forked from CGM_Public/pretix_original
64 lines
2.3 KiB
Python
64 lines
2.3 KiB
Python
import logging
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import uuid
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from functools import wraps
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from django.core.cache import cache
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logger = logging.getLogger(__name__)
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SKIPPED = object()
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def minimum_interval(minutes_after_success, minutes_after_error=0, minutes_running_timeout=30):
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"""
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This is intended to be used as a decorator on receivers of the ``periodic_task`` signal.
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It stores the result in the task in the cache (usually redis) to ensure the receiver function
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isn't executed less than ``minutes_after_success`` after the last successful run and no less
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than ``minutes_after_error`` after the last failed run. There's also a simple locking mechanism
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implemented making sure the function is not called a second time while it is running, unless
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``minutes_running_timeout`` have passed. This locking mechanism is naive and not safe of
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race-conditions, it should not be relied upon.
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"""
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def deco(f):
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@wraps(f)
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def wrapper(*args, **kwargs):
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key_running = f'pretix_periodic_{f.__module__}.{f.__name__}_running'
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key_result = f'pretix_periodic_{f.__module__}.{f.__name__}_result'
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running_val = cache.get(key_running)
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if running_val:
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# Currently running
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return SKIPPED
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result_val = cache.get(key_result)
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if result_val:
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# Has run recently
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return SKIPPED
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uniqid = str(uuid.uuid4())
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cache.set(key_running, uniqid, timeout=minutes_running_timeout * 60)
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try:
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retval = f(*args, **kwargs)
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except Exception as e:
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try:
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cache.set(key_result, 'error', timeout=minutes_after_error * 60)
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except:
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logger.exception('Could not store result')
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raise e
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else:
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try:
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cache.set(key_result, 'success', timeout=minutes_after_success * 60)
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except:
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logger.exception('Could not store result')
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return retval
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finally:
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try:
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if cache.get(key_running) == uniqid:
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cache.delete(key_running)
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except:
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logger.exception('Could not release lock')
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return wrapper
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return deco
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