Rack

[dylanninin]

Rack provides a minimal interface between webservers that support Ruby and Ruby frameworks.

• Web Servers: like WEBrick, Mongrel, Puma etc.
• Interface:
  • Handlers: the respective handler for any supported Web Server
  • Middlewares: the request/response customized chain between Web Server and the framework
  • Adapters: the respective adapter for any Ruby/Ruby Framework
• Ruby/Ruby Frameworks: like Rails, Sinatra etc.

Request/Response

A HTTP request is a triplet consisting of a method and resource pair, a set of headers and an optional body while a HTTP response is in triplet consisting of a response code, a set of headers and an optional body.

app = Proc.new {|env|
  puts "#{Time.now}, env: #{env}"

  # status_code, headers, body
  [200, {}, ["Hello. The time is #{Time.now}"]]
}

puts app.call({}) # =>
#2016-08-01 13:59:43 +0800, env: {}
#[200, {}, [Hello. The time is 2016-08-01 13:59:43 +0800]

require 'rack'
puts Rack::Handler.constants # =>
#[CGI, FastCGI, WEBrick, LSWS, SCGI, Thin]

Rack::Handler::WEBrick.run app # =>
#[2016-08-01 14:01:05] INFO  WEBrick 1.3.1
#[2016-08-01 14:01:05] INFO  ruby 2.3.1 (2016-04-26) [x86_64-darwin15]
#[2016-08-01 14:01:05] INFO  WEBrick::HTTPServer#start: pid=71956 port=8080

################################################################################
#
# Terminal request with httpie
#
#http :8080
#HTTP/1.1 200 OK
#Connection: Keep-Alive
#Content-Length: 44
#Date: Mon, 01 Aug 2016 06:01:28 GMT
#Server: WEBrick/1.3.1 (Ruby/2.3.1/2016-04-26)
#
#Hello. The time is 2016-08-01 14:01:28 +0800
################################################################################

################################################################################
#
# Rack formatted log
#
#2016-08-01 14:01:28 +0800,
# env: {
#   "GATEWAY_INTERFACE"=>"CGI/1.1",
#   "PATH_INFO"=>"/",
#   "QUERY_STRING"=>"",
#   "REMOTE_ADDR"=>"127.0.0.1",
#   "REMOTE_HOST"=>"127.0.0.1",
#   "REQUEST_METHOD"=>"GET",
#   "REQUEST_URI"=>"http://localhost:8080/",
#   "SCRIPT_NAME"=>"",
#   "SERVER_NAME"=>"localhost",
#   "SERVER_PORT"=>"8080",
#   "SERVER_PROTOCOL"=>"HTTP/1.1",
#   "SERVER_SOFTWARE"=>"WEBrick/1.3.1 (Ruby/2.3 #.1/2016-04-26)",
#   "HTTP_HOST"=>"localhost:8080",
#   "HTTP_ACCEPT_ENCODING"=>"gzip, deflate",
#   "HTTP_USER_AGENT"=>"HTTPie/0.9.4",
#   "HTTP_CONNECTION"=>"keep-alive",
#   "HTTP_ACCEPT"=>"*/*",
#   "rack.version"=>[1, #3],
#   "rack.input"=>#<StringIO:0x007fede39d7730>,
#   "rack#.errors"=>#<IO:<STDERR>>,
#   "rack.multithread"=>true,
#   "rack#.multiprocess"=>false,
#   "rack.run_once"=>false,
#   "rack.url_scheme"=>"http",
#   "rack.hijack?"=>true,
#   "rack#.hijack"=>#<Proc:0x007fede39d75c8@/Users/dylanninin/.rvm/gems/ruby-2.3#.1/gems/rack-2.0.1/lib/rack/handler/webrick.rb:74 (lambda)>,
#   "rack#.hijack_io"=>nil,
#   "HTTP_VERSION"=>"HTTP/1.1",
#   "REQUEST_PATH"=>"/"
# }
#127.0.0.1 - - [01/Aug/2016:14:01:28 CST] "GET / HTTP/1.1" 200 44

References

• http://rack.github.io/
• https://github.com/rack/rack
• https://github.com/puma/puma
• http://rubylearning.com/blog/2013/04/02/whats-rack/
• http://insights.thoughtworkers.org/ruby-web-server/
• https://github.com/planetruby/awesome-webservers

[dylanninin]

Middleware

• in Rails Boot Process #7 , there's the wrapped app. https://github.com/rack/rack/blob/master/lib/rack/server.rb

   ...
   def start &blk
      ...
      server.run wrapped_app, options, &blk
    end
    ...
      def build_app(app)
        middleware[options[:environment]].reverse_each do |middleware|
          middleware = middleware.call(self) if middleware.respond_to?(:call)
          next unless middleware
          klass, *args = middleware
          app = klass.new(app, *args)
        end
        app
      end

      def wrapped_app
        @wrapped_app ||= build_app app
      end

[dylanninin]

The Onion Architecture is a awesome picture illustrating the middlewares around an App

Example：

• https://gist.github.com/dylanninin/4c41cff6da79ca1a6b8c4126eda2dea2