Scrapy 反爬手段

主要策略：

• 动态设置 user agent
• 禁用 cookies
• 设置延迟下载
• 使用 Google cache（国内网络的影响所以放弃）
• 使用 IP 地址池（Tor project、 VPN 和代理 IP ）
• 使用 Crawlera（另开一篇详细讲）

1.创建 middlewares.py

scrapy 代理ip， user agent 的切换都是通过 DOWNLOADER_MIDDLEWARES 来进行控制：

import random
import base64
from settings import PROXIES

class RandomUserAgent(object):
	"""Randomly rotate user agents based on a list of predefined ones"""
	def __init__(self, agents):
		self.agents =agents
	
	@classmethod
	def from_crawler(cls, crawler):
		return cls(crawler.setting.getlist('USER_AGENT'))
	
	def process_request(self, request, spider):
		request.headers.setdefault('User-Agent',random.choice(self.agents))
	
class ProxyMiddleware(object):
	def process_request(self, request, spider):
		proxy = random.choice(PROXIES)
		if proxy['user_pass'] is not None:
			request.meta['proxy'] = "http://%s" % proxy['ip_port']
			encoded_ueser_pass = base64.encodestring(proxy['user_pass'])
			request.headers['Proxy_Authorization'] = 'Basic '+ encoded_user_pass # Basic 前有空格
		else:
			print('*****ProxyMiddle has pass******')
			request.mata['proxy'] = "http://%s" % proxy['ip_port']
					

类 RandomUseAgent 主要用来动态获取 user agent， user agent 列表， USER_AGENTS 在 settings.py 中进行配置。
类 ProxyMiddleware 用来切换代理， proxy 列表 PROXIES 也是在 settings.py 中进行配置。

2.修改 settings.py 配置 USER_AGENTS 和 PROXIES

添加 USER_AGENT :

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",
]

添加代理 IP 设置 PROXIES :

PROXIES = [
    {'ip_port': '111.11.228.75:80', 'user_pass': ''},
    {'ip_port': '120.198.243.22:80', 'user_pass': ''},
    {'ip_port': '111.8.60.9:8123', 'user_pass': ''},
    {'ip_port': '101.71.27.120:80', 'user_pass': ''},
    {'ip_port': '122.96.59.104:80', 'user_pass': ''},
    {'ip_port': '122.224.249.122:8088', 'user_pass': ''},
]

禁用cookies

COOKIES_ENABLED=False

设置下载延迟

DOWNLOAD_DELAY=3

设置 DOWNLOADER_MIDDLEWARES

DOWNLOADER_MIDDLEWARES = {
     # 'cnblogs.middlewares.MyCustomDownloaderMiddleware': 543,
    'cnblogs.middlewares.RandomUserAgent': 1,
    'scrapy.contrib.downloadermiddleware.httpproxy.HttpProxyMiddleware': 110,
    #'scrapy.downloadermiddlewares.httpproxy.HttpProxyMiddleware': 110,
    'cnblogs.middlewares.ProxyMiddleware': 100,
}