"""
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.
"""
from logging import getLogger, Logger
from typing import Optional, Union
from twisted.internet import defer
from twisted.internet.error import (
ConnectError,
ConnectionDone,
ConnectionLost,
ConnectionRefusedError,
DNSLookupError,
TCPTimedOutError,
TimeoutError,
)
from twisted.web.client import ResponseFailed
from scrapy.core.downloader.handlers.http11 import TunnelError
from scrapy.exceptions import NotConfigured
from scrapy.http.request import Request
from scrapy.spiders import Spider
from scrapy.utils.python import global_object_name
from scrapy.utils.response import response_status_message
retry_logger = getLogger(__name__)
[docs]def get_retry_request(
request: Request,
*,
spider: Spider,
reason: Union[str, Exception] = 'unspecified',
max_retry_times: Optional[int] = None,
priority_adjust: Optional[int] = None,
logger: Logger = retry_logger,
stats_base_key: str = 'retry',
):
"""
Returns a new :class:`~scrapy.Request` object to retry the specified
request, or ``None`` if retries of the specified request have been
exhausted.
For example, in a :class:`~scrapy.Spider` callback, you could use it as
follows::
def parse(self, response):
if not response.text:
new_request_or_none = get_retry_request(
response.request,
spider=self,
reason='empty',
)
return new_request_or_none
*spider* is the :class:`~scrapy.Spider` instance which is asking for the
retry request. It is used to access the :ref:`settings <topics-settings>`
and :ref:`stats <topics-stats>`, and to provide extra logging context (see
:func:`logging.debug`).
*reason* is a string or an :class:`Exception` object that indicates the
reason why the request needs to be retried. It is used to name retry stats.
*max_retry_times* is a number that determines the maximum number of times
that *request* can be retried. If not specified or ``None``, the number is
read from the :reqmeta:`max_retry_times` meta key of the request. If the
:reqmeta:`max_retry_times` meta key is not defined or ``None``, the number
is read from the :setting:`RETRY_TIMES` setting.
*priority_adjust* is a number that determines how the priority of the new
request changes in relation to *request*. If not specified, the number is
read from the :setting:`RETRY_PRIORITY_ADJUST` setting.
*logger* is the logging.Logger object to be used when logging messages
*stats_base_key* is a string to be used as the base key for the
retry-related job stats
"""
settings = spider.crawler.settings
stats = spider.crawler.stats
retry_times = request.meta.get('retry_times', 0) + 1
if max_retry_times is None:
max_retry_times = request.meta.get('max_retry_times')
if max_retry_times is None:
max_retry_times = settings.getint('RETRY_TIMES')
if retry_times <= max_retry_times:
logger.debug(
"Retrying %(request)s (failed %(retry_times)d times): %(reason)s",
{'request': request, 'retry_times': retry_times, 'reason': reason},
extra={'spider': spider}
)
new_request = request.copy()
new_request.meta['retry_times'] = retry_times
new_request.dont_filter = True
if priority_adjust is None:
priority_adjust = settings.getint('RETRY_PRIORITY_ADJUST')
new_request.priority = request.priority + priority_adjust
if callable(reason):
reason = reason()
if isinstance(reason, Exception):
reason = global_object_name(reason.__class__)
stats.inc_value(f'{stats_base_key}/count')
stats.inc_value(f'{stats_base_key}/reason_count/{reason}')
return new_request
else:
stats.inc_value(f'{stats_base_key}/max_reached')
logger.error(
"Gave up retrying %(request)s (failed %(retry_times)d times): "
"%(reason)s",
{'request': request, 'retry_times': retry_times, 'reason': reason},
extra={'spider': spider},
)
return None
[docs]class RetryMiddleware:
# IOError is raised by the HttpCompression middleware when trying to
# decompress an empty response
EXCEPTIONS_TO_RETRY = (defer.TimeoutError, TimeoutError, DNSLookupError,
ConnectionRefusedError, ConnectionDone, ConnectError,
ConnectionLost, TCPTimedOutError, ResponseFailed,
IOError, TunnelError)
def __init__(self, settings):
if not settings.getbool('RETRY_ENABLED'):
raise NotConfigured
self.max_retry_times = settings.getint('RETRY_TIMES')
self.retry_http_codes = set(int(x) for x in settings.getlist('RETRY_HTTP_CODES'))
self.priority_adjust = settings.getint('RETRY_PRIORITY_ADJUST')
@classmethod
def from_crawler(cls, crawler):
return cls(crawler.settings)
def process_response(self, request, response, spider):
if request.meta.get('dont_retry', False):
return response
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)
and not request.meta.get('dont_retry', False)
):
return self._retry(request, exception, spider)
def _retry(self, request, reason, spider):
max_retry_times = request.meta.get('max_retry_times', self.max_retry_times)
priority_adjust = request.meta.get('priority_adjust', self.priority_adjust)
return get_retry_request(
request,
reason=reason,
spider=spider,
max_retry_times=max_retry_times,
priority_adjust=priority_adjust,
)