From Rails to the web server to client to browser - David Padilla (@dabit) - RailsConf 2013

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From Rails to the web server to client to browser

David Padilla @dabit

• Life of a request
  • Browser creates request
  • Sends it to webserver (Unicorn)
  • Sends it to Rails
  • Sends it to spaghetti code
  • HTML is returned
• Rack's job is to communicate between webservers and frameworks
• Only requirements of Rack app:
  • A class that responds to call, then returns [http_code, headers, body]
    • @app.call(env)
  • config.ru
    • require 'app'; run App.new
• Then call rackup on CLI
• PRY
  • You can cd into objects
  • ls lists all the methods
• Experimenting with #call
  • Rails::Application#call is the entry point
  • show-method call shows source code
  • Parameter in call is {"REQUEST_METHOD" => "GET", "PATH_INFO" => '/', "RACK.INPUT" => ""}
  • response[0] # => 200
  • response[1] # => Hash of headers, like 'Content-Length'
  • response[2] # => Array of body
• Web Request from browser to webserver
  • thin start
    • This calls Thin::Server.start('0.0.0', 3000, app)
    • It can make TcpServers (among other servers, like UnixServer)
    • EventMachine is used to start the server
    • Thin parses request into something Rack can use
    • Zed Shaw wrote the Mongrel parser C extension
  • Unicorn and Puma
    • Doesn't use EventMachine, instead it uses kgio (kinda complicated)
    • Eventually calls @app.call(env)
• David rolls his own webserver. Cool stuff.
  • Actually not as scary as I thought
• Don't try this at home, but play around and be curious
• David's Code on github