Rack is a Ruby web server interface that sits between web servers handling HTTP requests and Ruby applications. It provides a minimal interface for building web servers that cleanly separates the concerns of web service from the application logic. Rack uses middleware as hooks that process requests and responses, allowing additional functionality to be added to any Rack application. Common Ruby frameworks like Rails are built on Rack and utilize its middleware architecture.

1. @happynoff http://www.tinci.fr
What is Rack?
Ruby don't hurt me, no more

2. @happynoff http://www.tinci.fr
bit.ly/what-rack

3. @happynoff http://www.tinci.fr
A Ruby Webserver
Interface

4. @happynoff http://www.tinci.fr
Web Server
Your Ruby
Application
)!(@*#&$^%
MiNsWaN
WhOOPs
WHaTeVer

5. @happynoff http://www.tinci.fr
Web Server
Your Ruby
Application
Rack
Yup!
Here you go!
Huh, I've this
request… Do you
know what it's
about?!

6. @happynoff http://www.tinci.fr
Web Server
Your Ruby
Application
Huh, I've this
request… Do you
know what it's
about?!
Rack
Well, let me
check…

7. @happynoff http://www.tinci.fr
Web Server Rack
Hey girl, there's this
guy asking about a
request and all…
Your Ruby
Application
Of course!
Here's for you.
Have fun!

8. @happynoff http://www.tinci.fr
Web Server
Your Ruby
Application
Thanks, you're
very kind.
Rack
Ok! Here is what
I've made for
you.

9. @happynoff http://www.tinci.fr
Responses!

10. @happynoff http://www.tinci.fr
[ , , ]Status Headers Body

11. @happynoff http://www.tinci.fr
[
"200",
{ "Content-Type" => "text/html" },
["Hello world!"]
]

12. @happynoff http://www.tinci.fr
Web Server
Your Ruby
Application
Rack
HTTP GET /
…

13. @happynoff http://www.tinci.fr
Web Server
Your Ruby
Application
Rack
HTTP GET /
…

14. @happynoff http://www.tinci.fr
Web Server
Your Ruby
Application
Rack
env

15. @happynoff http://www.tinci.fr
Web Server
Your Ruby
Application
Rack
env

16. @happynoff http://www.tinci.fr
Rack
Middleware
Middleware
Middleware
Middleware
Middleware
server
app

17. @happynoff http://www.tinci.fr
Rack
Middleware
Middleware
Middleware
Middleware
Middleware
app
server

18. @happynoff http://www.tinci.fr
Middle-what?

19. @happynoff http://www.tinci.fr
class MyMiddleware
end

20. @happynoff http://www.tinci.fr
class MyMiddleware
def initialize(app)
@app = app
end
end

21. @happynoff http://www.tinci.fr
class MyMiddleware
def initialize(app)
@app = app
end
def call(env)
@app.call(env)
end
end

22. @happynoff http://www.tinci.fr
class Trollware
def initialize(app)
@app = app
end
def call(env)
status, headers, resp = @app.call(env)
["404", headers, resp.body]
end
end

23. @happynoff http://www.tinci.fr
And Rails?

24. @happynoff http://www.tinci.fr
$ rake middleware

25. @happynoff http://www.tinci.fr
use Rack::Sendfile
use ActionDispatch::Static
use Rack::Lock
use #<ActiveSupport::Cache::Strategy::…>
use Rack::Runtime
use Rack::MethodOverride
use ActionDispatch::RequestId
use Rails::Rack::Logger
use ActionDispatch::ShowExceptions
use WebConsole::Middleware
use ActionDispatch::DebugExceptions
use ActionDispatch::RemoteIp
use ActionDispatch::Reloader
use ActionDispatch::Callbacks
use ActiveRecord::Migration::CheckPending
use ActiveRecord::ConnectionAdapters::…
use ActiveRecord::QueryCache
use ActionDispatch::Cookies
use ActionDispatch::Session::CookieStore
use ActionDispatch::Flash
use ActionDispatch::ParamsParser
use Rack::Head
use Rack::ConditionalGet
use Rack::ETag
run MyApp::Application.routes

26. @happynoff http://www.tinci.fr
ActionDispatch::Static

27. @happynoff http://www.tinci.fr
ActionDispatch::ParamsParser

28. @happynoff http://www.tinci.fr
run MyApp::Application.routes

29. @happynoff http://www.tinci.fr
Resources

30. @happynoff http://www.tinci.fr
guides.rubyonrails.org/
rails_on_rack.html

31. @happynoff http://www.tinci.fr
https://github.com/rack/
rack-contrib

32. @happynoff
inci
www.tinci.fr
Simon Courtois, Software Architect at
Ruby on Rails, .NET, EmberJS

33. @happynoff http://www.tinci.fr
Questions?

34. @happynoff http://www.tinci.fr
Thanks