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"""
An extension to retry failed requests that are potentially caused by temporary
problems such as a connection timeout or HTTP 500 error.
You can change the behaviour of this middleware by modifing the scraping settings:
RETRY_TIMES - how many times to retry a failed page
RETRY_HTTP_CODES - which HTTP response codes to retry
Failed pages are collected on the scraping process and rescheduled at the end,
once the spider has finished crawling all regular (non failed) pages. Once
there is no more failed pages to retry this middleware sends a signal
(retry_complete), so other extensions could connect to that signal.
Default values are located in scrapy.conf.default_settings, like any other
setting
About HTTP errors to consider:
- You may want to remove 400 from RETRY_HTTP_CODES, if you stick to the HTTP
protocol. It's included by default because it's a common code used to
indicate server overload, which would be something we want to retry
"""
from twisted.internet.error import TimeoutError as ServerTimeoutError, DNSLookupError, \
ConnectionRefusedError, ConnectionDone, ConnectError, \
ConnectionLost
from twisted.internet.defer import TimeoutError as UserTimeoutError
from twisted.web.client import PartialDownloadError
from scrapy import log
from scrapy.utils.request import request_fingerprint
from scrapy.utils.response import response_status_message
from scrapy.conf import settings
class RetryMiddleware(object):
EXCEPTIONS_TO_RETRY = (ServerTimeoutError, UserTimeoutError, DNSLookupError,
ConnectionRefusedError, ConnectionDone, ConnectError,
ConnectionLost, PartialDownloadError)
def __init__(self):
self.max_retry_times = settings.getint('RETRY_TIMES')
self.retry_http_codes = map(int, settings.getlist('RETRY_HTTP_CODES'))
self.priority_adjust = settings.getint('RETRY_PRIORITY_ADJUST')
def process_response(self, request, response, spider):
if response.status in self.retry_http_codes:
reason = response_status_message(response.status)
return self._retry(request, reason, spider) or response
return response
def process_exception(self, request, exception, spider):
if isinstance(exception, self.EXCEPTIONS_TO_RETRY):
return self._retry(request, exception, spider)
def _retry(self, request, reason, spider):
retries = request.meta.get('retry_times', 0) + 1
if retries <= self.max_retry_times:
log.msg("Retrying %s (failed %d times): %s" % (request, retries, reason),
spider=spider, level=log.DEBUG)
retryreq = request.copy()
retryreq.meta['retry_times'] = retries
retryreq.dont_filter = True
retryreq.priority = request.priority + self.priority_adjust
return retryreq
else:
log.msg("Discarding %s (failed %d times): %s" % (request, retries, reason),
spider=spider, level=log.DEBUG)
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