AmbiguousTimeError Celery|Django - django

Question

So i have a django site that is giving me this AmbiguousTimeError. I have a job activates when a product is saved that is given a brief timeout before updating my search index. Looks like an update was made in the Daylight Savings Time hour, and pytz cannot figure out what to do with it.
How can i prevent this from happening the next time the hour shifts for DST?
[2012-11-06 14:22:52,115: ERROR/MainProcess] Unrecoverable error: AmbiguousTimeError(datetime.datetime(2012, 11, 4, 1, 11, 4, 335637),)
Traceback (most recent call last):
File "/usr/local/lib/python2.6/dist-packages/celery/worker/__init__.py", line 353, in start
component.start()
File "/usr/local/lib/python2.6/dist-packages/celery/worker/consumer.py", line 369, in start
self.consume_messages()
File "/usr/local/lib/python2.6/dist-packages/celery/worker/consumer.py", line 842, in consume_messages
self.connection.drain_events(timeout=10.0)
File "/usr/local/lib/python2.6/dist-packages/kombu/connection.py", line 191, in drain_events
return self.transport.drain_events(self.connection, **kwargs)
File "/usr/local/lib/python2.6/dist-packages/kombu/transport/virtual/__init__.py", line 760, in drain_events
self._callbacks[queue](message)
File "/usr/local/lib/python2.6/dist-packages/kombu/transport/virtual/__init__.py", line 465, in _callback
return callback(message)
File "/usr/local/lib/python2.6/dist-packages/kombu/messaging.py", line 485, in _receive_callback
self.receive(decoded, message)
File "/usr/local/lib/python2.6/dist-packages/kombu/messaging.py", line 457, in receive
[callback(body, message) for callback in callbacks]
File "/usr/local/lib/python2.6/dist-packages/celery/worker/consumer.py", line 560, in receive_message
self.strategies[name](message, body, message.ack_log_error)
File "/usr/local/lib/python2.6/dist-packages/celery/worker/strategy.py", line 25, in task_message_handler
delivery_info=message.delivery_info))
File "/usr/local/lib/python2.6/dist-packages/celery/worker/job.py", line 120, in __init__
self.eta = tz_to_local(maybe_iso8601(eta), self.tzlocal, tz)
File "/usr/local/lib/python2.6/dist-packages/celery/utils/timeutils.py", line 52, in to_local
dt = make_aware(dt, orig or self.utc)
File "/usr/local/lib/python2.6/dist-packages/celery/utils/timeutils.py", line 211, in make_aware
return localize(dt, is_dst=None)
File "/usr/local/lib/python2.6/dist-packages/pytz/tzinfo.py", line 349, in localize
raise AmbiguousTimeError(dt)
AmbiguousTimeError: 2012-11-04 01:11:04.335637
EDIT: I fixed it temporarily with this code in celery:
celery/worker/job.py # line 120
try:
self.eta = tz_to_local(maybe_iso8601(eta), self.tzlocal, tz)
except:
self.eta = None
I don't want to have changes in a pip installed app, so i need to fix what i can in my code:
This runs when i save my app:
self.task_cls.apply_async(
args=[action, get_identifier(instance)],
countdown=15
)
I'm assuming that i need to somehow detect if i'm in the ambiguous time and adjust countdown.

Answer 1

I think i'm going to have to clear the tasks to fix this, but how can i prevent this from happening the next time the hour shifts for DST?
It's not clear what you're doing (you haven't shown any code), but basically you need to take account for the way the world works. You can't avoid having ambiguous times when you convert from local time to UTC (or to a different zone's local time) when the time goes back an hour.
Likewise you ought to be aware that there are "gap" or "impossible" times, where a reasonable-sounding local time simply doesn't occur.
I don't know what options Python gives you, but ideally an API should let you resolve ambiguous times however you want - whether that's throwing an error, giving you the earlier occurrence, the later occurrence, or something else.

Answer 2

Apparently, Celery solved this issue:
https://github.com/celery/celery/issues/1061