Rack

Base de todo ruby web framework

Rails es una rack application..

Por que?

Que hace?

Envuelve el request y el response

Provee una interfaz común para aplicaciones web

Permite que varias aplicaciones se encadenen juntas(Middleware).

Applicacion Rack

Clase ruby con un metodo "call"

Acepta un parametro(env) con informacion sobre el request.

Devuelve un array:

[status_code, {headers}, [body]]

require "rack"
require "thin"

class HelloWorld
  def call(env)
    [ 200, { "Content-Type" => "text/plain" }, ["Hello World"] ]
  end
end

Rack::Handler::Thin.run HelloWorld.new

Lambda

require "rack"
require "thin"

app = -> (env) do
  [ 200, { "Content-Type" => "text/plain" }, env ]
end

Rack::Handler::Thin.run app

Rack Application server

Una clase dentro del modulo Rack::Handler

Tiene un metodo run al que se le pasa una applicacion rack.

Llama el metodo "call" de la aplicacion y le pasa el parametro env.

require 'rack'

@app = MyApp.new

Rack::Handler::Puma.run(@app)

Text

https://github.com/puma/puma/blob/master/lib/rack/handler/puma.rb

Middleware

Requerimientos

los mismos que una applicacion rack.

Initialize que acepta un objeto app

Normalmente llama a app.call

require "rack"
require "thin"

app = -> (env) do
  sleep 3
  [ 200, { "Content-Type" => "text/plain" }, ["Hello World\n"] ]
end

class LoggingMiddleware
  def initialize(app)
    @app = app
  end

  def call(env)
    before = Time.now.to_i
    status, headers, body = @app.call(env)
    after = Time.now.to_i
    log_message = "App took #{after - before} seconds."

    [status, headers, body << log_message]
  end
end

Rack::Handler::Thin.run LoggingMiddleware.new(app)

Rack::Builder

app =
Rack::Builder.new do |builder|
  builder.use FilterLocalHost
  builder.run RackApp.new
end

Rack::Handler::Thin app

Demo...

Middlewares out of the box

Rack::URLMap, to route to multiple applications inside the same process.
Rack::CommonLogger, for creating Apache-style logfiles.
Rack::ShowException, for catching unhandled exceptions and presenting them in a nice and helpful way with clickable backtrace.
Rack::File, for serving static files.