把起始URL放到redis中去
    from scrapy_redis.spiders import RedisSpider
    # 继承RedisSpider
    class ChoutiSpider(RedisSpider):
        name = ‘chouti‘
        allowed_domains = [‘chouti.com‘]
    配置文件：
        REDIS_START_URLS_KEY = ‘%(name)s:start_urls‘
        REDIS_START_URLS_AS_SET = False
        下面是源码
        # use_set = self.settings.getbool(‘REDIS_START_URLS_AS_SET‘, defaults.START_URLS_AS_SET)
        # fetch_one = self.server.spop if use_set else self.server.lpop