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Split

Split is a rack based ab testing framework designed to work with Rails, Sinatra or any other rack based app.

Split is heavily inspired by the Abingo and Vanity rails ab testing plugins and Resque in its use of Redis.

Requirements

Split uses redis as a datastore.

If you're on OS X, Homebrew is the simplest way to install Redis:

$ brew install redis
$ redis-server /usr/local/etc/redis.conf

You now have a Redis daemon running on 6379.

Setup

If you are using bundler add split to your Gemfile:

gem 'split'

Then run:

bundle install

Otherwise install the gem:

gem install split

and require it in your project:

require 'split'

Rails

Split is autoloaded when rails starts up, as long as you've configured redis it will 'just work'.

Sinatra

To configure sinatra with Split you need to enable sessions and mix in the helper methods. Add the following lines at the top of your sinatra app:

class MySinatraApp < Sinatra::Base
  enable :sessions
  helpers Split::Helper

  get '/' do
  ...
end

Usage

To begin your ab test use the ab_test method, naming your experiment with the first argument and then the different variants which you wish to test on as the other arguments.

ab_test returns one of the alternatives, if a user has already seen that test they will get the same alternative as before, which you can use to split your code on.

It can be used to render different templates, show different text or any other case based logic.

finished is used to make a completion of an experiment, or conversion.

Example: View

<% ab_test("login_button", "/images/button1.jpg", "/images/button2.jpg") do |button_file| %>
  <%= img_tag(button_file, :alt => "Login!") %>
<% end %>

Example: Controller

def register_new_user
  #See what level of free points maximizes users' decision to buy replacement points.
  @starter_points = ab_test("new_user_free_points", 100, 200, 300)
end

Example: Conversion tracking (in a controller!)

def buy_new_points
  #some business logic
  finished("buy_new_points")  #Either a conversion named with :conversion or a test name.
end

Example: Conversion tracking (in a view)

Thanks for signing up, dude! <% finished("signup_page_redesign") >

Overriding alternatives

For development and testing, you may wish to force your app to always return an alternative. You can do this by passing it as a parameter in the url.

If you have an experiment called button_color with alternatives called red and blue used on your homepage, a url such as:

http://myawesomesite.com?button_color=red

will always have red buttons. This won't be stored in your session or count towards to results.

Web Interface

Split comes with a Sinatra-based front end to get an overview of how your experiments are doing.

You can mount this inside your app using Rack::URLMap in your config.ru

require 'split/dashboard'

run Rack::URLMap.new \
  "/"       => Your::App.new,
  "/split" => Split::Dashboard.new

You may want to password protect that page, you can do so with Rack::Auth::Basic

Split::Dashboard.use Rack::Auth::Basic do |username, password|
  username == 'admin' && password == 'p4s5w0rd'
end

Configuration

You may want to change the Redis host and port Split connects to, or set various other options at startup.

Split has a redis setter which can be given a string or a Redis object. This means if you're already using Redis in your app, Split can re-use the existing connection.

String: Split.redis = 'localhost:6379'

Redis: Split.redis = $redis

For our rails app we have a config/initializers/split.rb file where we load config/split.yml by hand and set the Redis information appropriately.

Here's our config/split.yml:

development: localhost:6379
test: localhost:6379
staging: redis1.example.com:6379
fi: localhost:6379
production: redis1.example.com:6379

And our initializer:

rails_root = ENV['RAILS_ROOT'] || File.dirname(__FILE__) + '/../..'
rails_env = ENV['RAILS_ENV'] || 'development'

split_config = YAML.load_file(rails_root + '/config/split.yml')
Split.redis = split_config[rails_env]

Namespaces

If you're running multiple, separate instances of Split you may want to namespace the keyspaces so they do not overlap. This is not unlike the approach taken by many memcached clients.

This feature is provided by the [redis-namespace][rs] library, which Split uses by default to separate the keys it manages from other keys in your Redis server.

Simply use the Split.redis.namespace accessor:

Split.redis.namespace = "resque:GitHub"

We recommend sticking this in your initializer somewhere after Redis is configured.

Contributors

Special thanks to the following people for submitting patches:

  • Lloyd Pick
  • Jeffery Chupp

Note on Patches/Pull Requests

  • Fork the project.
  • Make your feature addition or bug fix.
  • Add tests for it. This is important so I don't break it in a future version unintentionally.
  • Commit, do not mess with rakefile, version, or history. (if you want to have your own version, that is fine but bump version in a commit by itself I can ignore when I pull)
  • Send me a pull request. Bonus points for topic branches.

Copyright

Copyright (c) 2011 Andrew Nesbitt. See LICENSE for details.

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