Example of a Rack application that takes advantage to body.each to simulate a real-time data feed.

RackServer.rb

# Example of a Rack application that takes advantage to body.each to simulate
# a real-time data feed.
#
# Anyone may use this code AT YOUR OWN RISK.

require 'rack'
require 'ebb'

#This class simulates a server waiting for events.  it will yield a line with one of the HTTP Request
#headers every half second.  If things work right you should see you browser window slowely fill with
#request header lines as they are sent from the server.
class SlowIndex
  def initialize(env)
    @r = env.map{ |k,v| "#{k} => #{v}\n"}.sort
  end

  def each
    #This should be relpaced with real magic.  Anything yielded to the block will go out on the line.
    @r.each do |i|
      yield i
      sleep 0.5
    end
  end
end

#Our actual Rack application Ezra and David can both eat my shorts.  It is 0.007KLoC counting the
#coments. :)
class Server
  def call(env)
    [200, {"Content-Type" => "text/plain"}, SlowIndex.new(env)]
  end
end

#There is Rack Middle ware to do this but it was faster to role my own then read the RDocs.
class Observer
  def initialize(app)
    @app = app
  end

  def call(env)
    puts "Serving #{env['PATH_INFO']}"
    status, headers, body = @app.call(env)
    puts "  #{status}"
    [status, headers, body]
  end
end

#We are going to try to serve files if tey exist so we can make Ajax Requests.
#!!!Warning - This is a great way to comprimized the securty of a production server.  Always use
#Absolute Path names when not playing around.
app = Rack::Cascade.new([])
app << Rack::File.new('public/') # Serve Files from the public directory.
app << Server.new #Run our Micro App

s = Rack::Handler::Ebb #Ebb is much more friendly about sending out partial pages then Mongrel.
puts "** Starting Server **"
s.run(Observer.new(app), :Host=>'localhost', :Port=>4000)
puts "** Stopping Server **"