scrapy-redis使用以及剖析(转)

scrapy-redis是一个基于redis的scrapy组件，通过它可以快速实现简单分布式爬虫程序，该组件本质上提供了三大功能：

scheduler - 调度器
dupefilter - URL去重规则（被调度器使用）
pipeline - 数据持久化

scrapy-redis组件

1. URL去重

定义去重规则（被调度器调用并应用）

a. 内部会使用以下配置进行连接Redis

# REDIS_HOST = 'localhost' # 主机名

# REDIS_PORT = 6379 # 端口

# REDIS_URL = 'redis://user:pass@hostname:9001' # 连接URL（优先于以上配置）

# REDIS_PARAMS  = {}                                  # Redis连接参数             默认：REDIS_PARAMS = {'socket_timeout': 30,'socket_connect_timeout': 30,'retry_on_timeout': True,'encoding': REDIS_ENCODING,}）

# REDIS_PARAMS['redis_cls'] = 'myproject.RedisClient' # 指定连接Redis的Python模块默认：redis.StrictRedis

# REDIS_ENCODING = "utf-8"                            # redis编码类型             默认：'utf-8'

b. 去重规则通过redis的集合完成，集合的Key为：

key = defaults.DUPEFILTER_KEY % {'timestamp': int(time.time())}

默认配置：

DUPEFILTER_KEY = 'dupefilter:%(timestamp)s'

c. 去重规则中将url转换成唯一标示，然后在redis中检查是否已经在集合中存在

from scrapy.utils import request

from scrapy.http import Request

req = Request(url='http://www.cnblogs.com/wupeiqi.html')

result = request.request_fingerprint(req)

print(result) # 8ea4fd67887449313ccc12e5b6b92510cc53675c

PS:

- URL参数位置不同时，计算结果一致；

- 默认请求头不在计算范围，include_headers可以设置指定请求头

示例：

from scrapy.utils import request

from scrapy.http import Request

req = Request(url='http://www.baidu.com?name=8&id=1',callback=lambda x:print(x),cookies={'k1':'vvvvv'})

result = request.request_fingerprint(req,include_headers=['cookies',])

print(result)

req = Request(url='http://www.baidu.com?id=1&name=8',callback=lambda x:print(x),cookies={'k1':666})

result = request.request_fingerprint(req,include_headers=['cookies',])

print(result)

"""

# Ensure all spiders share same duplicates filter through redis.

# DUPEFILTER_CLASS = "scrapy_redis.dupefilter.RFPDupeFilter"

2. 调度器

"""

调度器，调度器使用PriorityQueue（有序集合）、FifoQueue（列表）、LifoQueue（列表）进行保存请求，并且使用RFPDupeFilter对URL去重

a. 调度器

SCHEDULER_QUEUE_CLASS = 'scrapy_redis.queue.PriorityQueue'          # 默认使用优先级队列（默认），其他：PriorityQueue（有序集合），FifoQueue（列表）、LifoQueue（列表）

SCHEDULER_QUEUE_KEY = '%(spider)s:requests'                         # 调度器中请求存放在redis中的key

SCHEDULER_SERIALIZER = "scrapy_redis.picklecompat"                  # 对保存到redis中的数据进行序列化，默认使用pickle

SCHEDULER_PERSIST = True                                            # 是否在关闭时候保留原来的调度器和去重记录，True=保留，False=清空

SCHEDULER_FLUSH_ON_START = True                                     # 是否在开始之前清空 调度器和去重记录，True=清空，False=不清空

SCHEDULER_IDLE_BEFORE_CLOSE = 10                                    # 去调度器中获取数据时，如果为空，最多等待时间（最后没数据，未获取到）。

SCHEDULER_DUPEFILTER_KEY = '%(spider)s:dupefilter'                  # 去重规则，在redis中保存时对应的key

SCHEDULER_DUPEFILTER_CLASS = 'scrapy_redis.dupefilter.RFPDupeFilter'# 去重规则对应处理的类

"""

# Enables scheduling storing requests queue in redis.

SCHEDULER = "scrapy_redis.scheduler.Scheduler"

# Default requests serializer is pickle, but it can be changed to any module

# with loads and dumps functions. Note that pickle is not compatible between

# python versions.

# Caveat: In python 3.x, the serializer must return strings keys and support

# bytes as values. Because of this reason the json or msgpack module will not

# work by default. In python 2.x there is no such issue and you can use

# 'json' or 'msgpack' as serializers.

# SCHEDULER_SERIALIZER = "scrapy_redis.picklecompat"

# Don't cleanup redis queues, allows to pause/resume crawls.

# SCHEDULER_PERSIST = True

# Schedule requests using a priority queue. (default)

# SCHEDULER_QUEUE_CLASS = 'scrapy_redis.queue.PriorityQueue'

# Alternative queues.

# SCHEDULER_QUEUE_CLASS = 'scrapy_redis.queue.FifoQueue'

# SCHEDULER_QUEUE_CLASS = 'scrapy_redis.queue.LifoQueue'

# Max idle time to prevent the spider from being closed when distributed crawling.

# This only works if queue class is SpiderQueue or SpiderStack,

# and may also block the same time when your spider start at the first time (because the queue is empty).

# SCHEDULER_IDLE_BEFORE_CLOSE = 10　　

3. 数据持久化

2. 定义持久化，爬虫yield Item对象时执行RedisPipeline

a. 将item持久化到redis时，指定key和序列化函数

REDIS_ITEMS_KEY = '%(spider)s:items'

REDIS_ITEMS_SERIALIZER = 'json.dumps'

b. 使用列表保存item数据

4. 起始URL相关

"""

起始URL相关

a. 获取起始URL时，去集合中获取还是去列表中获取？True，集合；False，列表

REDIS_START_URLS_AS_SET = False    # 获取起始URL时，如果为True，则使用self.server.spop；如果为False，则使用self.server.lpop

b. 编写爬虫时，起始URL从redis的Key中获取

REDIS_START_URLS_KEY = '%(name)s:start_urls'

"""

# If True, it uses redis' ``spop`` operation. This could be useful if you

# want to avoid duplicates in your start urls list. In this cases, urls must

# be added via ``sadd`` command or you will get a type error from redis.

# REDIS_START_URLS_AS_SET = False

# Default start urls key for RedisSpider and RedisCrawlSpider.

# REDIS_START_URLS_KEY = '%(name)s:start_urls'

scrapy-redis示例

配置文件

# DUPEFILTER_CLASS = "scrapy_redis.dupefilter.RFPDupeFilter"

#

#

# from scrapy_redis.scheduler import Scheduler

# from scrapy_redis.queue import PriorityQueue

# SCHEDULER = "scrapy_redis.scheduler.Scheduler"

# SCHEDULER_QUEUE_CLASS = 'scrapy_redis.queue.PriorityQueue'          # 默认使用优先级队列（默认），其他：PriorityQueue（有序集合），FifoQueue（列表）、LifoQueue（列表）

# SCHEDULER_QUEUE_KEY = '%(spider)s:requests'                         # 调度器中请求存放在redis中的key

# SCHEDULER_SERIALIZER = "scrapy_redis.picklecompat"                  # 对保存到redis中的数据进行序列化，默认使用pickle

# SCHEDULER_PERSIST = True                                            # 是否在关闭时候保留原来的调度器和去重记录，True=保留，False=清空

# SCHEDULER_FLUSH_ON_START = False                                    # 是否在开始之前清空 调度器和去重记录，True=清空，False=不清空

# SCHEDULER_IDLE_BEFORE_CLOSE = 10                                    # 去调度器中获取数据时，如果为空，最多等待时间（最后没数据，未获取到）。

# SCHEDULER_DUPEFILTER_KEY = '%(spider)s:dupefilter'                  # 去重规则，在redis中保存时对应的key

# SCHEDULER_DUPEFILTER_CLASS = 'scrapy_redis.dupefilter.RFPDupeFilter'# 去重规则对应处理的类

#

#

#

# REDIS_HOST = '10.211.55.13'                           # 主机名

# REDIS_PORT = 6379                                     # 端口

# # REDIS_URL = 'redis://user:pass@hostname:9001'       # 连接URL（优先于以上配置）

# # REDIS_PARAMS  = {}                                  # Redis连接参数             默认：REDIS_PARAMS = {'socket_timeout': 30,'socket_connect_timeout': 30,'retry_on_timeout': True,'encoding': REDIS_ENCODING,}）

# # REDIS_PARAMS['redis_cls'] = 'myproject.RedisClient' # 指定连接Redis的Python模块  默认：redis.StrictRedis

# REDIS_ENCODING = "utf-8"                              # redis编码类型             默认：'utf-8'

配置文件

import scrapy

class ChoutiSpider(scrapy.Spider):

    name = "chouti"

    allowed_domains = ["chouti.com"]

    start_urls = (

        'http://www.chouti.com/',

    )

    def parse(self, response):

        for i in range(0,10):

            yield

爬虫文件

转自：https://www.cnblogs.com/wupeiqi/articles/6912807.html