| """ |
| Cache middleware. If enabled, each Django-powered page will be cached based on |
| URL. The canonical way to enable cache middleware is to set |
| ``UpdateCacheMiddleware`` as your first piece of middleware, and |
| ``FetchFromCacheMiddleware`` as the last:: |
| |
| MIDDLEWARE_CLASSES = [ |
| 'django.middleware.cache.UpdateCacheMiddleware', |
| ... |
| 'django.middleware.cache.FetchFromCacheMiddleware' |
| ] |
| |
| This is counter-intuitive, but correct: ``UpdateCacheMiddleware`` needs to run |
| last during the response phase, which processes middleware bottom-up; |
| ``FetchFromCacheMiddleware`` needs to run last during the request phase, which |
| processes middleware top-down. |
| |
| The single-class ``CacheMiddleware`` can be used for some simple sites. |
| However, if any other piece of middleware needs to affect the cache key, you'll |
| need to use the two-part ``UpdateCacheMiddleware`` and |
| ``FetchFromCacheMiddleware``. This'll most often happen when you're using |
| Django's ``LocaleMiddleware``. |
| |
| More details about how the caching works: |
| |
| * Only parameter-less GET or HEAD-requests with status code 200 are cached. |
| |
| * The number of seconds each page is stored for is set by the "max-age" section |
| of the response's "Cache-Control" header, falling back to the |
| CACHE_MIDDLEWARE_SECONDS setting if the section was not found. |
| |
| * If CACHE_MIDDLEWARE_ANONYMOUS_ONLY is set to True, only anonymous requests |
| (i.e., those not made by a logged-in user) will be cached. This is a simple |
| and effective way of avoiding the caching of the Django admin (and any other |
| user-specific content). |
| |
| * This middleware expects that a HEAD request is answered with the same response |
| headers exactly like the corresponding GET request. |
| |
| * When a hit occurs, a shallow copy of the original response object is returned |
| from process_request. |
| |
| * Pages will be cached based on the contents of the request headers listed in |
| the response's "Vary" header. |
| |
| * This middleware also sets ETag, Last-Modified, Expires and Cache-Control |
| headers on the response object. |
| |
| """ |
| |
| from django.conf import settings |
| from django.core.cache import get_cache, DEFAULT_CACHE_ALIAS |
| from django.utils.cache import get_cache_key, learn_cache_key, patch_response_headers, get_max_age |
| |
| class UpdateCacheMiddleware(object): |
| """ |
| Response-phase cache middleware that updates the cache if the response is |
| cacheable. |
| |
| Must be used as part of the two-part update/fetch cache middleware. |
| UpdateCacheMiddleware must be the first piece of middleware in |
| MIDDLEWARE_CLASSES so that it'll get called last during the response phase. |
| """ |
| def __init__(self): |
| self.cache_timeout = settings.CACHE_MIDDLEWARE_SECONDS |
| self.key_prefix = settings.CACHE_MIDDLEWARE_KEY_PREFIX |
| self.cache_anonymous_only = getattr(settings, 'CACHE_MIDDLEWARE_ANONYMOUS_ONLY', False) |
| self.cache = get_cache(settings.CACHE_MIDDLEWARE_ALIAS) |
| |
| def process_response(self, request, response): |
| """Sets the cache, if needed.""" |
| if not hasattr(request, '_cache_update_cache') or not request._cache_update_cache: |
| # We don't need to update the cache, just return. |
| return response |
| if not response.status_code == 200: |
| return response |
| # Try to get the timeout from the "max-age" section of the "Cache- |
| # Control" header before reverting to using the default cache_timeout |
| # length. |
| timeout = get_max_age(response) |
| if timeout == None: |
| timeout = self.cache_timeout |
| elif timeout == 0: |
| # max-age was set to 0, don't bother caching. |
| return response |
| patch_response_headers(response, timeout) |
| if timeout: |
| cache_key = learn_cache_key(request, response, timeout, self.key_prefix, cache=self.cache) |
| self.cache.set(cache_key, response, timeout) |
| return response |
| |
| class FetchFromCacheMiddleware(object): |
| """ |
| Request-phase cache middleware that fetches a page from the cache. |
| |
| Must be used as part of the two-part update/fetch cache middleware. |
| FetchFromCacheMiddleware must be the last piece of middleware in |
| MIDDLEWARE_CLASSES so that it'll get called last during the request phase. |
| """ |
| def __init__(self): |
| self.cache_timeout = settings.CACHE_MIDDLEWARE_SECONDS |
| self.key_prefix = settings.CACHE_MIDDLEWARE_KEY_PREFIX |
| self.cache_anonymous_only = getattr(settings, 'CACHE_MIDDLEWARE_ANONYMOUS_ONLY', False) |
| self.cache = get_cache(settings.CACHE_MIDDLEWARE_ALIAS) |
| |
| def process_request(self, request): |
| """ |
| Checks whether the page is already cached and returns the cached |
| version if available. |
| """ |
| if self.cache_anonymous_only: |
| assert hasattr(request, 'user'), "The Django cache middleware with CACHE_MIDDLEWARE_ANONYMOUS_ONLY=True requires authentication middleware to be installed. Edit your MIDDLEWARE_CLASSES setting to insert 'django.contrib.auth.middleware.AuthenticationMiddleware' before the CacheMiddleware." |
| |
| if not request.method in ('GET', 'HEAD') or request.GET: |
| request._cache_update_cache = False |
| return None # Don't bother checking the cache. |
| |
| if self.cache_anonymous_only and request.user.is_authenticated(): |
| request._cache_update_cache = False |
| return None # Don't cache requests from authenticated users. |
| |
| # try and get the cached GET response |
| cache_key = get_cache_key(request, self.key_prefix, 'GET', cache=self.cache) |
| if cache_key is None: |
| request._cache_update_cache = True |
| return None # No cache information available, need to rebuild. |
| response = self.cache.get(cache_key, None) |
| # if it wasn't found and we are looking for a HEAD, try looking just for that |
| if response is None and request.method == 'HEAD': |
| cache_key = get_cache_key(request, self.key_prefix, 'HEAD', cache=self.cache) |
| response = self.cache.get(cache_key, None) |
| |
| if response is None: |
| request._cache_update_cache = True |
| return None # No cache information available, need to rebuild. |
| |
| # hit, return cached response |
| request._cache_update_cache = False |
| return response |
| |
| class CacheMiddleware(UpdateCacheMiddleware, FetchFromCacheMiddleware): |
| """ |
| Cache middleware that provides basic behavior for many simple sites. |
| |
| Also used as the hook point for the cache decorator, which is generated |
| using the decorator-from-middleware utility. |
| """ |
| def __init__(self, cache_timeout=None, cache_anonymous_only=None, **kwargs): |
| # We need to differentiate between "provided, but using default value", |
| # and "not provided". If the value is provided using a default, then |
| # we fall back to system defaults. If it is not provided at all, |
| # we need to use middleware defaults. |
| |
| cache_kwargs = {} |
| try: |
| self.key_prefix = kwargs.get('key_prefix') |
| if self.key_prefix is not None: |
| cache_kwargs['KEY_PREFIX'] = self.key_prefix |
| else: |
| self.key_prefix = '' |
| except KeyError: |
| self.key_prefix = settings.CACHE_MIDDLEWARE_KEY_PREFIX |
| cache_kwargs['KEY_PREFIX'] = self.key_prefix |
| try: |
| cache_alias = kwargs.get('cache_alias') |
| if cache_alias is None: |
| cache_alias = DEFAULT_CACHE_ALIAS |
| if cache_timeout is not None: |
| cache_kwargs['TIMEOUT'] = cache_timeout |
| except KeyError: |
| cache_alias = settings.CACHE_MIDDLEWARE_ALIAS |
| if cache_timeout is None: |
| cache_kwargs['TIMEOUT'] = settings.CACHE_MIDDLEWARE_SECONDS |
| else: |
| cache_kwargs['TIMEOUT'] = cache_timeout |
| |
| if cache_anonymous_only is None: |
| self.cache_anonymous_only = getattr(settings, 'CACHE_MIDDLEWARE_ANONYMOUS_ONLY', False) |
| else: |
| self.cache_anonymous_only = cache_anonymous_only |
| |
| self.cache = get_cache(cache_alias, **cache_kwargs) |
| self.cache_timeout = self.cache.default_timeout |