Question

为了不被反爬虫机制检测到，主要采用了伪造随机User-Agent、自动限速、禁用Cookie等措施。

1.伪造随机User-Agent

还是使用之前编写的中间件，代码如下：

  class RandomUserAgent(object):
  
     def __init__(self,agents):
       self.agents = agents
  
     @classmethod
     def from_crawler(cls,crawler):
       return cls(crawler.settings.getlist('USER_AGENTS'))
  
     def process_request(self,request,spider):
       request.headers.setdefault('User-Agent', random.choice(self.agents))

在settings中设置USER_AGENTS的值：

  USER_AGENTS = [
     "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1; AcooBrowser; .NET CLR 
       1.1.4322; .NET CLR 2.0.50727)",
     "Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 6.0; Acoo Browser; SLCC1; .NET 
       CLR 2.0.50727; Media Center PC 5.0; .NET CLR 3.0.04506)",
     "Mozilla/4.0 (compatible; MSIE 7.0; AOL 9.5; AOLBuild 4337.35; Windows NT 
       5.1; .NET CLR 1.1.4322; .NET CLR 2.0.50727)",
     "Mozilla/5.0 (Windows; U; MSIE 9.0; Windows NT 9.0; en-US)",
     "Mozilla/5.0 (compatible; MSIE 9.0; Windows NT 6.1; Win64; x64; Trident/5.0; .NET 
       CLR 3.5.30729; .NET CLR 3.0.30729; .NET CLR 2.0.50727; Media Center PC 6.0)",
     "Mozilla/5.0 (compatible; MSIE 8.0; Windows NT 6.0; Trident/4.0; WOW64; 
       Trident/4.0; SLCC2; .NET CLR 2.0.50727; .NET CLR 3.5.30729; .NET CLR 
       3.0.30729; .NET CLR 1.0.3705; .NET CLR 1.1.4322)",
     "Mozilla/4.0 (compatible; MSIE 7.0b; Windows NT 5.2; .NET CLR 1.1.4322; .NET 
       CLR 2.0.50727; InfoPath.2; .NET CLR 3.0.04506.30)",
     "Mozilla/5.0 (Windows; U; Windows NT 5.1; zh-CN) AppleWebKit/523.15 (KHTML, 
       like Gecko, Safari/419.3) Arora/0.3 (Change: 287 c9dfb30)",
     "Mozilla/5.0 (X11; U; Linux; en-US) AppleWebKit/527+ (KHTML, like Gecko, 
       Safari/419.3) Arora/0.6",
     "Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.8.1.2pre) Gecko/20070215 
       K-Ninja/2.1.1",
     "Mozilla/5.0 (Windows; U; Windows NT 5.1; zh-CN; rv:1.9) Gecko/20080705 
       Firefox/3.0 Kapiko/3.0",
     "Mozilla/5.0 (X11; Linux i686; U;) Gecko/20070322 Kazehakase/0.4.5",
     "Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9.0.8) Gecko Fedora/1.9.0.8-1.fc10 
       Kazehakase/0.5.6",
     "Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/535.11 (KHTML, like Gecko) 
       Chrome/17.0.963.56 Safari/535.11",
     "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_7_3) AppleWebKit/535.20 (KHTML, like 
       Gecko) Chrome/19.0.1036.7 Safari/535.20",
     "Opera/9.80 (Macintosh; Intel Mac OS X 10.6.8; U; fr) Presto/2.9.168 Version/
       11.52",
     "Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/536.11 (KHTML, like Gecko) 
       Chrome/20.0.1132.11 TaoBrowser/2.0 Safari/536.11",
     "Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.1 (KHTML, like Gecko) 
       Chrome/21.0.1180.71 Safari/537.1 LBBROWSER",
     "Mozilla/5.0 (compatible; MSIE 9.0; Windows NT 6.1; WOW64; Trident/5.0; 
       SLCC2; .NET CLR 2.0.50727; .NET CLR 3.5.30729; .NET CLR 3.0.30729; Media 
       Center PC 6.0; .NET4.0C; .NET4.0E; LBBROWSER)",
     "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1; QQDownload 
       732; .NET4.0C; .NET4.0E; LBBROWSER)",
     "Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/535.11 (KHTML, like Gecko) 
       Chrome/17.0.963.84 Safari/535.11 LBBROWSER",
     "Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 6.1; WOW64; Trident/5.0; 
       SLCC2; .NET CLR 2.0.50727; .NET CLR 3.5.30729; .NET CLR 3.0.30729; Media 
       Center PC 6.0; .NET4.0C; .NET4.0E)",
     "Mozilla/5.0 (compatible; MSIE 9.0; Windows NT 6.1; WOW64; Trident/5.0; 
       SLCC2; .NET CLR 2.0.50727; .NET CLR 3.5.30729; .NET CLR 3.0.30729; Media 
       Center PC 6.0; .NET4.0C; .NET4.0E; QQBrowser/7.0.3698.400)",
     "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1; QQDownload 
       732; .NET4.0C; .NET4.0E)",
     "Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 5.1; Trident/4.0; SV1; QQDownload 
       732; .NET4.0C; .NET4.0E; 360SE)",
     "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1; QQDownload 
       732; .NET4.0C; .NET4.0E)",
     "Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 6.1; WOW64; Trident/5.0; 
       SLCC2; .NET CLR 2.0.50727; .NET CLR 3.5.30729; .NET CLR 3.0.30729; Media 
       Center PC 6.0; .NET4.0C; .NET4.0E)",
     "Mozilla/5.0 (Windows NT 5.1) AppleWebKit/537.1 (KHTML, like Gecko) Chrome/
       21.0.1180.89 Safari/537.1",
     "Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.1 (KHTML, like Gecko) 
       Chrome/21.0.1180.89 Safari/537.1",
     "Mozilla/5.0 (iPad; U; CPU OS 4_2_1 like Mac OS X; zh-cn) AppleWebKit/533.17.9 
       (KHTML, like Gecko) Version/5.0.2 Mobile/8C148 Safari/6533.18.5",
     "Mozilla/5.0 (Windows NT 6.1; Win64; x64; rv:2.0b13pre) Gecko/20110307 Firefox/
       4.0b13pre",
     "Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:16.0) Gecko/20100101 Firefox/16.0",
     "Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.11 (KHTML, like Gecko) 
       Chrome/23.0.1271.64 Safari/537.11",
     "Mozilla/5.0 (X11; U; Linux x86_64; zh-CN; rv:1.9.2.10) Gecko/20100922 Ub
       untu/10.10 (maverick) Firefox/3.6.10"
  ]

并启用该中间件：

  DOWNLOADER_MIDDLEWARES = {
     'scrapy.downloadermiddlewares.useragent.UserAgentMiddleware': None,
     'yunqiCrawl.middlewares.RandomUserAgent.RandomUserAgent': 410,
  }

2.自动限速的配置

  DOWNLOAD_DELAY=2
  AUTOTHROTTLE_ENABLED=True
  AUTOTHROTTLE_START_DELAY=5
  AUTOTHROTTLE_MAX_DELAY=60

3.禁用Cookie

  COOKIES_ENABLED=False

采取以上措施之后如果还是会被发现的话，可以写一个HTTP代理中间件来更换IP。