Simple Introduction to Real-time systems and specially using Node.js in that - at #CATscope13 SAT 27/4/2013

1. REAL-TIME WEB
Medhat Dawoud
www.medhatdawoud.net
@Med7atDawoud

3. What is Real-time web
• The meaning is that: users can see the contents
as fast as the author publish it (like chat
applications)
• A lot of technologies are used to implement the
Real-time systems.
• Today I’m interested in a technology that do that
for us in an easy, reliable, and fantastic way

4. To create Real-time system on web we need ..
• Very fast web server.
• Very very fast I/O operations (Non-blocking).
• System that depend on event-driven(event-loops).
• Flexible tool to handle all of this in a simple way.

5. Some technologies for Real-time systems
Python [ twisted ]
Ruby [ EventMachine ]
Perl [ AnyEvent ]
If you deal with one of them, this presentation will be really understood at once.

6. Finally , The Magic Technology Appears
• 2009 - this guy “Ryan Dahl” releases something
that support the highly-performance
concurrent applications.
• It’s called Node.js

7. What is Node.js ?
• In simple words Node.js is ‘server-side JavaScript’.
• In not-so-simple words Node.js is a high-performance
network applications framework, well optimized for high
concurrent environments.
• It’s Open Source. It runs well on Linux systems, can
also run on Windows systems.
• uses an asynchronous event-driven model.

8. What is Node.js ?
• Built and run on V8 JavaScript engine.
• In ‘Node.js’ , ‘.js’ doesn’t mean that its solely written
JavaScript. It is 40% JS and 60% C++.
• is now the most followed project on Github,
exceeding Ruby on Rails .. woooooo
• From the official site:
‘Node's goal is to provide an easy way to build scalable
network programs’ - (from nodejs.org!)

9. Google V8 engine
• V8 is an open source JavaScript engine
developed by Google. It’s written in C++ and is
used in Google Chrome Browser.
• Faster than SpiderMonkey (used in firefox) over
4 times ( when V8 was invented ) 
- from an expert on stakoverflow -

11. Theory 1 : Event-loops
Event-loops are the core of event-driven programming, almost
all the UI programs use event-loops to track the user event, for
example: Clicks, Ajax Requests etc.
Client
Event loop
(main thread)
C++ Threadpool
(worker threads)
Clients send HTTP requests
to Node.js server
An Event-loop is woken up by OS,
passes request and response objects
to the thread-pool
Long-running jobs run
on worker threads
Response is sent
back to main thread
via callback
Event loop returns
result to client

12. Theory 2 : Non-blocking I/O
• Traditional I/O
var result = db.query(“select x from table_Y”);
doSomethingWith(result); //wait for result!
doSomethingWithOutResult(); //execution is blocked!
• Non-traditional, Non-blocking I/O
db.query(“select x from table_Y”,function (result){
doSomethingWith(result); //wait for result!
});
doSomethingWithOutResult(); //executes without any delay!

13. Natural & Features of Node.js ( some confusing )
• Apply it in the coolest, sexiest, most popular
language on the planet.
• Node.js uses an event-driven, non-blocking I/O
model, which makes it lightweight.
• The big support of V8 from Google is a great power.

14. Why JavaScript was suitable for that ?
• JavaScript Callbacks feature that solve the problem of
event-loops.
• The great NPM (Node Package Manager).
• Node.js JavaScript quite different : there is no DOM
implementation provided by Node.js,
• i.e. you can not do this:
var element = document.getElementById(“elementId”);
• Everything inside Node.js runs in a single-thread.
Natural & Features of Node.js ( some confusing )

15. What can we do with Node.js
• You can create an HTTP server and print ‘hello world’
on the browser in just 4 lines of JavaScript.
• You can create a DNS server.
• You can create a Web Chat Application like GTalk in the
browser.
• Node.js can also be used for creating online games,
collaboration tools or anything which sends updates to
the user in Real-time.

16. Example: Creating Http server

17. When to use Node.js ?
• streaming based Real-time services, online
games, web chat applications,..etc.
• If you need high level concurrency and not
worried about CPU-cycles.
• If you are good at JavaScript code.
• You will develop the front-end and back-end in the same
language, what a triumph 

18. Some Benchmarks (proof of power)
Taken from:
http://code.google.com/p/node-js-vs-apache-
php-benchmark/wiki/Tests
A benchmark between Apache+PHP
and node.js, shows the response time
for 1000 concurrent connections
making 10,000 requests each, for 5
tests.

19. Some Benchmarks (proof of power)
Taken from:
http://nodejs.org/jsconf2010.pdf
The benchmark shows the
response time in milli-secs for 4
evented servers.

20. Who is using Node.js
Complete list can be found at: https://github.com/joyent/node/wiki/Projects,-Applications,-and-Companies-Using-Node

21. Some Modules you will love them
• Express– to make things simpler e.g. syntax, DB connections.
• Jade – HTML template system
• Socket.IO– to create real-time apps
• CoffeeScript – for easier JavaScript development
Find out more about some widely used Node.js modules at:
http://blog.nodejitsu.com/top-node-module-creators

22. The last thing to say (How to start ?!)
• Try to explore the rest of Node.js your self.
• I recommend a free book to start called
• ( O’raily Book : Up and Running With Node.js)
• Tutorial sites:
• Nodejs.org
• Letsnode.com
• Google.com
• The series of articles in arabic isA on ( medhatdawoud.net)

23. Medhat Dawoud
www.medhatdawoud.net
Twitter: @Med7atdawoud
Thanks