89 lines
3.6 KiB
Python
89 lines
3.6 KiB
Python
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from django.conf import settings
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from django.core.cache import cache
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from django.utils.httpwrappers import HttpResponseNotModified
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from django.utils.text import compress_string
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import datetime, md5
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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. Pages
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with GET or POST parameters are not cached.
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If the cache is shared across multiple sites using the same Django
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installation, set the CACHE_MIDDLEWARE_KEY_PREFIX to the name of the site,
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or some other string that is unique to this Django instance, to prevent key
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collisions.
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This middleware will also make the following optimizations:
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* If the CACHE_MIDDLEWARE_GZIP setting is True, the content will be
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gzipped.
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* ETags will be added, using a simple MD5 hash of the page's content.
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"""
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def process_request(self, request):
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"""
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Checks whether the page is already cached. If it is, returns the cached
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version. Also handles ETag stuff.
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"""
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if request.GET or request.POST:
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request._cache_middleware_set_cache = False
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return None # Don't bother checking the cache.
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accept_encoding = ''
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if settings.CACHE_MIDDLEWARE_GZIP:
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try:
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accept_encoding = request.META['HTTP_ACCEPT_ENCODING']
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except KeyError:
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pass
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accepts_gzip = 'gzip' in accept_encoding
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request._cache_middleware_accepts_gzip = accepts_gzip
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# This uses the same cache_key as views.decorators.cache.cache_page,
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# so the cache can be shared.
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cache_key = 'views.decorators.cache.cache_page.%s.%s.%s' % \
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(settings.CACHE_MIDDLEWARE_KEY_PREFIX, request.path, accepts_gzip)
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request._cache_middleware_key = cache_key
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response = cache.get(cache_key, None)
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if response is None:
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request._cache_middleware_set_cache = True
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return None
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else:
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request._cache_middleware_set_cache = False
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# Logic is from http://simon.incutio.com/archive/2003/04/23/conditionalGet
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try:
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if_none_match = request.META['HTTP_IF_NONE_MATCH']
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except KeyError:
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if_none_match = None
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try:
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if_modified_since = request.META['HTTP_IF_MODIFIED_SINCE']
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except KeyError:
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if_modified_since = None
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if if_none_match is None and if_modified_since is None:
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pass
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elif if_none_match is not None and response['ETag'] != if_none_match:
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pass
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elif if_modified_since is not None and response['Last-Modified'] != if_modified_since:
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pass
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else:
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return HttpResponseNotModified()
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return response
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def process_response(self, request, response):
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"""
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Sets the cache, if needed.
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"""
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if request._cache_middleware_set_cache:
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content = response.get_content_as_string('utf-8')
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if request._cache_middleware_accepts_gzip:
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content = compress_string(content)
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response.content = content
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response['Content-Encoding'] = 'gzip'
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response['ETag'] = md5.new(content).hexdigest()
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response['Content-Length'] = '%d' % len(content)
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response['Last-Modified'] = datetime.datetime.utcnow().strftime('%a, %d %b %Y %H:%M:%S GMT')
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cache.set(request._cache_middleware_key, response, settings.CACHE_MIDDLEWARE_SECONDS)
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return response
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