duplex_proxy.rb

require 'em-proxy'

Proxy.start(:host => "127.0.0.1", :port => 8080) do |conn|
  @start = Time.now
  @data = Hash.new("")

  conn.server :prod, :host => "db.wasiutynski.net", :port => 80   # production, will render resposne
  conn.server :test, :host => "127.0.0.1", :port => 5984          # testing, internal only

  conn.on_data do |data|
    # rewrite User-Agent
    data.gsub(/User-Agent: .*?\r\n/, "User-Agent: em-proxy/0.1\r\n")
  end
 
  conn.on_response do |server, resp|
    # only render response from production
    @data[server] += resp
    resp if server == :prod
  end

  conn.on_finish do |name|
    p [:on_finish, name, Time.now - @start]
    p @data
  end
end

# $ ruby duplex_proxy.rb &
# $ curl http://localhost:8080/krug
# {"db_name":"krug","doc_count":3,"doc_del_count":0,"update_seq":3,"purge_seq":0,"compact_running":false,"disk_size":12377,"instance_start_time":"1272355167598548","disk_format_version":5}
# [:on_finish, :prod, 0.08536626]
# {:test=>"HTTP/1.1 200 OK\r\nServer: CouchDB/0.11.0 (Erlang OTP/R13B)\r\nDate: Tue, 27 Apr 2010 09:44:46 GMT\r\nContent-Type: text/plain;charset=utf-8\r\nContent-Length: 189\r\nCache-Control: must-revalidate\r\n\r\n{\"db_name\":\"krug\",\"doc_count\":2,\"doc_del_count\":1,\"update_seq\":14,\"purge_seq\":0,\"compact_running\":false,\"disk_size\":180313,\"instance_start_time\":\"1272353276038978\",\"disk_format_version\":5}\n", 
#  :prod=>"HTTP/1.1 200 OK\r\nServer: nginx/0.5.36\r\nDate: Tue, 27 Apr 2010 09:44:47 GMT\r\nContent-Type: text/plain;charset=utf-8\r\nConnection: keep-alive\r\nContent-Length: 187\r\nCache-Control: must-revalidate\r\n\r\n{\"db_name\":\"krug\",\"doc_count\":3,\"doc_del_count\":0,\"update_seq\":3,\"purge_seq\":0,\"compact_running\":false,\"disk_size\":12377,\"instance_start_time\":\"1272355167598548\",\"disk_format_version\":5}\n"}
# [:on_finish, :test, 0.085606746]