this is demo add-on that shows how one could log and modify an HTTP request before it hits a Heroku application.
it expects the user to install my rack-cgi-proxy and configure it via:
Gemfile:
gem 'rack-cgi-proxy', :git => 'git://github.com/csquared/rack-cgi-proxy.git'
config.ru
use Rack::CgiProxy, ENV['REQUEST_LOGGER_URL']
Install Add-on
heroku addons:add request-logger