SmoothChange

Deploy breaking changes on your API smoothly.

Add this line to your application's Gemfile:

gem 'smooth_change'

And then execute:

$ bundle install

Or install it yourself as:

$ gem install smooth_change

# config/initializers/smooth_change.rb
SmoothChange.configure do |config|
  config.adapter = SmoothChange::Adapters::Yaml.new(
    file: Rails.root.join("config/smooth_change.yml")
  )
end

# config/smooth_change.yml
features:
  kittens_pagination:
    mode: opt_in
  new_kitten_filter:
    mode: opt_out

Clients can express there feature capabilities using request header X-FeatureCapabilities. It expects a comma separated values of each feature preferences :

• name of the feature you are ready to receive
• name precessed with a ! of feature you are not ready to receive

Exemple : X-FeatureCapabilities: !kittens_pagination,new_kitten_filter

Will result in :

• kittens_pagination: not ready
• new_kitten_filter: ready

Simply include SmoothChange::ActionController::Helper in your controllers (or ApplicationController). This module provides a #smooth_change helper responding to #enabled?(feature_name)

Exemple :

require "smooth_change"

class ApplicationController < ActionController::API
  include SmoothChange::ActionController::Helper
end

class MyApiController < ActionController::API
  def index
    kittens = Kittens.all
    
    # Adding pagination may break some front-end clients
    if smooth_change.enabled?(:kittens_pagination)
      kittens = kittens.page(params[:page])
    end
    
    render json: kittens
  end
end

If you want to use this feature flags in your models, call store_smooth_change in a before_action callback. This will store the smooth_change object in a ActiveSupport::CurrentAttributes (see Rails documentation)

To access it, call SmoothChange::Current.smooth_change. You can also use enabled? direcly with SmoothChange::Current

Example:

require "smooth_change"

class ApplicationController < ActionController::API
  include SmoothChange::ActionController::Helper

  before_action :store_smooth_change
end

class MyApiController < ActionController::API
  def index
    kittens = ComplexKittenFilter.new(Kitten.all, params).call
    render json: kittens
  end
end

# app/services/complex_kitten_filter.rb
class ComplexKittenFilter < ComplexFilter
  def call
    if SmoothChange::Current.enabled?(:new_kitten_filter)
      filter
    else
      legacy_filter
    end
  end
  
  private
  
  def legacy_filter
    # Do some old-school filtering ...
  end
  
  def filter
    # Filter like the cool kids !
  end
end

After checking out the repo, run bin/setup to install dependencies. Then, run rake spec to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.

To install this gem onto your local machine, run bundle exec rake install. To release a new version, update the version number in version.rb, and then run bundle exec rake release, which will create a git tag for the version, push git commits and the created tag, and push the .gem file to rubygems.org.

• Response helpers
• Instrumentation and Monitoring
• Framework agnostic (remove dependencies from rails and move helpers to dedicated gem)

Bug reports and pull requests are welcome on GitHub at https://github.com/[USERNAME]/smooth_change. This project is intended to be a safe, welcoming space for collaboration, and contributors are expected to adhere to the code of conduct.

The gem is available as open source under the terms of the MIT License.

Everyone interacting in the SmoothChange project's codebases, issue trackers, chat rooms and mailing lists is expected to follow the code of conduct.