Custom response based on source request

[jeffcarbs]

Use-case

My company's main web application (heroku) and marketing site (wordpress) are served at the same subdomain (www). The root/empty path (e.g. https://www.mysite.com) and some other whitelisted paths are reverse-proxied to wordpress, while the rest are served by a Rails app.

We wanted to make it such that if a request comes in for the root path AND they have a specific cookie (a session cookie for our app), redirect them into the application. Otherwise, reverse-proxy as usual to wordpress.

Solution

Currently I've monkey-patched this gem to support this use-case:

module RackReverseProxy
  class RoundTrip
    private

    alias_method :proxy_original, :proxy

    def proxy
      return app.call(env) if uri.nil?

      if options[:custom_response]
        response = options[:custom_response].call(source_request)
        return response if response
      end

      proxy_original
    end
  end
end

# In config.ru:
custom_response = proc do |request|
  [302, { 'Location' => "#{request.base_url}/app" }, []] if request.cookies['_my_app_session']
end

reverse_proxy(/^$/, passback_host, :custom_response => custom_response)

Just wondering if this is something other people have run into and/or this is something you'd want to bake into this gem. I'm happy turn this into a PR if so.