded

Everything runs in parallel except your code

"Everything runs in parellelexcept your code"

http://slides.com/adamterlson/promises#/

Event loopA JavaScript runtime contains an event queue, which is a list of

tasks to be processed

Each message event is bound to a callback function

The said runtime loops on the queue, executing all the event callbacks

Event loopwhile(queue.waitForMessage()){  queue.processNextMessage();}

Event loop as a languageIn javascript the event loop is not a library it's a language construct

Event loop in ruby /eventmachine

require 'eventmachine'

module Echo def post_init  puts "Connection Connected Yo" end def receive_data  send_data "#{data}"  close_connection if data =~ /quit/if endend

EventMachine.run {  EventMachine.start_server "127.0.0.1", 8081, Echo}

Event loop in node.js (and es6!)require('net').createServer((socket)=>{

 console.log('Connection connected'); socket.on('data', req => socket.write(req.toString()))}).listen(8000);

What not to doeverything that is CPU intensive

image/video processing

heavyweight number crunching

compressing files

everything involving complex algorithms

Event loops are highly specialized and not general purpose

"Everything runs in parellelexcept your code"

http://slides.com/adamterlson/promises#/

What to do - APIsREST/JSON Api

Plays well with non relational db

LOTS of stable and mature frameworks: hapi, restify, express,loopback

What to do - Fullstack appsGood ol’ MEAN stack

Isomorphic applications:

Shared models

Shared rendering

What to do - Real time webapps

It was born for this

Lots of stable mature frameworks (again) - primus, socket I/O ecc

It ca ben integrated into an existing web stack

http://webandphp.com/IntegratingNode.jswithPHP

Other interesting fields ofapplication

Desktop Apps

Microservices

Embedded

Differences from the front endNo DOM api

No browser APIs globals: window, document

No browser inconsistencies: you just get the V8

Excellent parts of javascriptsArray.prototype.forEach(), Array.prototype.map(), Object.keys() [...]

http://kangax.github.io/compat-table/es5/

http://kangax.github.io/compat-table/es6/

Different globalsprocess

__filename

__dirname

CommonJS globals

global

Common js globals//hello.js exports.getGreetings = function() {   return 'Hello World'; };

//example.jsvar hello = require('./hello.js');var greetings = hello.getGreetings();

Built in librariesfs

net

stream

Many, many callbackscan lead to really confused code

many tools to manage this

some FP is necessary

And now?Let's Code!

What are we going to do?Setup the environment

Connect to MongoDB

Define "Models"

Define Routes and Middlewares

Implement a basic CRUD

A basic FrontEnd

And finally... Realtime!

Try it on

ninja.link-me.it

Thanks for listening

Keep in touch

Giovanni Lela: @lambrojos

Matteo Scandolo: @_teone

LinkMe: @LinkMeSRL -

@MM_MeanMilan -

www.link-me.it

github.com/MeanMilan