title: Scrapy:Using proxy middleware settings error
body: <p>I'm a scrapy newbie.I want to use proxy middleware.But my DEBUG messages show </p>
  
  <pre><code>2018-09-10 21:15:57 [scrapy.core.engine] INFO: Spider opened
  2018-09-10 21:15:57 [scrapy.extensions.logstats] INFO: Crawled 0 pages (at 0 pages/min), scraped 0 items (at 0 items/min)
  2018-09-10 21:15:57 [scrapy.extensions.telnet] DEBUG: Telnet console listening on 127.0.0.1:6023
  2018-09-10 21:16:57 [scrapy.extensions.logstats] INFO: Crawled 0 pages (at 0 pages/min), scraped 0 items (at 0 items/min)
  2018-09-10 21:17:57 [scrapy.extensions.logstats] INFO: Crawled 0 pages (at 0 pages/min), scraped 0 items (at 0 items/min)
  2018-09-10 21:18:05 [scrapy.downloadermiddlewares.retry] DEBUG: Retrying &lt;GET https://www.zhipin.com/robots.txt&gt; (failed 1 times): TCP connection timed out: 110: Connection timed out.
  2018-09-10 21:18:57 [scrapy.extensions.logstats] INFO: Crawled 0 pages (at 0 pages/min), scraped 0 items (at 0 items/min)
  </code></pre>
  
  <p>It will always crawl 0 pages and retry.My proxies are free and no authorization required.But I try to delete proxy middleware and use</p>
  
  <p><code>yield scrapy.Request(url='https://www.example.com/', callback=self.parse_first, meta=my_proxy)</code></p>
  
  <p>It's ok.It seems to be a problem with my settings.</p>
  
  <p>Settings</p>
  
  <pre><code>DOWNLOADER_MIDDLEWARES = {
  'scrapy.downloadermiddlewares.httpproxy.HttpProxyMiddleware':135,
  'ip_proxy.middlewares.CustomProxyMiddleware':125
  }
  </code></pre>
  
  <p>CustomProxyMiddleware</p>
  
  <pre><code>class CustomProxyMiddleware(object):
  def process_request(self, request, spider):
      request.meta['proxy'] = my_proxy
  </code></pre>
  
  <p>Spider</p>
  
  <pre><code>class ipSpider(scrapy.Spider):
    name = "test"
  
    def start_requests(self):
        yield scrapy.Request(url="https://www.example.com",callback=self.parse_first)
  </code></pre>