70 lines
3.0 KiB
Python
70 lines
3.0 KiB
Python
from django.conf import settings
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from django.core.cache import cache
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from django.utils.cache import get_cache_key, learn_cache_key, patch_response_headers
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from django.utils.httpwrappers import HttpResponseNotModified
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class CacheMiddleware:
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"""
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Cache middleware. If this is enabled, each Django-powered page will be
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cached for CACHE_MIDDLEWARE_SECONDS seconds. Cache is based on URLs.
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Only parameter-less GET or HEAD-requests with status code 200 are cached.
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This middleware expects that a HEAD request is answered with a response
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exactly like the corresponding GET request.
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When a hit occurs, a shallow copy of the original response object is
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returned from process_request.
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Pages will be cached based on the contents of the request headers
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listed in the response's "Vary" header. This means that pages shouldn't
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change their "Vary" header.
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This middleware also sets ETag, Last-Modified, Expires and Cache-Control
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headers on the response object.
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"""
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def __init__(self, cache_timeout=None, key_prefix=None):
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self.cache_timeout = cache_timeout
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if cache_timeout is None:
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self.cache_timeout = settings.CACHE_MIDDLEWARE_SECONDS
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self.key_prefix = key_prefix
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if key_prefix is None:
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self.key_prefix = settings.CACHE_MIDDLEWARE_KEY_PREFIX
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def process_request(self, request):
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"Checks whether the page is already cached and returns the cached version if available."
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if not request.META['REQUEST_METHOD'] in ('GET', 'HEAD') or request.GET:
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request._cache_update_cache = False
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return None # Don't bother checking the cache.
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cache_key = get_cache_key(request, self.key_prefix)
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if cache_key is None:
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request._cache_update_cache = True
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return None # No cache information available, need to rebuild.
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response = cache.get(cache_key, None)
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if response is None:
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request._cache_update_cache = True
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return None # No cache information available, need to rebuild.
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request._cache_update_cache = False
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return response
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def process_response(self, request, response):
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"Sets the cache, if needed."
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if not hasattr(request, '_cache_update_cache') or not request._cache_update_cache:
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# We don't need to update the cache, just return.
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return response
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if not request.META['REQUEST_METHOD'] == 'GET':
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# This is a stronger requirement than above. It is needed
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# because of interactions between this middleware and the
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# HTTPMiddleware, which throws the body of a HEAD-request
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# away before this middleware gets a chance to cache it.
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return response
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if not response.status_code == 200:
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return response
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patch_response_headers(response, self.cache_timeout)
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cache_key = learn_cache_key(request, response, self.cache_timeout, self.key_prefix)
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cache.set(cache_key, response, self.cache_timeout)
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return response
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