如何解决Scrapy中间件多次process_spider_exception调用
我在蜘蛛上附加了“自定义蜘蛛中间件”,并希望对蜘蛛回叫或以前的中间件中引发的异常执行特定的操作。为此,我将中间件添加到了蜘蛛中间件列表的开头,并对其进行了测试,以在蜘蛛回调中引发简单的“零除”异常。 附加的中间件的最终列表如下所示:
['rmq.middlewares.rmq_signals_spider_middleware.RMQSignalsSpiderMiddleware','scrapy.spidermiddlewares.httperror.HttpErrorMiddleware','rmq.middlewares.task_toss_spider_middleware.TaskTossSpiderMiddleware','rmq.middlewares.delivery_tag_spider_middleware.DeliveryTagSpiderMiddleware','scrapy.spidermiddlewares.offsite.OffsiteMiddleware','scrapy.spidermiddlewares.referer.RefererMiddleware','scrapy.spidermiddlewares.urllength.UrlLengthMiddleware','scrapy.spidermiddlewares.depth.DepthMiddleware']
与我在测试中概述的process_spider_exception方法的多次执行有关的问题。执行次数取决于中间件在列表中的位置。 我已将process_spider_exception添加到所有中间件,并通过输出日志收到下一个结果:
2020-08-15 10:54:10 [scrapy.spidermiddlewares.depth] WARNING: DepthMiddleware - process_spider_exception
2020-08-15 10:54:10 [scrapy.spidermiddlewares.urllength] WARNING: UrlLengthMiddleware process_spider_exception
2020-08-15 10:54:10 [root] WARNING: RefererMiddleware - process_spider_exception
2020-08-15 10:54:10 [scrapy.spidermiddlewares.offsite] WARNING: OffsiteMiddleware - process_spider_exception
2020-08-15 10:54:10 [root] WARNING: DeliveryTagSpiderMiddleware - process_spider_exception
2020-08-15 10:54:10 [root] WARNING: TaskTossSpiderMiddleware process_spider_exception
2020-08-15 10:54:10 [root] WARNING: HttpErrorMiddleware - process_spider_exception - return None
2020-08-15 10:54:10 [rmq.middlewares.rmq_signals_spider_middleware] WARNING: rmq_signals process_spider_exception
2020-08-15 10:54:10 [rmq.middlewares.rmq_signals_spider_middleware] INFO: division by zero
2020-08-15 10:54:13 [scrapy.spidermiddlewares.urllength] WARNING: UrlLengthMiddleware process_spider_exception
2020-08-15 10:54:13 [root] WARNING: RefererMiddleware - process_spider_exception
2020-08-15 10:54:13 [scrapy.spidermiddlewares.offsite] WARNING: OffsiteMiddleware - process_spider_exception
2020-08-15 10:54:13 [root] WARNING: DeliveryTagSpiderMiddleware - process_spider_exception
2020-08-15 10:54:13 [root] WARNING: TaskTossSpiderMiddleware process_spider_exception
2020-08-15 10:54:13 [root] WARNING: HttpErrorMiddleware - process_spider_exception - return None
2020-08-15 10:54:13 [rmq.middlewares.rmq_signals_spider_middleware] WARNING: rmq_signals process_spider_exception
2020-08-15 10:54:13 [rmq.middlewares.rmq_signals_spider_middleware] INFO: division by zero
2020-08-15 10:54:16 [root] WARNING: RefererMiddleware - process_spider_exception
2020-08-15 10:54:16 [scrapy.spidermiddlewares.offsite] WARNING: OffsiteMiddleware - process_spider_exception
2020-08-15 10:54:16 [root] WARNING: DeliveryTagSpiderMiddleware - process_spider_exception
2020-08-15 10:54:16 [root] WARNING: TaskTossSpiderMiddleware process_spider_exception
2020-08-15 10:54:16 [root] WARNING: HttpErrorMiddleware - process_spider_exception - return None
2020-08-15 10:54:16 [rmq.middlewares.rmq_signals_spider_middleware] WARNING: rmq_signals process_spider_exception
2020-08-15 10:54:16 [rmq.middlewares.rmq_signals_spider_middleware] INFO: division by zero
2020-08-15 10:54:19 [scrapy.spidermiddlewares.offsite] WARNING: OffsiteMiddleware - process_spider_exception
2020-08-15 10:54:19 [root] WARNING: DeliveryTagSpiderMiddleware - process_spider_exception
2020-08-15 10:54:19 [root] WARNING: TaskTossSpiderMiddleware process_spider_exception
2020-08-15 10:54:19 [root] WARNING: HttpErrorMiddleware - process_spider_exception - return None
2020-08-15 10:54:19 [rmq.middlewares.rmq_signals_spider_middleware] WARNING: rmq_signals process_spider_exception
2020-08-15 10:54:19 [rmq.middlewares.rmq_signals_spider_middleware] INFO: division by zero
2020-08-15 10:54:22 [root] WARNING: DeliveryTagSpiderMiddleware - process_spider_exception
2020-08-15 10:54:22 [root] WARNING: TaskTossSpiderMiddleware process_spider_exception
2020-08-15 10:54:22 [root] WARNING: HttpErrorMiddleware - process_spider_exception - return None
2020-08-15 10:54:22 [rmq.middlewares.rmq_signals_spider_middleware] WARNING: rmq_signals process_spider_exception
2020-08-15 10:54:22 [rmq.middlewares.rmq_signals_spider_middleware] INFO: division by zero
2020-08-15 10:54:25 [root] WARNING: TaskTossSpiderMiddleware process_spider_exception
2020-08-15 10:54:25 [root] WARNING: HttpErrorMiddleware - process_spider_exception - return None
2020-08-15 10:54:25 [rmq.middlewares.rmq_signals_spider_middleware] WARNING: rmq_signals process_spider_exception
2020-08-15 10:54:25 [rmq.middlewares.rmq_signals_spider_middleware] INFO: division by zero
2020-08-15 10:54:28 [root] WARNING: HttpErrorMiddleware - process_spider_exception - return None
2020-08-15 10:54:28 [rmq.middlewares.rmq_signals_spider_middleware] WARNING: rmq_signals process_spider_exception
2020-08-15 10:54:28 [rmq.middlewares.rmq_signals_spider_middleware] INFO: division by zero
2020-08-15 10:54:31 [scrapy.core.scraper] ERROR: Spider error processing <GET https://HIDDEN_LINK>
(referer: None)
Traceback (most recent call last):
File "/var/www/scrapy-boilerplate/.venv/lib/python3.8/site-packages/scrapy/utils/defer.py",line 120,in iter_errback
yield next(it)
File "/var/www/scrapy-boilerplate/.venv/lib/python3.8/site-packages/scrapy/utils/python.py",line 346,in __next__
return next(self.data)
process_spider_exception方法按如下顺序执行: 最后一个Mw->(最后1个)mw-> ...->我的mw-> ...-> 1个Mw->(最后-1个)mw-> ...->我的Mw-> ... -> 1兆瓦->(最后-2)兆瓦-> ...
并且只有在这种“堆栈”之后,才记录/记录异常。 在documentation之后,据我所知,预期的行为是所有process_spider_exception方法的唯一一次执行。但是如果n是使用的中间件的总数,我得到(n-1)。
我的问题是关于这种行为本身的:有人可以解释它是如何工作或应该如何工作。是预期的行为,还是这是github问题的潜在主题?
此外,我敢肯定,我可以使用某种“一次调用”修饰器或类似方法来解决我的问题。
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