Ticket #9249: cache_ignore_cookie.patch

django/conf/global_settings.py

@@ -331 +331 @@
 CACHE_BACKEND = 'locmem://'
 CACHE_MIDDLEWARE_KEY_PREFIX = ''
 CACHE_MIDDLEWARE_SECONDS = 600
+CACHE_MIDDLEWARE_IGNORE_COOKIES = ()
 
 ####################
 # COMMENTS         #

django/utils/cache.py

@@ -142 +142 @@
     ctx = md5_constructor()
     for header in headerlist:
         value = request.META.get(header, None)
-        if value is not None:
+        if header == "HTTP_COOKIE" and len(request.COOKIES) > 0:
+            cookies = request.COOKIES
+            for key in cookies.keys():
+                for re in settings.CACHE_MIDDLEWARE_IGNORE_COOKIES:
+                    if re.search(key) and cookies.has_key(key):
+                        del cookies[key]
+            if len(cookies) > 0:
+                # Builds a new header value without ignored cookies
+                ctx.update(";".join(['%s=%s' % (k,v) for k,v in cookies.items() ]))
+        elif value is not None:
             ctx.update(value)
     path = md5_constructor(iri_to_uri(request.path))
     return 'views.decorators.cache.cache_page.%s.%s.%s' % (

docs/topics/cache.txt

@@ -287 +287 @@
   sites using the same Django installation, set this to the name of the site,
   or some other string that is unique to this Django instance, to prevent key
   collisions. Use an empty string if you don't care.
+* ``CACHE_MIDDLEWARE_IGNORE_COOKIES`` -- Tuple of compiled regular expression
+  patterns of request cookies that should not be considered if "Cookie" is set
+  in ``Vary`` header. See the `Using Vary headers`_ section for more on this
+  setting.
 
 The cache middleware caches every page that doesn't have GET or POST
 parameters. Optionally, if the ``CACHE_MIDDLEWARE_ANONYMOUS_ONLY`` setting is
@@ -647 +651 @@
     def my_view(request):
         # ...
 
+If your application contains client-side Javascript code saving its
+state in cookies you may meet a problem when varying on cookie makes
+Django to cache a new copy of a page for each client cookie
+variation. You can optionally specify those client-side cookie in an
+optional ``CACHE_MIDDLEWARE_IGNORE_COOKIES`` setting, making Django to
+ignore them when building a cache key thus improving hit performance
+and memory consumption. For example, you may want to ignore Google
+Analytics tracking cookies::
+
+    import re
+    CACHE_MIDDLEWARE_IGNORE_COOKIES = (
+        re.compile('^__utm'),
+    )
+
 The headers you pass to ``vary_on_headers`` are not case sensitive;
 ``"User-Agent"`` is the same thing as ``"user-agent"``.
 

tests/regressiontests/cache/tests.py

@@ -4 +4 @@
 # Uses whatever cache backend is set in the test settings file.
 
 import os
+import re
 import shutil
 import tempfile
 import time
@@ -298 +299 @@
         self.path = '/cache/test/'
         self.old_settings_key_prefix = settings.CACHE_MIDDLEWARE_KEY_PREFIX
         self.old_middleware_seconds = settings.CACHE_MIDDLEWARE_SECONDS
+        self.old_ignore_cookies = settings.CACHE_MIDDLEWARE_IGNORE_COOKIES
         settings.CACHE_MIDDLEWARE_KEY_PREFIX = 'settingsprefix'
         settings.CACHE_MIDDLEWARE_SECONDS = 1
+        settings.CACHE_MIDDLEWARE_IGNORE_COOKIES = ( re.compile(r'^testcookie$'), )
 
     def tearDown(self):
         settings.CACHE_MIDDLEWARE_KEY_PREFIX = self.old_settings_key_prefix
         settings.CACHE_MIDDLEWARE_SECONDS = self.old_middleware_seconds
+        settings.CACHE_MIDDLEWARE_IGNORE_COOKIES = self.old_ignore_cookies
 
     def _get_request(self, path):
         request = HttpRequest()
@@ -355 +359 @@
         learn_cache_key(request, response)
         self.assertEqual(get_cache_key(request), 'views.decorators.cache.cache_page.settingsprefix.a8c87a3d8c44853d7f79474f7ffe4ad5.d41d8cd98f00b204e9800998ecf8427e')
 
+    def test_ignore_cookies(self):
+        request = self._get_request(self.path)
+        response = HttpResponse()
+        response['Vary'] = 'Cookie'
+        learn_cache_key(request, response)
+        # Set request cookies not matched in CACHE_MIDDLEWARE_IGNORE_COOKIES
+        request.COOKIES = { 'foo': 1, 'bar': 2 }
+        self.assertEqual(get_cache_key(request), 'views.decorators.cache.cache_page.settingsprefix.a8c87a3d8c44853d7f79474f7ffe4ad5.b4cb935fc7540cefaa961599c74eab3d')
+        request.COOKIES = { 'foo': 1, 'bar': 2, 'testcookie': 'value' }
+        # Ensure same key as without ignored cookie
+        self.assertEqual(get_cache_key(request), 'views.decorators.cache.cache_page.settingsprefix.a8c87a3d8c44853d7f79474f7ffe4ad5.b4cb935fc7540cefaa961599c74eab3d')
+        request.COOKIES = { }
+        self.assertEqual(get_cache_key(request), 'views.decorators.cache.cache_page.settingsprefix.a8c87a3d8c44853d7f79474f7ffe4ad5.d41d8cd98f00b204e9800998ecf8427e')
+
 if __name__ == '__main__':
     unittest.main()