Rack

Problem Every HTTP statuses code are available in form of symbol in Rails in a slightly more readable form. You may heard few of them like {% highlight ruby %} :ok :not_modified {% endhighlight %}

Rack middleware is a simply bigger thing then rails. It’s look-alike rack application that you can use to filter, process, or otherwise mess with responses.There is middleware like warden - devise, to work on catch and log exceptions, deal with cookies, SSO, and pretty much anything else you can think of.