This are the slides for "RealTime Ninja - Hands on MEAN" talk we run in Codemotion 2015 Roma

1. Real Time Ninja
Hands On MEAN
Giovanni Lela
CTO @ LinkMe
Cofounder @ MeanMilan
Matteo Scandolo
MEAN Dev @ LinkMe
Cofounder @ MeanMilan

2. What's next
When / 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

3. Pre - nodejs
1994 - Netscape enterprise server
1996 - Microsoft Internet Information service

4. Enter node js
In 200* Ryan Dahl saw a polling progress bar
He wanted a super easy way to implement sites with push
capabilities
In 2009 node.js was born
Joyent takes control

5. Hype and dissatisfaction
In the following years node.js gains substantial traction
In 2014, community dissatisfaciton lead to io.js
What now?

6. 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

7. Blocking I/O analogy
Each cashier (thread) server one
customer at a time

8. Blocking I/O analogy (2)
The cashier waits for your food
to be cooked before doing
anything else (he’s blocked)
The cashier is not able to help the
next person until you got your
food and went your way

9. 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

10. Non-blocking I/O analogy
As 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 the
cashier is already looking to service the next customer.
When your food is set, the cashier – or someone – will signal you by
calling out your name, (callback)

11. 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 to
retrieve that file from disk.
While the Node server is waiting for the file to be retrieved, it
services the next web request.
When the file is retrieved, there is a callback function that is
inserted in the Node servers queue.
The Node server executes that function which in this case would
render the “/about.html” page and send it back to your web browser.

12. So:
Every I/O operation is non blocking
Your code is single threaded
Everything runs in parallel except your code

13. "Everything runs in parellel
except your code"
http://slides.com/adamterlson/promises#/

14. Event loop
A 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

15. Event loop
while(queue.waitForMessage()){
queue.processNextMessage();
}

16. Event loop as a language
In javascript the event loop is not a library it's a language construct

17. 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
end
end
EventMachine.run {
EventMachine.start_server "127.0.0.1", 8081, Echo
}

18. 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);

19. What not to do
everything 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

20. "Everything runs in parellel
except your code"
http://slides.com/adamterlson/promises#/

21. What to do - APIs
REST/JSON Api
Plays well with non relational db
LOTS of stable and mature frameworks: hapi, restify, express,
loopback

22. What to do - Fullstack apps
Good ol’ MEAN stack
Isomorphic applications:
Shared models
Shared rendering

23. What to do - Real time web
apps
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

24. Other interesting fields of
application
Desktop Apps
Microservices
Embedded

25. Differences from the front end
No DOM api
No browser APIs globals: window, document
No browser inconsistencies: you just get the V8

26. Excellent parts of javascripts
Array.prototype.forEach(), Array.prototype.map(), Object.keys() [...]
http://kangax.github.io/compat-table/es5/
http://kangax.github.io/compat-table/es6/

27. Different globals
process
__filename
__dirname
CommonJS globals
global

28. Common js globals
//hello.js
exports.getGreetings = function() {
return 'Hello World';
};
//example.js
var hello = require('./hello.js');
var greetings = hello.getGreetings();

29. Built in libraries
fs
net
stream

30. Many, many callbacks
can lead to really confused code
many tools to manage this
some FP is necessary

31. And now?
Let's Code!

32. 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!

33. Try it on
ninja.link-me.it

34. Thanks for listening
Keep in touch
Giovanni Lela: @lambrojos
Matteo Scandolo: @_teone
LinkMe: @LinkMeSRL -
@MM_MeanMilan -
www.link-me.it
github.com/MeanMilan