scrapy-redis使用以及剖析

 1 定义去重规则（被调度器调用并应用）
 2  
 3     a. 内部会使用以下配置进行连接Redis
 4  
 5         # REDIS_HOST = ‘localhost‘                            # 主机名
 6         # REDIS_PORT = 6379                                   # 端口
 7         # REDIS_URL = ‘redis://user:pass@hostname:9001‘       # 连接URL（优先于以上配置）
 8         # 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,}）
 9         # REDIS_PARAMS[‘redis_cls‘] = ‘myproject.RedisClient‘ # 指定连接Redis的Python模块  默认：redis.StrictRedis
10         # REDIS_ENCODING = "utf-8"                            # redis编码类型             默认：‘utf-8‘
11      
12     b. 去重规则通过redis的集合完成，集合的Key为：
13      
14         key = defaults.DUPEFILTER_KEY % {‘timestamp‘: int(time.time())}
15         默认配置：
16             DUPEFILTER_KEY = ‘dupefilter:%(timestamp)s‘
17               
18     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
19      
20         from scrapy.utils import request
21         from scrapy.http import Request
22          
23         req = Request(url=‘http://www.cnblogs.com/wupeiqi.html‘)
24         result = request.request_fingerprint(req)
25         print(result) # 8ea4fd67887449313ccc12e5b6b92510cc53675c
26          
27          
28         PS:
29             - URL参数位置不同时，计算结果一致；
30             - 默认请求头不在计算范围，include_headers可以设置指定请求头
31             示例：
32                 from scrapy.utils import request
33                 from scrapy.http import Request
34                  
35                 req = Request(url=‘http://www.baidu.com?name=8&id=1‘,callback=lambda x:print(x),cookies={‘k1‘:‘vvvvv‘})
36                 result = request.request_fingerprint(req,include_headers=[‘cookies‘,])
37                  
38                 print(result)
39                  
40                 req = Request(url=‘http://www.baidu.com?id=1&name=8‘,callback=lambda x:print(x),cookies={‘k1‘:666})
41                  
42                 result = request.request_fingerprint(req,include_headers=[‘cookies‘,])
43                  
44                 print(result)
45          
46 """
47 # Ensure all spiders share same duplicates filter through redis.
48 # DUPEFILTER_CLASS = "scrapy_redis.dupefilter.RFPDupeFilter"

 1 """
 2 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
 3      
 4     a. 调度器
 5         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）
 6         SCHEDULER_QUEUE_KEY = ‘%(spider)s:requests‘                         # 调度器中请求存放在redis中的key
 7         SCHEDULER_SERIALIZER = "scrapy_redis.picklecompat"                  # 对保存到redis中的数据进行序列化，默认使用pickle
 8         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
 9         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
10         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）。
11         SCHEDULER_DUPEFILTER_KEY = ‘%(spider)s:dupefilter‘                  # 去重规则，在redis中保存时对应的key
12         SCHEDULER_DUPEFILTER_CLASS = ‘scrapy_redis.dupefilter.RFPDupeFilter‘# 去重规则对应处理的类
13  
14  
15 """
16 # Enables scheduling storing requests queue in redis.
17 SCHEDULER = "scrapy_redis.scheduler.Scheduler"
18  
19 # Default requests serializer is pickle, but it can be changed to any module
20 # with loads and dumps functions. Note that pickle is not compatible between
21 # python versions.
22 # Caveat: In python 3.x, the serializer must return strings keys and support
23 # bytes as values. Because of this reason the json or msgpack module will not
24 # work by default. In python 2.x there is no such issue and you can use
25 # ‘json‘ or ‘msgpack‘ as serializers.
26 # SCHEDULER_SERIALIZER = "scrapy_redis.picklecompat"
27  
28 # Don‘t cleanup redis queues, allows to pause/resume crawls.
29 # SCHEDULER_PERSIST = True
30  
31 # Schedule requests using a priority queue. (default)
32 # SCHEDULER_QUEUE_CLASS = ‘scrapy_redis.queue.PriorityQueue‘
33  
34 # Alternative queues.
35 # SCHEDULER_QUEUE_CLASS = ‘scrapy_redis.queue.FifoQueue‘
36 # SCHEDULER_QUEUE_CLASS = ‘scrapy_redis.queue.LifoQueue‘
37  
38 # Max idle time to prevent the spider from being closed when distributed crawling.
39 # This only works if queue class is SpiderQueue or SpiderStack,
40 # and may also block the same time when your spider start at the first time (because the queue is empty).
41 # SCHEDULER_IDLE_BEFORE_CLOSE = 10　　

1 2. 定义持久化，爬虫yield Item对象时执行RedisPipeline
2      
3     a. 将item持久化到redis时，指定key和序列化函数
4      
5         REDIS_ITEMS_KEY = ‘%(spider)s:items‘
6         REDIS_ITEMS_SERIALIZER = ‘json.dumps‘
7      
8     b. 使用列表保存item数据

 1 """
 2 起始URL相关
 3  
 4     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
 5         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
 6     b. 编写爬虫时，起始URL从redis的Key中获取
 7         REDIS_START_URLS_KEY = ‘%(name)s:start_urls‘
 8          
 9 """
10 # If True, it uses redis‘ ``spop`` operation. This could be useful if you
11 # want to avoid duplicates in your start urls list. In this cases, urls must
12 # be added via ``sadd`` command or you will get a type error from redis.
13 # REDIS_START_URLS_AS_SET = False
14  
15 # Default start urls key for RedisSpider and RedisCrawlSpider.
16 # REDIS_START_URLS_KEY = ‘%(name)s:start_urls‘