old_contents: # Scrapy settings for example project
  #
  # For simplicity, this file contains only the most important settings by
  # default. All the other settings are documented here:
  #
  #     http://doc.scrapy.org/topics/settings.html
  #
  SPIDER_MODULES = ['example.spiders']
  NEWSPIDER_MODULE = 'example.spiders'
  
  SCHEDULER = "scrapy_redis.scheduler.Scheduler"
  SCHEDULER_PERSIST = True
  #SCHEDULER_QUEUE_CLASS = "scrapy_redis.queue.SpiderPriorityQueue"
  #SCHEDULER_QUEUE_CLASS = "scrapy_redis.queue.SpiderQueue"
  #SCHEDULER_QUEUE_CLASS = "scrapy_redis.queue.SpiderStack"
  
  ITEM_PIPELINES = [
      'example.pipelines.ExamplePipeline',
      'scrapy_redis.pipelines.RedisPipeline',
  ]
  
new_contents: # Scrapy settings for example project
  #
  # For simplicity, this file contains only the most important settings by
  # default. All the other settings are documented here:
  #
  #     http://doc.scrapy.org/topics/settings.html
  #
  
  # -*-coding:utf-8 -*-
  
  #整体分析：在配置文件中的两部分(1)scrapy_redis.scheduler.Scheduler和
  #（2）scrapy_redis.pipelines.RedisPipeline实现分布式功能。
  
  #分布式爬取是通过（1）实现，可以实例多个spider共享redis队列中的request
  #分布式item处理是通过（2）实现。
  
  SPIDER_MODULES = ['example.spiders']
  NEWSPIDER_MODULE = 'example.spiders'
  
  #调度器
  #这里是使能调度器，将request存储到redis queue中
  
  #默认是使用scrapy.core.scheduler.Scheduler，现在使用scrapy_redis中实现的调度器。
  SCHEDULER = "scrapy_redis.scheduler.Scheduler"
  #不清空redis queue，允许爬取过程中暂停并恢复
  SCHEDULER_PERSIST = True
  #SCHEDULER_QUEUE_CLASS = "scrapy_redis.queue.SpiderPriorityQueue"
  #SCHEDULER_QUEUE_CLASS = "scrapy_redis.queue.SpiderQueue"
  #SCHEDULER_QUEUE_CLASS = "scrapy_redis.queue.SpiderStack"
  
  #在spider中得到的item会最终传到itempipline中处理，而这里设置的就是启动的pipline
  #其中第一个是自己实现的pipeline,第二个是scrapy_redis实现的pipeline
  
  #而后者对item的处理是：“将serialized item数据push进一个redis list/queue中”
  ITEM_PIPELINES = [
      'example.pipelines.ExamplePipeline',
      'scrapy_redis.pipelines.RedisPipeline',
  ]
  
subject: Add and translate comment