dump_request.rb

require 'pathname'

class DumpRequst
  def initialize(app, dir, &out_strategy)
    @app = app
    @dir = dir
    @out_strategy = out_strategy
    Pathname.new(dir).mkpath unless File.directory?(dir)
  end

  def call(env)
    e = env.dup
    body = e.delete("rack.input")
    rack, http = separate_env(e)
    begin
      File.open(filename, "w") do |f|
        http.each{|k,v| f.puts "#{k} : #{v}" }
        f.puts("\n")
        rack.each{|k,v| f.puts "#{k} : #{v}" }
        f.puts("\n")
        f.write body.read
      end
    rescue => ignore
    ensure
      body.rewind if body.respond_to?(:rewind)
    end
    @app.call(env)
  end

  private
  def filename
    if @out_strategy
      @out_strategy.call(@dir)
    else
      t = Time.now
      fname = "%s.%03d.dat" % [t.strftime("%Y%m%d-%H%M%S"), (t.usec/1000.0).round]
      File.expand_path(fname, @dir)
    end
  end

  def separate_env(env)
    env.to_a.sort_by(&:first).partition{|k,v| k =~ /\Arack\./ }
  end
end

ActionController::Dispatcher.middleware.use ::DumpRequst, File.expand_path("tmp/dump-req", Rails.root)