checking_work.ex

  def handle_info(:schedule_work, state) do
    unless :queue.is_empty(state) do
      for _ <- 0..System.schedulers_online() do
        Task.Supervisor.async_nolink(CrawlerExample.WorkerSupervisor, fn ->
            CrawlerExample.Worker.work(@depth_limit)
        end)
      end
    end

    schedule_work(@work_interval)

    {:noreply, state}
  end

  def handle_info({_, :ok}, state), do: {:noreply, state}
  def handle_info({:DOWN, _, :process, _pid, _exception}, state), do: {:noreply, state}
  
  defp schedule_work(interval), do: :erlang.send_after(interval, self(), :schedule_work)