How to get the scrapy failure URLs?

Yes, this is possible.

• The code below adds a failed_urls list to a basic spider class and appends urls to it if the response status of the url is 404 (this would need to be extended to cover other error statuses as required).
• Next I added a handle that joins the list into a single string and adds it to the spider’s stats when the spider is closed.
• Based on your comments, it’s possible to track Twisted errors, and some of the answers below give examples on how to handle that particular use case
• The code has been updated to work with Scrapy 1.8. All thanks to this should go to Juliano Mendieta, since all I did was simply to add his suggested edits and confirm that the spider worked as intended.

---

from scrapy import Spider, signals

class MySpider(Spider):
    handle_httpstatus_list = [404] 
    name = "myspider"
    allowed_domains = ["example.com"]
    start_urls = [
        'http://www.example.com/thisurlexists.html',
        'http://www.example.com/thisurldoesnotexist.html',
        'http://www.example.com/neitherdoesthisone.html'
    ]

    def __init__(self, *args, **kwargs):
            super().__init__(*args, **kwargs)
            self.failed_urls = []

    @classmethod
    def from_crawler(cls, crawler, *args, **kwargs):
        spider = super(MySpider, cls).from_crawler(crawler, *args, **kwargs)
        crawler.signals.connect(spider.handle_spider_closed, signals.spider_closed)
        return spider

    def parse(self, response):
        if response.status == 404:
            self.crawler.stats.inc_value('failed_url_count')
            self.failed_urls.append(response.url)

    def handle_spider_closed(self, reason):
        self.crawler.stats.set_value('failed_urls', ', '.join(self.failed_urls))

    def process_exception(self, response, exception, spider):
        ex_class = "%s.%s" % (exception.__class__.__module__, exception.__class__.__name__)
        self.crawler.stats.inc_value('downloader/exception_count', spider=spider)
        self.crawler.stats.inc_value('downloader/exception_type_count/%s' % ex_class, spider=spider)

---

Example output (note that the downloader/exception_count* stats will only appear if exceptions are actually thrown – I simulated them by trying to run the spider after I’d turned off my wireless adapter):

2012-12-10 11:15:26+0000 [myspider] INFO: Dumping Scrapy stats:
    {'downloader/exception_count': 15,
     'downloader/exception_type_count/twisted.internet.error.DNSLookupError': 15,
     'downloader/request_bytes': 717,
     'downloader/request_count': 3,
     'downloader/request_method_count/GET': 3,
     'downloader/response_bytes': 15209,
     'downloader/response_count': 3,
     'downloader/response_status_count/200': 1,
     'downloader/response_status_count/404': 2,
     'failed_url_count': 2,
     'failed_urls': 'http://www.example.com/thisurldoesnotexist.html, http://www.example.com/neitherdoesthisone.html'
     'finish_reason': 'finished',
     'finish_time': datetime.datetime(2012, 12, 10, 11, 15, 26, 874000),
     'log_count/DEBUG': 9,
     'log_count/ERROR': 2,
     'log_count/INFO': 4,
     'response_received_count': 3,
     'scheduler/dequeued': 3,
     'scheduler/dequeued/memory': 3,
     'scheduler/enqueued': 3,
     'scheduler/enqueued/memory': 3,
     'spider_exceptions/NameError': 2,
     'start_time': datetime.datetime(2012, 12, 10, 11, 15, 26, 560000)}