middlewares下载中间件、断点爬取、设置文件参数

User-Agent
Cookies
IP
Selenium

1.User-Agent

settings.py文件中添加几个UA

USERAGENT = [
    'Mozilla/5.0 (X11; U; Linux x86_64; zh-CN; rv:1.9.2.10) Gecko/20100922 Ubuntu/10.10 (maverick) Firefox/3.6.10',
    'Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.11 (KHTML, like Gecko) Chrome/23.0.1271.64 Safari/537.11',
]

middlewares.py中设置User-Agent中间件

从settings.py文件中取值有两种方式
方法一：

class UserAgentDownloadMiddlerware(object):
     def __init__(self,User_Agents):
         self.User_Agents = User_Agents
    
     @classmethod
     def from_crawler(cls,crawler):
         User_Agents = crawler.settings['USERAGENT']
       return cls(User_Agents)
    
    def process_request(self,request,spider):
        """
        所有的request在交给下载器之前都会经过这个方法
        :param request:
        :param spider:
        :return:
        """
        import random
        radom_ua = random.choice(self.User_Agents)
        if random_ua:
            request.headers['User-Agent']=random_ua

方法二：

class UserAgentDownloadMiddlerware(object):
    def process_request(self,request,spider):
         import random
         User_Agent = spider.settings['USERAGENT']
         random_ua = random.choice(User_Agent)
         if random_ua:
            request.headers['User-Agent']=random_ua

方法三：

class UserAgentDownloadMiddlerware(object):
    def process_request(self,request,spider):
    from fake_useragent import UserAgent
        useAgent = UserAgent()
        random_ua = useAgent.random
        if random_ua:
            print('经过了下载中间件',random_ua)
            request.headers['User-Agent'] = random_ua

2.IP代理中间件

在settings.py文件中模拟一个代理池

PROXIES =[
    {'ip':'127.0.0.1:6379','pwd':'zwz:1234'},有账号密码
    {'ip':'127.0.0.1:6372','pwd':None},没有账号密码
    {'ip':'127.0.0.1:6373','pwd':None},
    {'ip':'127.0.0.1:6370','pwd':None}
]

middlewares.py中设置代理中间件

class ProxyDownloadMiddlerware(object):
    def process_request(self,request,spider):
        proxies = spider.settings['PROXIES']
        import random
        proxy_rm = random.choice(proxies)

        if proxy_rm['pwd']:
            #有账号密码的代理
            #对账号密码进行base64编码
            import base64
            base64_pwd = base64.b64encode(proxy_rm['pwd'].encode('utf-8')).decode('utf-8')
            # 对应到代理服务器的信令格式里
            request.headers['Proxy-Authorization'] = 'Basic ' + base64_pwd
            #设置ip
            request.meta['proxy'] = proxy_rm['ip']
        else:
            # 设置ip
            request.meta['proxy'] = proxy_rm['ip']

3.Cookie中间件

在settings.py文件中模拟一个Cookie池

COOKIES =[
    {'cookie1':'xxxx'},
    {'cookie1':'xxxx'},
    {'cookie1':'xxxx'},
    {'cookie1':'xxxx'},
    {'cookie1':'xxxx'},
]

middlewares.py中设置cookie中间件

import random
class RandomCookiesMiddleware(object):

    def process_request(self, request, spider):
        cookies = spider.settings['COOKIES']
        # 随机获取一个cookies
        cookie = random.choice(cookies)
        if cookie:
            request.cookies = cookie

4.Selenium获取动态的网页爬取

在创建的spider项目里添加,因为有的网页是动态的，还有静态的，所以放在需要爬取动态页面的spider里

import scrapy
from selenium import webdriver

class TestSpider(scrapy.Spider):
    name = 'test'
    allowed_domains = ['baidu.com']
    start_urls = ['http://www.baidu.com/']

    # 创建浏览器驱动
    driver = webdriver.Firefox(
        executable_path='/home/zwz/Desktop/浏览器驱动/geckodriver/'
    )
    driver.set_page_load_timeout(10)

    def parse(self, response):
        print(response.status,response.request.headers)

middlewares.py中设置Selenium获取动态的网页爬取

#scrapy并不支持动态加载网页的爬取
from selenium import webdriver
from selenium.common.exceptions import TimeoutException
from scrapy.http import HtmlResponse
class SeleniumDownloadMiddlerWare(object):
    @classmethod
    def from_crawler(cls, crawler):
        # This method is used by Scrapy to create your spiders.
        s = cls()
        #使用信号量,监控爬虫结束的信号
        crawler.signals.connect(s.close, signal=signals.spider_closed)
        return s

    def close(self, spider):
        import time
        time.sleep(5)
        spider.driver.close()

    def process_request(self,request,spider):
        if spider.name == 'test':
            #获取url
            url = request.url

            if url:
                try:
                    # self.driver.get(url)
                    spider.driver.get(url)
                    # pageSource = self.driver.page_source
                    pageSource = spider.driver.page_source

                    if pageSource:
                        """
                        url, status=200, headers=None, 
                        body=b'', flags=None, request=None
                        """
                        return HtmlResponse(
                            url=url,
                            status=200,
                            body=pageSource.encode('utf-8'),
                            request=request
                        )

                except TimeoutException as err:
                    print('请求超时',url)
                    return HtmlResponse(
                        url=url,
                        status=408,
                        body=b'',
                        request=request
                    )

最后别忘记设置和激活下载中间件

在settings.py文件中

DOWNLOADER_MIDDLEWARES = {
   # 'downloadmiddlerware.middlewares.DownloadmiddlerwareDownloaderMiddleware': 543,
    'downloadmiddlerware.middlewares.UserAgentDownloadMiddlerware':543,
    'downloadmiddlerware.middlewares.ProxyDownloadMiddlerware':544,
    'downloadmiddlerware.middlewares.RandomCookiesMiddleware':545,
    'downloadmiddlerware.middlewares.SeleniumDownloadMiddlerWare':546,
}

关于爬虫的断点爬取：

scrapy crawl 爬虫名称 -s JOBDIR=crawls/爬虫名称

requests.queue : 保存的请求的任务队列
requests.seen : 保存的是指纹
spider.status : 爬虫运行的状态

scrapy settings.py设置文件（相关参数）

项目名称

BOT_NAME = 'downloadmiddlerware'

# 项目名称
BOT_NAME = 'downloadmiddlerware'

#爬虫存储的文件路径
SPIDER_MODULES = ['downloadmiddlerware.spiders']
#创建爬虫文件的模版,创建号的爬虫文件会存放在这个目录下
NEWSPIDER_MODULE = 'downloadmiddlerware.spiders'

# Crawl responsibly by identifying yourself (and your website) on the user-agent
#设置ua,来模拟浏览器请求
#USER_AGENT = 'downloadmiddlerware (+http://www.yourdomain.com)'

# Obey robots.txt rules
# 设置是否需要准守robot协议:默认为True
ROBOTSTXT_OBEY = False

# Configure maximum concurrent requests performed by Scrapy (default: 16)
# 设置请求的最大并发数据(下载器)　默认是16
#CONCURRENT_REQUESTS = 32

# Configure a delay for requests for the same website (default: 0)
# See https://doc.scrapy.org/en/latest/topics/settings.html#download-delay
# See also autothrottle settings and docs
#设置请求的下载延时,默认为0
DOWNLOAD_DELAY = 3
# The download delay setting will honor only one of:
#设置网站的最大并发请求数量,默认是8
CONCURRENT_REQUESTS_PER_DOMAIN = 16

#设置某个ip的最大并发请求数量,默认是0
# 如果非0
# 1.CONCURRENT_REQUESTS_PER_DOMAIN不生效,
# 这时候请求的并发数量将针对于ip,而不是网站了
#
# 2.设置的DOWNLOAD_DELAY就是正对于ip而不是网站了
CONCURRENT_REQUESTS_PER_IP = 16

# Disable cookies (enabled by default)
# 是否携带cookies:默认为True
COOKIES_ENABLED = False

#COOKIES_DEBUG:跟踪cookies,默认情况下为False
COOKIES_DEBUG =True

#关于日志信息的设置
LOG_FILE = 'xxx.log'
LOG_LEVEL = 'INFO/DEBUG/....'

# Disable Telnet Console (enabled by default)
#是一个终端的扩展插件
TELNETCONSOLE_ENABLED = False

# Override the default request headers:
#设置默认的请求头(cookies信息不要放在这里)
DEFAULT_REQUEST_HEADERS = {
  # 'Accept': 'text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8',
  # 'Accept-Language': 'en',
    'User-Agent':'Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/68.0.3440.106 Safari/537.36',
}

# Enable or disable spider middlewares
# See https://doc.scrapy.org/en/latest/topics/spider-middleware.html
#设置和激活爬虫中间件
#SPIDER_MIDDLEWARES = {
#    'downloadmiddlerware.middlewares.DownloadmiddlerwareSpiderMiddleware': 543,
#}

# Enable or disable downloader middlewares
# See https://doc.scrapy.org/en/latest/topics/downloader-middleware.html
#设置和激活下载中间件（后面的数字表示优先级）
DOWNLOADER_MIDDLEWARES = {
   # 'downloadmiddlerware.middlewares.DownloadmiddlerwareDownloaderMiddleware': 543,
   #  'downloadmiddlerware.middlewares.UserAgentDownloadMiddlerware':543,
    'downloadmiddlerware.middlewares.SeleniumDownloadMiddlerWare':543,
}

# Enable or disable extensions
# See https://doc.scrapy.org/en/latest/topics/extensions.html
#设置扩展
EXTENSIONS = {
   'scrapy.extensions.telnet.TelnetConsole': None,
}

# Configure item pipelines
# See https://doc.scrapy.org/en/latest/topics/item-pipeline.html
#设置和激活管道文件（后面的数字表示优先级）
ITEM_PIPELINES = {
    'downloadmiddlerware.pipelines.DownloadmiddlerwarePipeline': 300,
}

#自动限速的扩展（实现上一个请求和下一个请求之间的时间是不固定的）
# Enable and configure the AutoThrottle extension (disabled by default)
# See https://doc.scrapy.org/en/latest/topics/autothrottle.html
#默认请情框下自动限速的扩展是关闭的：AUTOTHROTTLE_ENABLED：False
 AUTOTHROTTLE_ENABLED = True
 # The initial download delay
 #初始的下载吧延时默认是5秒
 AUTOTHROTTLE_START_DELAY = 5
 # The maximum download delay to be set in case of high latencies
 #最大下载延时
 AUTOTHROTTLE_MAX_DELAY = 60
 # The average number of requests Scrapy should be sending in parallel to
 # each remote server
 #针对于网站的最大的并行请求数量
 AUTOTHROTTLE_TARGET_CONCURRENCY = 1.0
 # Enable showing throttling stats for every response received:
#调试模式:默认为False,未开启
AUTOTHROTTLE_DEBUG = False

# Enable and configure HTTP caching (disabled by default)
# See https://doc.scrapy.org/en/latest/topics/downloader-middleware.html#httpcache-middleware-settings
#设置数据的缓存,默认情况下是未开启的
HTTPCACHE_ENABLED = True
#设置缓存的超时时间,默认为0表示永久有效
HTTPCACHE_EXPIRATION_SECS = 0
#设置缓存的存储文件路径
HTTPCACHE_DIR = 'httpcache'
#忽略某些状态码的请求结果(Response)
HTTPCACHE_IGNORE_HTTP_CODES = []
#开始缓存的扩展插件
HTTPCACHE_STORAGE = 'scrapy.extensions.httpcache.FilesystemCacheStorage'