""" 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_alias = settings.CACHE_MIDDLEWARE_ALIAS self.cache = get_cache(self.cache_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) if hasattr(response, 'render') and callable(response.render): response.add_post_render_callback( lambda r: self.cache.set(cache_key, r, timeout) ) else: 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_alias = settings.CACHE_MIDDLEWARE_ALIAS self.cache = get_cache(self.cache_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['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: self.cache_alias = kwargs['cache_alias'] if self.cache_alias is None: self.cache_alias = DEFAULT_CACHE_ALIAS if cache_timeout is not None: cache_kwargs['TIMEOUT'] = cache_timeout except KeyError: self.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(self.cache_alias, **cache_kwargs) self.cache_timeout = self.cache.default_timeout