Simple environmental feature toggling (that works well with Rollout)

Keeping true to twelve-factor application principles http://12factor.net, this simple library uses environment variables, with a straightforward naming convention, to specify feature toggles.

If Rollout https://github.com/jamesgolick/rollout is present, it will pass through most rollout methods except active?, where a preliminary test is done to see if the environment toggle is active first.

When using a continuous delivery process, it is important to try to get all code integrated into the mainline as soon as possible. Feature toggles are favored over feature branches (http://www.infoq.com/interviews/jez-humble-martin-fowler-cd, http://martinfowler.com/bliki/FeatureToggle.html, http://fournines.wordpress.com/2011/11/20/feature-branches-vs-feature-toggles/, and http://blog.jayfields.com/2010/10/experience-report-feature-toggle-over.html) during the dev process (to guard against incomplete features being deployed to production).

Twelve-factor tells us to keep app configuration setting in environment variables. Hence this libaray adds a tiny bit of convention on how feature toggle env vars are spelled.

As the ultimate acceptance of a feature is the market response, this library has been designed to work with rollout.

Add this line to your application's Gemfile:

gem 'binflip'

And then execute:

$ bundle

Or install it yourself as:

$ gem install binflip

Set an environment variable following a FEATURE_[name] pattern:

Procfile

FEATURE_CHAT = 1
FEATURE_UPLOAD_VIDEO = 1

(Or set the ENV vars manually)

Then in application setup / initialization:

$toggle = Binflip.new

Check for toggles, using just the [name]:

$toggle.active?(:chat)
$toggle.active?(:upload_video)

NOTE: Absence of feature toggle env variable means the feature is not active.

Procfile

FEATURE_CHAT = 1
FEATURE_UPLOAD_VIDEO = 1

(Or set the ENV vars manually)

Then in application setup / initialization:

$redis = Redis.new
$toggle = Binflip.new($redis)

Check for toggles:

$toggle.active?(:chat, @user)
$toggle.active?(:upload_video, @user)

If Rollout is present, Binflip delegates all methods to it (such as activate_user).

Copyright (c) 2012 Brian Kaney

MIT License