mirror of
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53 lines
1.4 KiB
Python
53 lines
1.4 KiB
Python
class PessimisticImageCacheBackend(object):
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"""
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A very safe image cache backend. Guarantees that files will always be
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available, but at the cost of hitting the storage backend.
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"""
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def is_invalid(self, file):
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if not getattr(file, '_file', None):
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# No file on object. Have to check storage.
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return not file.storage.exists(file.name)
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return False
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def validate(self, file):
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"""
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Generates a new image by running the processors on the source file.
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"""
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if self.is_invalid(file):
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file.generate(save=True)
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def invalidate(self, file):
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file.delete(save=False)
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def clear(self, file):
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file.delete(save=False)
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class NonValidatingImageCacheBackend(object):
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"""
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A backend that is super optimistic about the existence of spec files. It
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will hit your file storage much less frequently than the pessimistic
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backend, but it is technically possible for a cache file to be missing
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after validation.
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"""
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def validate(self, file):
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"""
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NonValidatingImageCacheBackend has faith, so validate's a no-op.
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"""
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pass
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def invalidate(self, file):
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"""
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Immediately generate a new spec file upon invalidation.
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"""
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file.generate(save=True)
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def clear(self, file):
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file.delete(save=False)
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