how to filter duplicate requests based on url in scrapy

Question

I am writing a crawler for a website using scrapy with CrawlSpider.

Scrapy provides an in-built duplicate-request filter which filters duplicate requests based on ur

Answer 1

https://github.com/scrapinghub/scrapylib/blob/master/scrapylib/deltafetch.py

This file might help you. This file creates a database of unique delta fetch key from the url ,a user pass in a scrapy.Reqeust(meta={'deltafetch_key':uniqe_url_key}). This this let you avoid duplicate requests you already have visited in the past.

A sample mongodb implementation using deltafetch.py

        if isinstance(r, Request):
            key = self._get_key(r)
            key = key+spider.name

            if self.db['your_collection_to_store_deltafetch_key'].find_one({"_id":key}):
                spider.log("Ignoring already visited: %s" % r, level=log.INFO)
                continue
        elif isinstance(r, BaseItem):

            key = self._get_key(response.request)
            key = key+spider.name
            try:
                self.db['your_collection_to_store_deltafetch_key'].insert({"_id":key,"time":datetime.now()})
            except:
                spider.log("Ignoring already visited: %s" % key, level=log.ERROR)
        yield r

eg. id = 345 scrapy.Request(url,meta={deltafetch_key:345},callback=parse)