Puma plugin to stop via Redis on Heroku

puma.rb

# === Plugins ===
require './lib/puma/plugin/redis_stop_puma'
plugin 'redis_stop_puma'

redis_stop_puma.rb

require 'puma/plugin'
require 'redis'

Puma::Plugin.create do
  def start(launcher)

    hostname = ENV['DYNO']
    return unless hostname

    redis = Redis.new(url: ENV.fetch('REDIS_URL', nil))
    return unless redis.ping == 'PONG'

    in_background do
      while true
        sleep 2
        if message = redis.get("puma::restart::#{hostname}")
          redis.del("puma::restart::#{hostname}")
          $stderr.puts message
          launcher.stop
          break
        end
      end
    end
  end
end