   def handle_info(:crawl, spider) do
     options = spider.options
     urls = options[:urls] || []
+    Logger.debug("Starts a crawl for #{urls}")
 
     args = [urls, spider.state]
     spider = case call(:start_requests, spider, args) do

  defmacro __using__(_) do
    quote location: :keep do
      @behaviour GenSpider

      @start_urls []


  def request(url, callback, from \\ self) do
    Request.async(url, callback, from)
  end

  def await(request = %Request{}), do: Request.await(request)
  def await(spider, timeout \\ :infinity) do
    GenServer.call(spider, :await, timeout)
  end

  # GenServer callbacks
