Scrapy-Redis结合POST请求获取数据

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。

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