Scrapy-Redis结合POST请求获取数据的方法示例

前言

通常我们在一个站站点进行采集的时候，如果是小站的话 我们使用scrapy本身就可以满足。

但是如果在面对一些比较大型的站点的时候，单个scrapy就显得力不从心了。

要是我们能够多个Scrapy一起采集该多好啊 人多力量大。

很遗憾Scrapy官方并不支持多个同时采集一个站点，虽然官方给出一个方法：

**将一个站点的分割成几部分 交给不同的scrapy去采集**

似乎是个解决办法，但是很麻烦诶！毕竟分割很麻烦的哇

下面就改轮到我们的额主角Scrapy-Redis登场了！

能看到这篇文章的小伙伴肯定已经知道什么是Scrapy以及Scrapy-Redis了，基础概念这里就不再介绍。默认情况下Scrapy-Redis是发送GET请求获取数据的，对于某些使用POST请求的情况需要重写make_request_from_data函数即可，但奇怪的是居然没在网上搜到简洁明了的答案，或许是太简单了？。

这里我以httpbin.org这个网站为例，首先在settings.py中添加所需配置，这里需要根据实际情况进行修改：

SCHEDULER = "scrapy_redis.scheduler.Scheduler" #启用Redis调度存储请求队列
SCHEDULER_PERSIST = True #不清除Redis队列、这样可以暂停/恢复 爬取
DUPEFILTER_CLASS = "scrapy_redis.dupefilter.RFPDupeFilter" #确保所有的爬虫通过Redis去重
SCHEDULER_QUEUE_CLASS = 'scrapy_redis.queue.SpiderPriorityQueue'
REDIS_URL = "redis://127.0.0.1:6379"

爬虫代码如下：

# -*- coding: utf-8 -*-
import scrapy
from scrapy_redis.spiders import RedisSpider


class HpbSpider(RedisSpider):
 name = 'hpb'
 redis_key = 'test_post_data'

 def make_request_from_data(self, data):
  """Returns a Request instance from data coming from Redis.
  By default, ``data`` is an encoded URL. You can override this method to
  provide your own message decoding.
  Parameters
  ----------
  data : bytes
   Message from redis.
  """
  return scrapy.FormRequest("https://www.httpbin.org/post",
         formdata={"data":data},callback=self.parse)

 def parse(self, response):
  print(response.body)

这里为了简单直接进行输出，真实使用时可以结合pipeline写数据库等。

然后启动爬虫程序scrapy crawl hpb，由于我们还没向test_post_data中写数据，所以启动后程序进入等待状态。然后模拟向队列写数据：

import redis
rd = redis.Redis('127.0.0.1',port=6379,db=0)
for _ in range(1000):
 rd.lpush('test_post_data',_)

此时可以看到爬虫已经开始获取程序了：

2019-05-06 16:30:21 [hpb] DEBUG: Read 8 requests from 'test_post_data'
2019-05-06 16:30:21 [scrapy.core.engine] DEBUG: Crawled (200) <POST https://www.httpbin.org/post> (referer: None)
2019-05-06 16:30:21 [scrapy.core.engine] DEBUG: Crawled (200) <POST https://www.httpbin.org/post> (referer: None)
2019-05-06 16:30:21 [scrapy.core.engine] DEBUG: Crawled (200) <POST https://www.httpbin.org/post> (referer: None)
2019-05-06 16:30:21 [scrapy.core.engine] DEBUG: Crawled (200) <POST https://www.httpbin.org/post> (referer: None)
2019-05-06 16:30:21 [scrapy.core.engine] DEBUG: Crawled (200) <POST https://www.httpbin.org/post> (referer: None)
2019-05-06 16:30:21 [scrapy.core.engine] DEBUG: Crawled (200) <POST https://www.httpbin.org/post> (referer: None)
2019-05-06 16:30:21 [scrapy.core.engine] DEBUG: Crawled (200) <POST https://www.httpbin.org/post> (referer: None)
2019-05-06 16:30:21 [scrapy.core.engine] DEBUG: Crawled (200) <POST https://www.httpbin.org/post> (referer: None)
b'{\n  "args": {}, \n  "data": "", \n  "files": {}, \n  "form": {\n    "data": "0"\n  }, \n  "headers": {\n    "Accept": "text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8", \n    "Accept-Encoding": "gzip,deflate", \n    "Accept-Language": "en", \n    "Content-Length": "6", \n    "Content-Type": "application/x-www-form-urlencoded", \n    "Host": "www.httpbin.org", \n    "User-Agent": "Scrapy/1.5.1 (+https://scrapy.org)"\n  }, \n  "json": null, \n  "origin": "1.2.3.48, 1.2.3.48", \n  "url": "https://www.httpbin.org/post"\n}\n'
b'{\n  "args": {}, \n  "data": "", \n  "files": {}, \n  "form": {\n    "data": "1"\n  }, \n  "headers": {\n    "Accept": "text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8", \n    "Accept-Encoding": "gzip,deflate", \n    "Accept-Language": "en", \n    "Content-Length": "6", \n    "Content-Type": "application/x-www-form-urlencoded", \n    "Host": "www.httpbin.org", \n    "User-Agent": "Scrapy/1.5.1 (+https://scrapy.org)"\n  }, \n  "json": null, \n  "origin": "1.2.3.48, 1.2.3.48", \n  "url": "https://www.httpbin.org/post"\n}\n'
b'{\n  "args": {}, \n  "data": "", \n  "files": {}, \n  "form": {\n    "data": "3"\n  }, \n  "headers": {\n    "Accept": "text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8", \n    "Accept-Encoding": "gzip,deflate", \n    "Accept-Language": "en", \n    "Content-Length": "6", \n    "Content-Type": "application/x-www-form-urlencoded", \n    "Host": "www.httpbin.org", \n    "User-Agent": "Scrapy/1.5.1 (+https://scrapy.org)"\n  }, \n  "json": null, \n  "origin": "1.2.3.48, 1.2.3.48", \n  "url": "https://www.httpbin.org/post"\n}\n'
b'{\n  "args": {}, \n  "data": "", \n  "files": {}, \n  "form": {\n    "data": "2"\n  }, \n  "headers": {\n    "Accept": "text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8", \n    "Accept-Encoding": "gzip,deflate", \n    "Accept-Language": "en", \n    "Content-Length": "6", \n    "Content-Type": "application/x-www-form-urlencoded", \n    "Host": "www.httpbin.org", \n    "User-Agent": "Scrapy/1.5.1 (+https://scrapy.org)"\n  }, \n  "json": null, \n  "origin": "1.2.3.48, 1.2.3.48", \n  "url": "https://www.httpbin.org/post"\n}\n'
b'{\n  "args": {}, \n  "data": "", \n  "files": {}, \n  "form": {\n    "data": "4"\n  }, \n  "headers": {\n    "Accept": "text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8", \n    "Accept-Encoding": "gzip,deflate", \n    "Accept-Language": "en", \n    "Content-Length": "6", \n    "Content-Type": "application/x-www-form-urlencoded", \n    "Host": "www.httpbin.org", \n    "User-Agent": "Scrapy/1.5.1 (+https://scrapy.org)"\n  }, \n  "json": null, \n  "origin": "1.2.3.48, 1.2.3.48", \n  "url": "https://www.httpbin.org/post"\n}\n'
b'{\n  "args": {}, \n  "data": "", \n  "files": {}, \n  "form": {\n    "data": "5"\n  }, \n  "headers": {\n    "Accept": "text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8", \n    "Accept-Encoding": "gzip,deflate", \n    "Accept-Language": "en", \n    "Content-Length": "6", \n    "Content-Type": "application/x-www-form-urlencoded", \n    "Host": "www.httpbin.org", \n    "User-Agent": "Scrapy/1.5.1 (+https://scrapy.org)"\n  }, \n  "json": null, \n  "origin": "1.2.3.48, 1.2.3.48", \n  "url": "https://www.httpbin.org/post"\n}\n'
b'{\n  "args": {}, \n  "data": "", \n  "files": {}, \n  "form": {\n    "data": "6"\n  }, \n  "headers": {\n    "Accept": "text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8", \n    "Accept-Encoding": "gzip,deflate", \n    "Accept-Language": "en", \n    "Content-Length": "6", \n    "Content-Type": "application/x-www-form-urlencoded", \n    "Host": "www.httpbin.org", \n    "User-Agent": "Scrapy/1.5.1 (+https://scrapy.org)"\n  }, \n  "json": null, \n  "origin": "1.2.3.48, 1.2.3.48", \n  "url": "https://www.httpbin.org/post"\n}\n'
b'{\n  "args": {}, \n  "data": "", \n  "files": {}, \n  "form": {\n    "data": "7"\n  }, \n  "headers": {\n    "Accept": "text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8", \n    "Accept-Encoding": "gzip,deflate", \n    "Accept-Language": "en", \n    "Content-Length": "6", \n    "Content-Type": "application/x-www-form-urlencoded", \n    "Host": "www.httpbin.org", \n    "User-Agent": "Scrapy/1.5.1 (+https://scrapy.org)"\n  }, \n  "json": null, \n  "origin": "1.2.3.48, 1.2.3.48", \n  "url": "https://www.httpbin.org/post"\n}\n'
2019-05-06 16:31:09 [scrapy.extensions.logstats] INFO: Crawled 1001 pages (at 280 pages/min), scraped 0 items (at 0 items/min)
2019-05-06 16:32:09 [scrapy.extensions.logstats] INFO: Crawled 1001 pages (at 0 pages/min), scraped 0 items (at 0 items/min)
2019-05-06 16:33:09 [scrapy.extensions.logstats] INFO: Crawled 1001 pages (at 0 pages/min), scraped 0 items (at 0 items/min)

至于数据重复的问题，如果POST的数据重复，这个请求就不会发送出去。如果有特殊情况POST发送同样的数据回得到不同返回值，添加dont_filter=True是没用的，在RFPDupeFilter类中并没考虑这个参数，需要重写。

总结