FFlags

Feature flags that can be overwritten on the fly. It could be per instance or per environment. Depending on how you set your key, either dynamically per instance or constant per environment.

It uses Redis to store the information, and the size should be very small, depending on how many flags you need to track.

Add this line to your application's Gemfile:

gem 'fflags'

And then execute:

$ bundle

Or install it yourself as:

$ gem install fflags

To configure the FFlags,

FFlags.config { |config .. }

• If you want the flags to be unique per instance, you can use hostname of the instance as such:

FFlags.config do |config|
  config.key   = Socket.gethostname
  config.flags = { new_view: true }
end

• If you want the flags to be unique per environment, you can use the key as such:

FFlags.config do |config|
  config.key   = Rails.environment,
  config.flags = { new_view: true }
end

Then in the code,

# Verify if the flag is enabled
if FFlags.enabled?(:new_view)
  # Do something
end
# or
if FFlags.new_view?
  # Do something
end


# Overwrite flag
FFlags.toggle(:new_view)
# or
FFlags.set(:new_view, false)

# To reset, and get back to the default settings.
FFlags.reset

# To read all flags
FFlags.all

• Add the gem in Gemfile.

# Gemfile.rb

gem 'fflags'

• Add the initializer.

# config/initializer/fflags.rb

FFlags.config do |config|
  config.flags = { new_feature: true }
  ..
end

• Use the feature anywhere in your code.

if FFlags.new_feature?
  puts 'Enabled'
end

Sometimes you need to set a set of flags in 1 go. Ex. Staging to have an exact same flag configuration as in Production. You can use template for this.

Ex.

In the config,

FFlags.config do |config|
  config.flags = { feature1: true, feature2: true, feature3: true }
  config.templates = { production: { feature1: false, feature2: false, feature3: false } }
end

Then in your code,

FFlags.set_as_template(:production)

# To view all the templates
FFlags.templates

Sometimes you need to test flag with different value in your test. You can set block for that.

Ex. in rspec

describe "#eat_tofu" do
  context 'new feature enabled' do
    FFlags.set(new_feature: true) do
      # Do something
    end
  end
  
  context 'new feature disabled' do
    FFlags.set(new_feature: false) do
      # Do something
    end
  end
end

After checking out the repo, run bundle install to install dependencies. Then, run rspec to run the tests.

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 tags, and push the .gem file to rubygems.org.

Bug reports and pull requests are welcome on GitHub at https://github.com/faizalzakaria/fflags.

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