Rails 4 in Action

Chapter 15. Rack-based applications

This chapter covers

• Learning how HTTP requests work under the hood with Rack
• Mounting Rack applications inside a Rails application
• Introduction to the Sinatra web framework
• Intercepting requests with custom middleware

So far, this book has primarily focused on how to work with pieces of the Rails framework. In this chapter, we’ll look at something lower-level than that: the Rack web server interface.

Rack is the underlying web server framework that powers the request/response cycle found in Rails, but it isn’t a part of Rails itself. It’s completely separate, with Rails requiring the parts of Rack it needs. When your application runs, it’s run through a web server. When your web server receives a request, ...