EM-Proxy

EventMachine Proxy DSL for writing high-performance transparent / intercepting proxies in Ruby.

• Slides from RailsConf 2009: bit.ly/D7oWB
• GoGaRuCo notes & Slides: www.igvita.com/2009/04/20/ruby-proxies-for-scale-and-monitoring/

Simple port forwarding proxy

    Proxy.start(:host => "0.0.0.0", :port => 80, :debug => true) do |conn|
      conn.server :srv, :host => "127.0.0.1", :port => 81

      # modify / process request stream
      conn.on_data do |data|
        p [:on_data, data]
        data
      end

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

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

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

For more examples see the /examples directory.

• SMTP Spam Filtering
• Duplicating traffic
• Selective forwarding
• Beanstalkd interceptor
• etc.