modifications needed to act as buffering reverse proxy on heroku

app_name.ru

$stdout.sync = true
require ::File.expand_path('../config/environment',  __FILE__)
run AppName::Application

config.ru

require 'rubygems'
require 'bundler'
$stdout.sync = true
Bundler.require(:rack)

puts ARGV
$port = ARGV.first
SERVERS = 1
ROOT = '.'

spawn("foreman start worker")
require './proxy'

# Start proxy
BalancingProxy::Server.run

Procfile

web: ruby config.ru $PORT
worker: bundle exec thin start -R app_name.ru --socket tmp/thin.sock -e production

proxy.rb

  module Server
    def run(host='0.0.0.0')

      puts "Launching proxy at #{host}:#{$port}...\n"

      Proxy.start(:host => host, :port => $port, :debug => false) do |conn|

        Backend.select do |backend|
          @connection_process = Proc.new do |backend,count|
             begin
             conn.server backend, :socket => backend.socket
             conn.on_connect  &Callbacks.on_connect
             conn.on_data     &Callbacks.on_data
             conn.on_response &Callbacks.on_response
             conn.on_finish   &Callbacks.on_finish
             rescue RuntimeError
               unless count > 4
		 EM.add_timer(20) do
                    @connection_process.call backend, (count+1)
                 end
               end
             end
          end
          @connection_process.call backend, 0
        end
      end
    end

    module_function :run
  end