Reduced CookieStorage.max_cookie_size to 75% of 4K to be nice to Internet Explorer

Internet Explorer, up to at least version 7, allows only 4K cookie data *per
domain*, rather than per cookie, so we ensure that stored messages leave
some room for other cookies.




git-svn-id: http://code.djangoproject.com/svn/django/trunk@12287 bcc190cf-cafb-0310-a4f2-bffc1f526a37

django/contrib/messages/storage/cookie.py

@@ -1,10 +1,11 @@
 import hmac
 
 from django.conf import settings
-from django.utils.hashcompat import sha_hmac
 from django.contrib.messages import constants
 from django.contrib.messages.storage.base import BaseStorage, Message
+from django.http import CompatCookie
 from django.utils import simplejson as json
+from django.utils.hashcompat import sha_hmac
 
 
 class MessageEncoder(json.JSONEncoder):
@@ -46,7 +47,10 @@ class CookieStorage(BaseStorage):
     Stores messages in a cookie.
     """
     cookie_name = 'messages'
-    max_cookie_size = 4096
+    # We should be able to store 4K in a cookie, but Internet Explorer
+    # imposes 4K as the *total* limit for a domain.  To allow other
+    # cookies, we go for 3/4 of 4K.
+    max_cookie_size = 3072
     not_finished = '__messagesnotfinished__'
 
     def _get(self, *args, **kwargs):

django/contrib/messages/tests/cookie.py

@@ -69,19 +69,25 @@ class CookieTest(BaseTest):
         storage = self.get_storage()
         response = self.get_response()
 
+        # When storing as a cookie, the cookie has constant overhead of approx
+        # 54 chars, and each message has a constant overhead of about 37 chars
+        # and a variable overhead of zero in the best case. We aim for a message
+        # size which will fit 4 messages into the cookie, but not 5.
+        # See also FallbackTest.test_session_fallback
+        msg_size = int((CookieStorage.max_cookie_size - 54) / 4.5 - 37)
         for i in range(5):
-            storage.add(constants.INFO, str(i) * 900)
+            storage.add(constants.INFO, str(i) * msg_size)
         unstored_messages = storage.update(response)
 
         cookie_storing = self.stored_messages_count(storage, response)
         self.assertEqual(cookie_storing, 4)
 
         self.assertEqual(len(unstored_messages), 1)
-        self.assert_(unstored_messages[0].message == '0' * 900)
+        self.assert_(unstored_messages[0].message == '0' * msg_size)
 
     def test_json_encoder_decoder(self):
         """
-        Tests that an complex nested data structure containing Message
+        Tests that a complex nested data structure containing Message
         instances is properly encoded/decoded by the custom JSON
         encoder/decoder classes.
         """

django/contrib/messages/tests/fallback.py

@@ -147,8 +147,10 @@ class FallbackTest(BaseTest):
         storage = self.get_storage()
         response = self.get_response()
 
+        # see comment in CookieText.test_cookie_max_length
+        msg_size = int((CookieStorage.max_cookie_size - 54) / 4.5 - 37)
         for i in range(5):
-            storage.add(constants.INFO, str(i) * 900)
+            storage.add(constants.INFO, str(i) * msg_size)
         storage.update(response)
 
         cookie_storing = self.stored_cookie_messages_count(storage, response)