从Scrapy管道发出非阻塞HTTP请求

Question

据我了解，Scrapy是单线程但在网络端是异步的。我正在开发一些需要从项目管道中对外部资源进行API调用的东西。有没有办法在不阻塞管道的情况下发出HTTP请求并减慢Scrapy的爬行速度？

由于

Answer 1

您可以通过crawler.engine将请求直接安排到crawler.engine.crawl(request, spider)。但要做到这一点，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