gistfile1.rb

require 'rubygems'
require 'rack'
require 'redis'

class ApiThrottling
  def initialize(app, options={})
    @app = app
    @options = {:requests_per_hour => 60}.merge(options)
  end

  def call(env, options={})
    auth = Rack::Auth::Basic::Request.new(env)
    if auth.provided?
      return bad_request unless auth.basic?
		  begin
		    r = Redis.new
		    key = "#{auth.username}_#{Time.now.strftime("%Y-%m-%d-%H")}"
		    r.incr(key)
		    return over_rate_limit if r[key].to_i > @options[:requests_per_hour]
		  rescue Errno::ECONNREFUSED
		    # If Redis-server is not running, instead of throwing an error, we simply do not throttle the API
		    # It's better if your service is up and running but not throttling API, then to have it throw errors for all users
		    # Make sure you monitor your redis-server so that it's never down. monit is a great tool for that.
		  end
    end
    @app.call(env)
  end

  def bad_request
    body_text = "Bad Request"
    [ 400, { 'Content-Type' => 'text/plain', 'Content-Length' => body_text.size.to_s }, [body_text] ]
  end

  def over_rate_limit
    body_text = "Over Rate Limit"
    [ 503, { 'Content-Type' => 'text/plain', 'Content-Length' => body_text.size.to_s }, [body_text] ]
  end
end