クライアントからやってくる本物のHTTPリクエストをダンプする ref: http://qiita.com/udzura/items/db49fc086cff2a8aaea3

file1.txt

$ ruby http-dumper.rb  -p 3002

file3.txt

$ ruby kage-front.rb -p 3000 --backend-port=3001 --dumper-port=3002

http-dumper.rb

# -*- coding: utf-8 -*-
require 'optparse'
require 'webrick'
require 'json'
options = ARGV.getopts("p:", "port:")

# The :monkey: raises
# cf. http://d.hatena.ne.jp/vividcode/20110505/1304618393
class WEBrick::HTTPServlet::ProcHandler
  alias do_PUT    do_POST
  alias do_DELETE do_POST
end

HORIZON = "\e[31m" + ("#" * 72) + "\e[0m"

def dump_http_request(req)
  puts HORIZON
  puts req.request_line
  puts req.raw_header
  puts
  if body = req.body
    puts body.lines.map{|line| line.gsub /[[:cntrl:]]/, '' }
  else
    puts "\e[35m*** Empty request body (maybe it is GET) ***\e[0m"
  end
  puts HORIZON
  puts
end

srv = WEBrick::HTTPServer.new(
  :BindAddress => "0.0.0.0",
  :Port => (options["p"] || options["port"] || raise("Need option -p=PORT")).to_i,
)

srv.mount_proc "/" do |req, res|
  dump_http_request(req)

  res.content_type = "application/json"
  res.body = {return: "OK"}.to_json
end

Signal.trap('INT') { srv.shutdown }
srv.start

kage-front.rb

require 'optparse'
require 'kage'

options = ARGV.getopts("p:", "port:", "backend-port:", "dumper-port:")

Kage::ProxyServer.start do |server|
  server.port = (options["p"] || options["port"] || raise("Need option -p=PORT")).to_i
  server.host = '0.0.0.0'
  server.debug = false

  server.add_master_backend(:dev, 'localhost', options["backend-port"])
  server.add_backend(:dump, 'localhost', options["dumper-port"])

  server.on_select_backends do |request, headers|
    # アセットまでdump serverに送るのはうざったいので適当に振り分ける
    is_asset = request[:path] =~ /\.(ico|js|css|gif|png|jpe?g)$/
    is_asset ? [:dev] : [:dev, :dump]
  end

  puts "Server is listening 0.0.0.0:#{server.port}"
end