The document discusses Rack middleware and how it can be used to enrich Rack applications. It covers what Rack and middleware are, provides examples of middleware for redirection, rate limiting and calling third party services, and how middleware can be used within both Rack apps and Rails apps. It also discusses some best practices for middleware including only using what is needed, ordering, and designing middleware for single purposes.

1. Rack middlewares
The Ins & Outs
By: Ahmed Shahin

2. ● What is Rack? Why?
● Sample Rack application
● What is Middleware?
● Enrich our Rack app with middlewares
● Use middlewares within a Rails app
● Watch-outs
Agenda

3. What is Rack?

4. What Is Rack?

5. What Is Rack?

6. What is Rack App?

7. ● Any object that responds to a ‘call’ method
● Accepts ‘env’ parameter
● Returns a 3-elements array:
○ Status code #Integer
○ Headers # Hash
○ Body # Enumerable

8. Sample Rack App

10. Using middlewares
Let’s add some features!
● Redirection for obsolete pages
● Rate limiting
● Send every request url to a third party service.

11. What is Middleware?

12. Same as Rack App:
Also, constructor that takes ‘app’ argument

13. Middleware: Redirection for obsolete pages

15. Middleware: Rate limiting

17. Middleware: Call a third party service

19. Use them in the Rack app

21. Also, you can use them in a Rails app

23. And see them in action

25. Watch-outs

26. Performance

28. A solution: Use it when you actually need it

29. From “Warden” documentation
“Warden is designed to be lazy. That is, if you don't use it,
it doesn't do anything..”

30. Ordering

32. Single purpose

34. Conclusion
Middlewares are very powerful, Just be gentle with it!

35. Thank you!
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