4e22affb24
When releasing the versioned assets work, we stumbled on a problem with old pickled versions of the StaticContent objects residing in cache, which triggered a bug in the code. Not wanting to blow away all cached items, we ended up having to revert and add in some backwards-compatible helper code to ease the transition. With this, we'll now utilize the version argument that Django's caching interface allows, in conjunction with a constant value that can be modified when breaking changes are being made, to let us gracefully ignore older cached course assets.
50 lines
1.6 KiB
Python
50 lines
1.6 KiB
Python
"""
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Helper functions for caching course assets.
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"""
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from django.core.cache import caches
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from django.core.cache.backends.base import InvalidCacheBackendError
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from opaque_keys import InvalidKeyError
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from . import CONTENTSERVER_VERSION
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# See if there's a "course_assets" cache configured, and if not, fallback to the default cache.
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CONTENT_CACHE = caches['default']
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try:
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CONTENT_CACHE = caches['course_assets']
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except InvalidCacheBackendError:
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pass
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def set_cached_content(content):
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"""
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Stores the given piece of content in the cache, using its location as the key.
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"""
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CONTENT_CACHE.set(unicode(content.location).encode("utf-8"), content, version=CONTENTSERVER_VERSION)
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def get_cached_content(location):
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"""
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Retrieves the given piece of content by its location if cached.
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"""
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return CONTENT_CACHE.get(unicode(location).encode("utf-8"), version=CONTENTSERVER_VERSION)
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def del_cached_content(location):
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"""
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Delete content for the given location, as well versions of the content without a run.
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It's possible that the content could have been cached without knowing the course_key,
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and so without having the run.
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"""
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def location_str(loc):
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"""Force the location to a Unicode string."""
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return unicode(loc).encode("utf-8")
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locations = [location_str(location)]
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try:
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locations.append(location_str(location.replace(run=None)))
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except InvalidKeyError:
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# although deprecated keys allowed run=None, new keys don't if there is no version.
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pass
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CONTENT_CACHE.delete_many(locations, version=CONTENTSERVER_VERSION)
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