Rack Middleware Exercise

This is a simple exercise to learn about writing Rack apps and middleware. The goal is write four pieces of middleware that pass the test suite provided.

The middleware in brief:

• Rescue and handle exceptions
• Authorize requests via API token
• Censor sensitive information
• Handle JSONP formatted requests

The exercise will provide you with an existing environment, so you only need to worry about implementing the middleware. This repo includes tests to guide your development.

This is part of the YYC Ruby February 2015 meetup about Rack and Middleware. Slides from the talk are available on SpeakerDeck.

Getting Started

Clone the repo:

git clone git@github.com:yycruby/middleware_exercise.git

Install necessary gems:

bundle install

Run the tests:

rake test

If you want to share your solutions, you can fork the repo and open a pull request!

Middleware Exercises

There are four pieces of middleware to implement. Here is a brief description of what each middleware does.

Authorize

lib/authorize.rb

Performs basic authorization by token, which is used to find a user and then set the current user in the env. A user repository instance is passed into the middleware when it is initialized. If a user is not found, it responds with 401 Unauthorized status.

use Authorize, UserRepo
run MyApp.new

LogErrors

lib/log_errors.rb

A basic exception handler. When an exception is raised, this rescues it, logs the source of the error and returns an appropriate 500 Internal Server Error status.

use LogErrors
run MyApp.new

Censored

lib/censored.rb

More of a fun middleware to demonstrate something that modifies the response from a downstream app. A black list of words is passed to the initializer and it then replaces any instances of a word with REDACTED. The Content-Length of the response is also updated to reflect the changes.

use Censored, ['Area 51', 'Roswell', 'Alien Pilot']
run MyApp.new

JsonP

lib/jsonp.rb

Simple, but naive JSONP wrapper. When a request includes a callback parameter and the response is application/json, it wraps the response in a JavaScript callback and updates the response Content-Length.

use JsonP
run MyApp.new

Solutions

If are interested in seeing implementations for these tests, you can check out the solution branch. All of the tests were implemented against these, so the tests are real.

git checkout solution