Enabling feature plugins via constraint

routes.rb

Rails.application.routes.draw do
  # to enable feature1, `touch tmp/feature1`
  class FeatureEnabledConstraint
    def matches?(request)
      match = request.path.match %r{/plugins/(?<feature_name>[^/]*)}
      Rails.logger.info "MATCHED #{request.path} with #{match.inspect}"
      File.exist?("tmp/#{match[:feature_name]}")
    end
  end

  class Feature1
    def self.call(env) = return [200, {}, ['feature 1']]
  end
  class Feature2
    def self.call(env) = return [200, {}, ['feature 2']]
  end
  class Feature3
    def self.call(env) = return [200, {}, ['feature 3']]
  end

  constraints(FeatureEnabledConstraint.new) { mount Feature1, at: '/plugins/feature1' }
  constraints(FeatureEnabledConstraint.new) { mount Feature2, at: '/plugins/feature2' }
  constraints(FeatureEnabledConstraint.new) { mount Feature3, at: '/plugins/feature3' }
end