scrapy-redis的使用與解析

時間 2019-11-21

原文原文鏈接

scrapy-redis是一個基於redis的scrapy組件，經過它能夠快速實現簡單分佈式爬蟲程序，該組件本質上提供了三大功能：html

scheduler - 調度器
dupefilter - URL去重規則（被調度器使用）
pipeline - 數據持久化

scrapy-redis組件

1. URL去重python

定義去重規則（被調度器調用並應用）

    a. 內部會使用如下配置進行鏈接Redis

        # REDIS_HOST = 'localhost'                            # 主機名
        # REDIS_PORT = 6379                                   # 端口
        # REDIS_URL = 'redis://user:pass@hostname:9001'       # 鏈接URL（優先於以上配置）
        # REDIS_PARAMS  = {}                                  # Redis鏈接參數             默認：REDIS_PARAMS = {'socket_timeout': 30,'socket_connect_timeout': 30,'retry_on_timeout': True,'encoding': REDIS_ENCODING,}）
        # REDIS_PARAMS['redis_cls'] = 'myproject.RedisClient' # 指定鏈接Redis的Python模塊  默認：redis.StrictRedis
        # REDIS_ENCODING = "utf-8"                            # redis編碼類型             默認：'utf-8'
    
    b. 去重規則經過redis的集合完成，集合的Key爲：
    
        key = defaults.DUPEFILTER_KEY % {'timestamp': int(time.time())}
        默認配置：
            DUPEFILTER_KEY = 'dupefilter:%(timestamp)s'
             
    c. 去重規則中將url轉換成惟一標示，而後在redis中檢查是否已經在集合中存在
    
        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參數位置不一樣時，計算結果一致；
            - 默認請求頭不在計算範圍，include_headers能夠設置指定請求頭
            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. 調度器redis

"""
調度器，調度器使用PriorityQueue（有序集合）、FifoQueue（列表）、LifoQueue（列表）進行保存請求，而且使用RFPDupeFilter對URL去重
    
    a. 調度器
        SCHEDULER_QUEUE_CLASS = 'scrapy_redis.queue.PriorityQueue'          # 默認使用優先級隊列（默認），其餘：PriorityQueue（有序集合），FifoQueue（列表）、LifoQueue（列表）
        SCHEDULER_QUEUE_KEY = '%(spider)s:requests'                         # 調度器中請求存放在redis中的key
        SCHEDULER_SERIALIZER = "scrapy_redis.picklecompat"                  # 對保存到redis中的數據進行序列化，默認使用pickle
        SCHEDULER_PERSIST = True                                            # 是否在關閉時候保留原來的調度器和去重記錄，True=保留，False=清空
        SCHEDULER_FLUSH_ON_START = True                                     # 是否在開始以前清空 調度器和去重記錄，True=清空，False=不清空
        SCHEDULER_IDLE_BEFORE_CLOSE = 10                                    # 去調度器中獲取數據時，若是爲空，最多等待時間（最後沒數據，未獲取到）。
        SCHEDULER_DUPEFILTER_KEY = '%(spider)s:dupefilter'                  # 去重規則，在redis中保存時對應的key
        SCHEDULER_DUPEFILTER_CLASS = 'scrapy_redis.dupefilter.RFPDupeFilter'# 去重規則對應處理的類


"""
# 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. 數據持久化json

2. 定義持久化，爬蟲yield Item對象時執行RedisPipeline
    
    a. 將item持久化到redis時，指定key和序列化函數
    
        REDIS_ITEMS_KEY = '%(spider)s:items'
        REDIS_ITEMS_SERIALIZER = 'json.dumps'
    
    b. 使用列表保存item數據

4. 起始URL相關cookie

"""
起始URL相關

    a. 獲取起始URL時，去集合中獲取仍是去列表中獲取？True，集合；False，列表
        REDIS_START_URLS_AS_SET = False    # 獲取起始URL時，若是爲True，則使用self.server.spop；若是爲False，則使用self.server.lpop
    b. 編寫爬蟲時，起始URL從redis的Key中獲取
        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

# 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'          # 默認使用優先級隊列（默認），其餘：PriorityQueue（有序集合），FifoQueue（列表）、LifoQueue（列表）
# SCHEDULER_QUEUE_KEY = '%(spider)s:requests'                         # 調度器中請求存放在redis中的key
# SCHEDULER_SERIALIZER = "scrapy_redis.picklecompat"                  # 對保存到redis中的數據進行序列化，默認使用pickle
# SCHEDULER_PERSIST = True                                            # 是否在關閉時候保留原來的調度器和去重記錄，True=保留，False=清空
# SCHEDULER_FLUSH_ON_START = False                                    # 是否在開始以前清空 調度器和去重記錄，True=清空，False=不清空
# SCHEDULER_IDLE_BEFORE_CLOSE = 10                                    # 去調度器中獲取數據時，若是爲空，最多等待時間（最後沒數據，未獲取到）。
# SCHEDULER_DUPEFILTER_KEY = '%(spider)s:dupefilter'                  # 去重規則，在redis中保存時對應的key
# SCHEDULER_DUPEFILTER_CLASS = 'scrapy_redis.dupefilter.RFPDupeFilter'# 去重規則對應處理的類
#
#
#
# REDIS_HOST = '10.211.55.13'                           # 主機名
# REDIS_PORT = 6379                                     # 端口
# # REDIS_URL = 'redis://user:pass@hostname:9001'       # 鏈接URL（優先於以上配置）
# # REDIS_PARAMS  = {}                                  # Redis鏈接參數             默認：REDIS_PARAMS = {'socket_timeout': 30,'socket_connect_timeout': 30,'retry_on_timeout': True,'encoding': REDIS_ENCODING,}）
# # REDIS_PARAMS['redis_cls'] = 'myproject.RedisClient' # 指定鏈接Redis的Python模塊  默認：redis.StrictRedis
# REDIS_ENCODING = "utf-8"                              # redis編碼類型             默認：'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