Middleware which lets you to execute arbitrary code just for a certain fraction of requests

Possible usecases could be: purging cache from time to time, doing A/B test for a fraction of users/reqests, probing something from the request, etc.

Add this line to your application's Gemfile:

gem 'rack-fraction'

And then execute:

$ bundle

Or install it yourself as:

$ gem install rack-fraction

The usage if fairly trivial: you disable the middleware or either modifiy the env or request:

# To disable middleware: pass 'modify: nil' (default)
Rack::Fraction.new(app, modify: nil) do |_|
	# disabled middleware
end

# To modify env: pass 'modify: :env'
Rack::Fraction.new(app, modify: :env, percent: 100) do |env|
  # middleware modifies env for 100% requests
  env << '👋'
end

# To modify response: pass 'modify: : response'
Rack::Fraction.new(app, modify: :response, percent: 50) do |*response|
  # middleware modifies response for 50% requests
  response = response.dup
  response.last << 'Bonjour!'
  response
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 tags, and push the .gem file to rubygems.org.

Bug reports and pull requests are welcome on GitHub at https://github.com/smileart/rack-fraction. This project is intended to be a safe, welcoming space for collaboration, and contributors are expected to adhere to the Contributor Covenant code of conduct.

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

Everyone interacting in the Rack::Fraction project’s codebases, issue trackers, chat rooms and mailing lists is expected to follow the code of conduct.