application.rb

# Add this line to your config/application.rb to enable
# initialization of Ripple, after the other framework railties
require 'ripple/railtie'

# To use the Riak cache store, place this line inside the 
# Application class
config.cache_store = :riak_store

files_controller.rb

# Stores files in Riak, redirects their download to reverse-proxy through nginx
class FilesController < ApplicationController
  def index
    @files = Ripple.client['files'].keys
  end

  def create
    uploaded = params[:file]
    key = ::File.basename(uploaded.original_filename)
    Ripple.client['files'].new(key).tap do |robj|
      robj.data = uploaded.read
      robj.content_type = uploaded.content_type
      robj.store
    end
    redirect_to files_path
  end

  def show
    key = [params[:id],params[:format]].compact.join(".")
    if Ripple.client['files'].exists?(key)
      headers["X-Accel-Redirect"] = "/riak/files/#{key}"
      head :ok
    else
      redirect_to files_path
    end
  end
end

index.html.erb

<!-- this is the index view for the FilesController -->
<h1>Files</h1>
<ul>
<% @files.each do |file| %>
<li><%= link_to file, "/files/#{file}" %></li>
<% end %>
</ul>
<h2>Upload a file</h2>
<%= form_tag files_path, :multipart => true do %>
  <%= file_field_tag :file %>
  <%= submit_tag "Upload" %>
<% end %>

nginx.conf

# Sets up internal redirects to Riak backend, for X-Accel-Redirect file-serving
# Thanks to Pat Allan (@pat) for most of this config.
daemon off;

events {
  worker_connections  1024;
}

http {
  include /usr/local/etc/nginx/mime.types;
  
  # Assuming path has been set to a Rails application
  access_log            log/nginx.access.log;
  error_log             log/nginx.error.log;

  client_body_temp_path tmp/nginx.client_body_temp;
  fastcgi_temp_path     tmp/nginx.client_body_temp;
  proxy_temp_path       tmp/nginx.proxy_temp;
  
  # Replace this with whatever `passenger-config --root` outputs
  passenger_root /Users/sean/.rvm/gems/ruby-1.9.2-rc2@webinar/gems/passenger-2.2.15;
  # Replace this with whatever `which ruby` outputs
  passenger_ruby /Users/sean/.rvm/rubies/ruby-1.9.2-rc2/bin/ruby;

  # Riak reverse-proxy configuration
  upstream riak {
    server localhost:8098;
    # server riak2:8098;
    # server riak3:8098;
  }
  
  server {
    listen      3000;
    server_name localhost;
    
    root              public;
    passenger_enabled on;
    rails_env         development;

    # Target for X-Accel-Redirect responses
    location /riak {
      internal;
      proxy_pass http://riak/riak;
    }
  }
}

nginx.sh

#!/usr/bin/env bash
nginx -p `pwd`/ -c `pwd`/config/nginx.conf \
  -g "error_log `pwd`/log/nginx.error.log; pid `pwd`/log/nginx.pid;";

ripple.yml

# config/ripple.yml
# Just like database.yml - one key per environment

development:
  host: 127.0.0.1
  port: 8098

test: &TEST
  host: 127.0.0.1
  port: 9000

production:
  host: prod-riak-host
  port: 8098

cucumber:
  <<: *TEST