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43 lines
1.7 KiB
Python
43 lines
1.7 KiB
Python
# -*- coding: utf-8 -*-
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from __future__ import absolute_import
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from imagekit.imagecache import PessimisticImageCacheBackend, InvalidImageCacheBackendError
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def generate(model, pk, attr):
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try:
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instance = model._default_manager.get(pk=pk)
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except model.DoesNotExist:
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pass # The model was deleted since the task was scheduled. NEVER MIND!
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else:
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field_file = getattr(instance, attr)
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field_file.delete(save=False)
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field_file.generate(save=True)
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class CeleryImageCacheBackend(PessimisticImageCacheBackend):
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"""
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A pessimistic cache state backend that uses celery to generate its spec
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images. Like PessimisticCacheStateBackend, this one checks to see if the
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file exists on validation, so the storage is hit fairly frequently, but an
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image is guaranteed to exist. However, while validation guarantees the
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existence of *an* image, it does not necessarily guarantee that you will get
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the correct image, as the spec may be pending regeneration. In other words,
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while there are `generate` tasks in the queue, it is possible to get a
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stale spec image. The tradeoff is that calling `invalidate()` won't block
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to interact with file storage.
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"""
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def __init__(self):
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try:
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from celery.task import task
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except:
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raise InvalidImageCacheBackendError("Celery image cache backend requires the 'celery' library")
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if not getattr(CeleryImageCacheBackend, '_task', None):
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CeleryImageCacheBackend._task = task(generate)
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def invalidate(self, file):
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self._task.delay(file.instance.__class__, file.instance.pk, file.attname)
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def clear(self, file):
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file.delete(save=False)
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