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"""Helper functions for working with signals"""
import logging
from twisted.internet.defer import DeferredList, Deferred
from twisted.python.failure import Failure
from pydispatch.dispatcher import Anonymous, Any, disconnect, getAllReceivers, liveReceivers
from pydispatch.robustapply import robustApply
from scrapy.exceptions import StopDownload
from scrapy.utils.defer import maybeDeferred_coro
from scrapy.utils.log import failure_to_exc_info
logger = logging.getLogger(__name__)
class _IgnoredException(Exception):
pass
def send_catch_log(signal=Any, sender=Anonymous, *arguments, **named):
"""Like pydispatcher.robust.sendRobust but it also logs errors and returns
Failures instead of exceptions.
"""
dont_log = (named.pop('dont_log', _IgnoredException), StopDownload)
spider = named.get('spider', None)
responses = []
for receiver in liveReceivers(getAllReceivers(sender, signal)):
try:
response = robustApply(receiver, signal=signal, sender=sender, *arguments, **named)
if isinstance(response, Deferred):
logger.error("Cannot return deferreds from signal handler: %(receiver)s",
{'receiver': receiver}, extra={'spider': spider})
except dont_log:
result = Failure()
except Exception:
result = Failure()
logger.error("Error caught on signal handler: %(receiver)s",
{'receiver': receiver},
exc_info=True, extra={'spider': spider})
else:
result = response
responses.append((receiver, result))
return responses
def send_catch_log_deferred(signal=Any, sender=Anonymous, *arguments, **named):
"""Like send_catch_log but supports returning deferreds on signal handlers.
Returns a deferred that gets fired once all signal handlers deferreds were
fired.
"""
def logerror(failure, recv):
if dont_log is None or not isinstance(failure.value, dont_log):
logger.error("Error caught on signal handler: %(receiver)s",
{'receiver': recv},
exc_info=failure_to_exc_info(failure),
extra={'spider': spider})
return failure
dont_log = named.pop('dont_log', None)
spider = named.get('spider', None)
dfds = []
for receiver in liveReceivers(getAllReceivers(sender, signal)):
d = maybeDeferred_coro(robustApply, receiver, signal=signal, sender=sender, *arguments, **named)
d.addErrback(logerror, receiver)
d.addBoth(lambda result: (receiver, result))
dfds.append(d)
d = DeferredList(dfds)
d.addCallback(lambda out: [x[1] for x in out])
return d
def disconnect_all(signal=Any, sender=Any):
"""Disconnect all signal handlers. Useful for cleaning up after running
tests
"""
for receiver in liveReceivers(getAllReceivers(sender, signal)):
disconnect(receiver, signal=signal, sender=sender)
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