lib/opbeans_shuffle.rb

require 'http'

class OpbeansShuffle
  def initialize(app, test, services:, probability:)
    @app = app
    @test = Regexp.new(test)
    @services = services.split(',')
    @probability = Float(probability)
  end

  def call(env)
    path = env['PATH_INFO']

    if @test =~ path && rand < @probability && @services.any?
      lucky_winner = @services.sample
      Rails.logger.info "Proxying #{path} to #{lucky_winner}"

      unless lucky_winner.start_with?('http://')
        lucky_winner = "http://#{lucky_winner}:3000"
      end

      Timeout.timeout(15) do
        resp = HTTP.get("#{lucky_winner}#{path}")

        [
          resp.status,
          { 'Content-Type' => resp.headers['Content-Type'] || 'text/plain' },
          resp.body
        ]
      end
    else
      @app.call(env)
    end
  rescue Timeout::Error
    Rails.logger.error "Connection to #{lucky_winner} timed out after 15s"
    raise
  end
end