Conditionally roll out features with redis.

gem install rollout

Initialize a rollout object. I assign it to a global var.

$redis   = Redis.new
$rollout = Rollout.new($redis)

Check whether a feature is active for a particular user:

$rollout.active?(:chat, User.first) # => true/false

You can activate features using a number of different mechanisms.

Rollout ships with one group by default: “all”, which does exactly what it sounds like.

You can activate the all group for the chat feature like this:

$rollout.activate_group(:chat, :all)

You might also want to define your own groups. We have one for our caretakers:

$rollout.define_group(:caretakers) do |user|
  user.caretaker?
end

You can activate multiple groups per feature.

Deactivate groups like this:

$rollout.deactivate_group(:chat, :all)

You might want to let a specific user into a beta test or something. If that user isn’t part of an existing group, you can let them in specifically:

$rollout.activate_user(:chat, @user)

Deactivate them like this:

$rollout.deactivate_user(:chat, @user)

If you’re rolling out a new feature, you might want to test the waters by slowly letting in a percentage of your users.

$rollout.activate_percentage(:chat, 20)

The algorithm for determining which users get let in is this:

user.id % 10 < percentage / 10

So, for 20%, users 0, 1, 10, 11, 20, 21, etc would be allowed in. Those users would remain in as the percentage increases.

Deactivate all percentages like this:

$rollout.deactivate_percentage(:chat)

Deactivate everybody at once:

$rollout.deactivate_all

For some of our less stable features, we are actually measuring the error rate using redis, and deactivating them automatically when it raises above a certain threshold. It’s pretty cool. See github.com/jamesgolick/degrade for the failure detection code.

Rollout separates its keys from other keys on the Redis server using the “feature” keyspace.

You can namespace keys further to support multiple environments by using the github.com/defunkt/redis-namespace gem.

$ns = Redis::Namespace.new(Rails.env, :redis => $redis)
$rollout = Rollout.new($ns)
$rollout.activate_group(:chat, :all)

This example would use the “development:feature:chat:groups” key.

• Python: github.com/asenchi/proclaim

• 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 © 2010 James Golick, Protose, Inc. See LICENSE for details.