Rack middleware that sends requests to different Sinatra apps based on some criteria (randomly in this example).

chooser_middleware.rb

require "sinatra/base"

class Foo < Sinatra::Base
  get "/" do
    "foo!"
  end
end


class Bar < Sinatra::Base
  get "/" do
    "bar!"
  end
end


class Chooser
  def initialize(app1, app2)
    @app1 = app1
    @app2 = app2
  end

  def call(env)
    if rand(2) == 0
      @app1.call(env)
    else
      @app2.call(env)
    end
  end
end

config.ru

require "./chooser_middleware.rb"

run Chooser.new(Foo, Bar)