Rails%203%20In%20Action

This chapter covers
� Building a basic Rack application
� Tying together Rack applications
� Mounting a Rack app within a Rails app
Rack-based applications
� Using Rack middleware to alter server response
So far, this book has primarily focused on how to work with pieces of the Rails
framework, such as application and engines. In this chapter, we’ll look at how you
can use Rack-based applications to respond more quickly than what you’d otherwise
be capable of with your main application.
Rack is the underlying web server framework that powers the underlying
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
is running, it’s running through a web server. When your web server receives a
request, it will pass it off to Rack, as shown in figure 18.1.
Rack then determines where to route this request, and in this case it has chosen
to route to a specific application stack. The request passes through a series of
pieces called middleware (covered in the final section of this chapter) before arriving
at the application itself. The application will then generate a response and pass
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