rollout¶ ↑

Conditionally roll out features with redis.

Install it¶ ↑

gem install rollout

How it works¶ ↑

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.

Groups¶ ↑

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)

Specific Users¶ ↑

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)

User Percentages¶ ↑

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)

Feature is broken¶ ↑

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.

Namespacing¶ ↑

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.

Implementations in other languages¶ ↑

• Python: github.com/asenchi/proclaim

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