python爬虫--分布式爬虫

Scrapy-Redis分布式爬虫

介绍

scrapy-redis巧妙的利用redis 实现 request queue和 items queue，利用redis的set实现request的去重，将scrapy从单台机器扩展多台机器，实现较大规模的爬虫集群

scrapy-redis是基于redis的scrapy组件
• 分布式爬虫
	多个爬虫实例分享一个redis request队列，非常适合大范围多域名的爬虫集群
• 分布式后处理
	爬虫抓取到的items push到一个redis items队列,这就意味着可以开启多个items processes来处理抓取到的数据，比如存储到Mongodb、Mysql
• 基于scrapy即插即用组件
	Scheduler + Duplication Filter, Item Pipeline, Base Spiders.

scrapy-redis架构

• 调度器(Scheduler)

scrapy-redis调度器通过redis的set不重复的特性，实现了Duplication Filter去重（DupeFilter set存放爬取过的request）。
Spider新生成的request，将request的指纹到redis的DupeFilter set检查是否重复，并将不重复的request push写入redis的request队列。
调度器每次从redis的request队列里根据优先级pop出一个request, 将此request发给spider处理。

• Item Pipeline

将Spider爬取到的Item给scrapy-redis的Item Pipeline，将爬取到的Item存入redis的items队列。可以很方便的从items队列中提取item，从而实现items processes 集群

scrapy - redis安装与使用

安装scrapy-redis

之前已经装过scrapy了，这里直接装scrapy-redis

pip install scrapy-redis

使用scrapy-redis的example来修改

先从github上拿到scrapy-redis的example，然后将里面的example-project目录移到指定的地址

git clone https://github.com/rolando/scrapy-redis.git
cp -r scrapy-redis/example-project ./scrapy-youyuan

或者将整个项目下载回来scrapy-redis-master.zip解压后

cp -r scrapy-redis-master/example-project/ ./redis-youyuan
cd redis-youyuan/

tree查看项目目录

修改settings.py

注意：settings里面的中文注释会报错，换成英文

# 指定使用scrapy-redis的Scheduler
SCHEDULER = "scrapy_redis.scheduler.Scheduler"
# 在redis中保持scrapy-redis用到的各个队列，从而允许暂停和暂停后恢复
SCHEDULER_PERSIST = True
# 指定排序爬取地址时使用的队列，默认是按照优先级排序
SCHEDULER_QUEUE_CLASS = 'scrapy_redis.queue.SpiderPriorityQueue'
# 可选的先进先出排序
# SCHEDULER_QUEUE_CLASS = 'scrapy_redis.queue.SpiderQueue'
# 可选的后进先出排序
# SCHEDULER_QUEUE_CLASS = 'scrapy_redis.queue.SpiderStack'
# 只在使用SpiderQueue或者SpiderStack是有效的参数,，指定爬虫关闭的最大空闲时间
SCHEDULER_IDLE_BEFORE_CLOSE = 10
# 指定RedisPipeline用以在redis中保存item
ITEM_PIPELINES = {
    'example.pipelines.ExamplePipeline': 300,
    'scrapy_redis.pipelines.RedisPipeline': 400
}
# 指定redis的连接参数
# REDIS_PASS是我自己加上的redis连接密码，需要简单修改scrapy-redis的源代码以支持使用密码连接redis
REDIS_HOST = '127.0.0.1'
REDIS_PORT = 6379
# Custom redis client parameters (i.e.: socket timeout, etc.)
REDIS_PARAMS  = {}
#REDIS_URL = 'redis://user:pass@hostname:9001'
#REDIS_PARAMS['password'] = 'itcast.cn'
LOG_LEVEL = 'DEBUG'
DUPEFILTER_CLASS = 'scrapy.dupefilters.RFPDupeFilter'
#The class used to detect and filter duplicate requests.
#The default (RFPDupeFilter) filters based on request fingerprint using the scrapy.utils.request.request_fingerprint function. In order to change the way duplicates are checked you could subclass RFPDupeFilter and override its request_fingerprint method. This method should accept scrapy Request object and return its fingerprint (a string).
#By default, RFPDupeFilter only logs the first duplicate request. Setting DUPEFILTER_DEBUG to True will make it log all duplicate requests.
DUPEFILTER_DEBUG =True
# Override the default request headers:
DEFAULT_REQUEST_HEADERS = {
    'Accept': 'text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8',
    'Accept-Language': 'zh-CN,zh;q=0.8',
    'Connection': 'keep-alive',
    'Accept-Encoding': 'gzip, deflate, sdch',
}

查看pipeline.py

from datetime import datetime
class ExamplePipeline(object):
    def process_item(self, item, spider):
        item["crawled"] = datetime.utcnow()
        item["spider"] = spider.name
        return item

流程

    - 概念：可以使用多台电脑组件一个分布式机群，让其执行同一组程序，对同一组网络资源进行联合爬取。
    - 原生的scrapy是无法实现分布式
        - 调度器无法被共享
        - 管道无法被共享
    - 基于scrapy+redis（scrapy&scrapy-redis组件）实现分布式
    - scrapy-redis组件作用：
        - 提供可被共享的管道和调度器
    - 环境安装：
        - pip install scrapy-redis
    - 编码流程：
        1.创建工程
        2.cd proName
        3.创建crawlspider的爬虫文件
        4.修改一下爬虫类：
            - 导包：from scrapy_redis.spiders import RedisCrawlSpider
            - 修改当前爬虫类的父类：RedisCrawlSpider
            - allowed_domains和start_urls删除
            - 添加一个新属性：redis_key = 'xxxx'可以被共享的调度器队列的名称
        5.修改配置settings.py
            - 指定管道
                ITEM_PIPELINES = {
                        'scrapy_redis.pipelines.RedisPipeline': 400
                    }
            - 指定调度器
                # 增加了一个去重容器类的配置, 作用使用Redis的set集合来存储请求的指纹数据, 从而实现请求去重的持久化
                DUPEFILTER_CLASS = "scrapy_redis.dupefilter.RFPDupeFilter"
                # 使用scrapy-redis组件自己的调度器
                SCHEDULER = "scrapy_redis.scheduler.Scheduler"
                # 配置调度器是否要持久化, 也就是当爬虫结束了, 要不要清空Redis中请求队列和去重指纹的set。如果是True, 就表示要持久化存储, 就不清空数据, 否则清空数据
                SCHEDULER_PERSIST = True
            - 指定redis数据库
                REDIS_HOST = 'redis服务的ip地址'
                REDIS_PORT = 6379
         6.配置redis数据库（redis.windows.conf）
            - 关闭默认绑定
                - 56Line：#bind 127.0.0.1
            - 关闭保护模式
                - 75line：protected-mode no
         7.启动redis服务（携带配置文件）和客户端
            - redis-server.exe redis.windows.conf
            - redis-cli
         8.执行工程
            - scrapy runspider spider.py
         9.将起始的url仍入到可以被共享的调度器的队列（sun）中
            - 在redis-cli中操作：lpush sun www.xxx.com
         10.redis:
            - xxx:items:存储的就是爬取到的数据

分布式爬取案例

爬虫程序

# -*- coding: utf-8 -*-
import scrapy
from scrapy.linkextractors import LinkExtractor
from scrapy.spiders import CrawlSpider, Rule
from scrapy_redis.spiders import RedisCrawlSpider
from fbs.items import FbsproItem
class FbsSpider(RedisCrawlSpider):
    name = 'fbs_obj'
    # allowed_domains = ['www.xxx.com']
    # start_urls = ['http://www.xxx.com/']
    redis_key = 'sun'#可以被共享的调度器队列的名称
    link = LinkExtractor(allow=r'type=4&page=\d+')
    rules = (
        Rule(link, callback='parse_item', follow=True),
    )
    print(123)
    def parse_item(self, response):
        tr_list = response.xpath('//*[@id="morelist"]/div/table[2]//tr/td/table//tr')
        for tr in tr_list:
            title = tr.xpath('./td[2]/a[2]/@title').extract_first()
            status = tr.xpath('./td[3]/span/text()').extract_first()
            item = FbsproItem()
            item['title'] = title
            item['status'] = status
            print(title)
            yield item

settings.py

# -*- coding: utf-8 -*-
# Scrapy settings for fbsPro project
#
# For simplicity, this file contains only settings considered important or
# commonly used. You can find more settings consulting the documentation:
#
#     https://docs.scrapy.org/en/latest/topics/settings.html
#     https://docs.scrapy.org/en/latest/topics/downloader-middleware.html
#     https://docs.scrapy.org/en/latest/topics/spider-middleware.html
BOT_NAME = 'fbs_obj'
SPIDER_MODULES = ['fbs_obj.spiders']
NEWSPIDER_MODULE = 'fbs_obj.spiders'
# Crawl responsibly by identifying yourself (and your website) on the user-agent
#USER_AGENT = 'fbsPro (+http://www.yourdomain.com)'
USER_AGENT = 'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/78.0.3904.97 Safari/537.36'
# Obey robots.txt rules
ROBOTSTXT_OBEY = False
# Configure maximum concurrent requests performed by Scrapy (default: 16)
CONCURRENT_REQUESTS = 2
# Configure a delay for requests for the same website (default: 0)
# See https://docs.scrapy.org/en/latest/topics/settings.html#download-delay
# See also autothrottle settings and docs
#DOWNLOAD_DELAY = 3
# The download delay setting will honor only one of:
#CONCURRENT_REQUESTS_PER_DOMAIN = 16
#CONCURRENT_REQUESTS_PER_IP = 16
# Disable cookies (enabled by default)
#COOKIES_ENABLED = False
# Disable Telnet Console (enabled by default)
#TELNETCONSOLE_ENABLED = False
# Override the default request headers:
#DEFAULT_REQUEST_HEADERS = {
#   'Accept': 'text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8',
#   'Accept-Language': 'en',
#}
# Enable or disable spider middlewares
# See https://docs.scrapy.org/en/latest/topics/spider-middleware.html
#SPIDER_MIDDLEWARES = {
#    'fbsPro.middlewares.FbsproSpiderMiddleware': 543,
#}
# Enable or disable downloader middlewares
# See https://docs.scrapy.org/en/latest/topics/downloader-middleware.html
#DOWNLOADER_MIDDLEWARES = {
#    'fbsPro.middlewares.FbsproDownloaderMiddleware': 543,
#}
# Enable or disable extensions
# See https://docs.scrapy.org/en/latest/topics/extensions.html
#EXTENSIONS = {
#    'scrapy.extensions.telnet.TelnetConsole': None,
#}
# Configure item pipelines
# See https://docs.scrapy.org/en/latest/topics/item-pipeline.html
#ITEM_PIPELINES = {
#    'fbsPro.pipelines.FbsproPipeline': 300,
#}
# Enable and configure the AutoThrottle extension (disabled by default)
# See https://docs.scrapy.org/en/latest/topics/autothrottle.html
#AUTOTHROTTLE_ENABLED = True
# The initial download delay
#AUTOTHROTTLE_START_DELAY = 5
# The maximum download delay to be set in case of high latencies
#AUTOTHROTTLE_MAX_DELAY = 60
# The average number of requests Scrapy should be sending in parallel to
# each remote server
#AUTOTHROTTLE_TARGET_CONCURRENCY = 1.0
# Enable showing throttling stats for every response received:
#AUTOTHROTTLE_DEBUG = False
# Enable and configure HTTP caching (disabled by default)
# See https://docs.scrapy.org/en/latest/topics/downloader-middleware.html#httpcache-middleware-settings
#HTTPCACHE_ENABLED = True
#HTTPCACHE_EXPIRATION_SECS = 0
#HTTPCACHE_DIR = 'httpcache'
#HTTPCACHE_IGNORE_HTTP_CODES = []
#HTTPCACHE_STORAGE = 'scrapy.extensions.httpcache.FilesystemCacheStorage'
#指定管道
ITEM_PIPELINES = {
    'scrapy_redis.pipelines.RedisPipeline': 400
}
#指定调度器
# 增加了一个去重容器类的配置, 作用使用Redis的set集合来存储请求的指纹数据, 从而实现请求去重的持久化
DUPEFILTER_CLASS = "scrapy_redis.dupefilter.RFPDupeFilter"
# 使用scrapy-redis组件自己的调度器
SCHEDULER = "scrapy_redis.scheduler.Scheduler"
# 配置调度器是否要持久化, 也就是当爬虫结束了, 要不要清空Redis中请求队列和去重指纹的set。如果是True, 就表示要持久化存储, 就不清空数据, 否则清空数据
SCHEDULER_PERSIST = True
#指定redis
REDIS_HOST = '192.168.16.119'
REDIS_PORT = 6379

item.py

import scrapy
class FbsproItem(scrapy.Item):
    # define the fields for your item here like:
    title = scrapy.Field()
    status = scrapy.Field()