据我了解,Scrapy是单线程的,但在网络端是异步的。我正在研究需要从项目管道中对外部资源进行 API 调用的事情。有没有办法在不阻塞管道和减慢 Scrapy 爬行速度的情况下发出 HTTP 请求?
谢谢
您可以通过
crawler.engine.crawl(request, spider)
直接向crawler.engine
调度请求来实现。要做到这一点,你需要在管道中公开爬虫:
class MyPipeline(object):
def __init__(self, crawler):
self.crawler = crawler
@classmethod
def from_crawler(cls, crawler):
return cls(crawler)
def process_item(self, item, spider):
if item['some_extra_field']: # check if we already did below
return item
url = 'some_url'
req = scrapy.Request(url, self.parse_item, meta={'item':item})
self.crawler.engine.crawl(req, spider)
raise DropItem() # we will get this item next time
def parse_item(self, response):
item = response.meta['item']
item['some_extra_field'] = '...'
return item