class Sidekiq::Queue

def latency
  entry = Sidekiq.redis { |conn|
    conn.lindex(@rname, -1)
  }
  return 0.0 unless entry
  job = Sidekiq.load_json(entry)
  enqueued_at = job["enqueued_at"]
  if enqueued_at
    if enqueued_at.is_a?(Float)
      # old format
      now = Time.now.to_f
      now - enqueued_at
    else
      now = ::Process.clock_gettime(::Process::CLOCK_REALTIME, :millisecond)
      (now - enqueued_at) / 1000.0
    end
  else
    0.0
  end
end