h1. Rails Metal, Rack, and Sinatra

Adam Wiggins

Raise of hands: More people know about pot than about Rails metal

h2. Rails Metal is a gateway to the world of Rack

h2. What can you do with Metal?

h3. Replace selected URLs for a speed boost

Example: Auction site (eBay on Rails)
The auction show page is probably hit the most (example with Rick Astley: Greatest Hits - laughs)

Most traffic goes to: GET /auctions/id.xml
We can get a big benefit from replacing just that URL

h4. Standard Rails

AuctionsController with format.xml

h4. Metal

app/metal/auctions_api.rb

class AuctionsApi
  def self.call(env)
    url_pattern = %r{/auctions/(\d+).xml} # Do your own routing
    
    if m = env['PATH_INFO'].match(url_pattern)
      # render the auction api
      auction = Auction.find(m[1])
      [200, {"Content-Type" => "text/xml"}, auction.to_xml] # Return value from rack
    else
      # pass - do nothing
      [400, {}] # Return value from rack
    end
  end
end

h2. What is Rack?

It stands between frameworks as Rails and web servers.

Ruby Isn't Just about Rails (slides available in SlideShare)

h3. An explosion of Ruby project in the past 2 years

h4. Web Layer

ActionController
Merb
Sinatra

h4. ORM

ActiveRecord
Datamapper
Sequal

h4. Tests/Specs

Test::Unit
RSpec
Shoulda

h4. Templating

Erb
HAML
Erubis

h4. HTTP Client

ActiveResource
RestClient
HTTParty

h4. Web server

Mongrel
Thin
Ebb

h3. Rails are from Mars, Rack are from Venus

But starting from Rails 2.3, Rails is now based in Rack

Rails Metal is where the genious is here, it lets us tap into the great things in Rack-land
This will be very uniting for the Ruby community

h3. The world of Rack is now within the reach from Rails

How does that happen?

h2. Sinatra

The classy microframework for RUby
http://sinatrarb.com

h3. Example

require 'rubygems'
require 'sinatra'

get '/hello' do
  "Hello, whirled"
end

This is not a snippet, this is a full Sinatra Application

h3. A minimalist paradise

post 'articles'
  article = Article.create! params
  redirect "/articles/#{article.id}"
end

get '/articles/:id' do
  @article = Article.find(params[:id])
  erb :article
end

h3. Sinatra in our Rails app?

We can replace selected URLs for a speed boost - or we can replace them with Sinatra

h4. Example - app/metal/articles.rb

class Articles < Sinatra::Application
  set :environment, 'production'
  
  ... (same code as above)
end

You can stick this right into an existing Rails app.

h3. Replacing the pure Rack example with Sinatra

The AuctionApi example is very verbose

But the Sintra example is minimalist:

get '/auctions/:id.xml' do
  Auction.find params[:id].to_xml
end

h2. Resources

http://railscasts.com/episodes/150-rais-metal
rack.rubyforge.or
sinatrarb.com
adam.blog.heruko.com

h2. Questions

h3. What's the speed difference between using Rack and Sinatra for Metal?

It will give you a real speed boost, but you shouldn't do it just for that