em-proxy-http.rb

require 'em-proxy'

host = "0.0.0.0"
port = 9889
puts "listening on #{host}:#{port}..."

Sessions = {}

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

  conn.on_connect do|data,b|
    puts [:on_connect, data, b].inspect
  end

  # modify / process request stream
  conn.on_data do |data|
    if data.match(/^[GET|POST]/)
      raw_headers = data.split("\n").map{|h| h.strip }
      req_method = raw_headers.shift
      headers = {}

      raw_headers.each do|kv|
        next if kv.strip == ''
        key   = kv.gsub(/:.*$/,'').strip.downcase
        value = kv.gsub(/.*:/,'').strip
        headers[key] = value
      end
      session_token = "#{headers['host']}_#{Time.now.to_i}_#{req_method}"
      session_port = headers['host'].split(':').last.to_i || 80
      session_port = 80 if session_port == 0
      puts "using port: #{session_port.inspect}"
      conn.server session_token, :host => headers['host'], :port => session_port

      #puts [:on_data, data].inspect
      puts "New session: #{session_token} (#{req_method})"
    end

    data
  end

  # modify / process response stream
  conn.on_response do |backend, resp|
    puts [:on_response, backend, resp].inspect
    resp
  end

  # termination logic
  conn.on_finish do |backend, name|
    puts [:on_finish, name].inspect

    # terminate connection (in duplex mode, you can terminate when prod is done)
    # unbind if backend == :srv
  end
end

did a little more digging and realized I can switch connections by doing this:

session_token = "#{headers['host']}_#{Time.now.to_i}"
conn.server session_token, :host => headers['host'], :port => 80

Not sure if session_token is the right name for this identifier yet... but this looks more promising now

Revised to change the conn server identifier by request name...

Having some problems with this approach - connections are definitely getting mixed... so the wrong response is being sent to some requests...