Fixed #9595 -- Allow non-expiring cache timeouts.

Also, streamline the use of 0 and None between cache backends.

AUTHORS

@@ -123,6 +123,7 @@ answer newbie questions, and generally made Django that much better:
     bthomas
     btoll@bestweb.net
     Jonathan Buchanan <jonathan.buchanan@gmail.com>
+    Jacob Burch <jacobburch@gmail.com>
     Keith Bussell <kbussell@gmail.com>
     C8E
     Chris Cahoon <chris.cahoon@gmail.com>

django/core/cache/backends/base.py

@@ -15,6 +15,10 @@ class CacheKeyWarning(DjangoRuntimeWarning):
     pass
 
 
+# Stub class to ensure not passing in a `timeout` argument results in
+# the default timeout
+DEFAULT_TIMEOUT = object()
+
 # Memcached does not accept keys longer than this.
 MEMCACHE_MAX_KEY_LENGTH = 250
 
@@ -84,7 +88,7 @@ class BaseCache(object):
         new_key = self.key_func(key, self.key_prefix, version)
         return new_key
 
-    def add(self, key, value, timeout=None, version=None):
+    def add(self, key, value, timeout=DEFAULT_TIMEOUT, version=None):
         """
         Set a value in the cache if the key does not already exist. If
         timeout is given, that timeout will be used for the key; otherwise
@@ -101,7 +105,7 @@ class BaseCache(object):
         """
         raise NotImplementedError
 
-    def set(self, key, value, timeout=None, version=None):
+    def set(self, key, value, timeout=DEFAULT_TIMEOUT, version=None):
         """
         Set a value in the cache. If timeout is given, that timeout will be
         used for the key; otherwise the default cache timeout will be used.
@@ -163,7 +167,7 @@ class BaseCache(object):
         # if a subclass overrides it.
         return self.has_key(key)
 
-    def set_many(self, data, timeout=None, version=None):
+    def set_many(self, data, timeout=DEFAULT_TIMEOUT, version=None):
         """
         Set a bunch of values in the cache at once from a dict of key/value
         pairs.  For certain backends (memcached), this is much more efficient

django/core/cache/backends/db.py

@@ -9,7 +9,7 @@ except ImportError:
     import pickle
 
 from django.conf import settings
-from django.core.cache.backends.base import BaseCache
+from django.core.cache.backends.base import BaseCache, DEFAULT_TIMEOUT
 from django.db import connections, transaction, router, DatabaseError
 from django.utils import timezone, six
 from django.utils.encoding import force_bytes
@@ -65,6 +65,7 @@ class DatabaseCache(BaseDatabaseCache):
         if row is None:
             return default
         now = timezone.now()
+
         if row[2] < now:
             db = router.db_for_write(self.cache_model_class)
             cursor = connections[db].cursor()
@@ -74,18 +75,18 @@ class DatabaseCache(BaseDatabaseCache):
         value = connections[db].ops.process_clob(row[1])
         return pickle.loads(base64.b64decode(force_bytes(value)))
 
-    def set(self, key, value, timeout=None, version=None):
+    def set(self, key, value, timeout=DEFAULT_TIMEOUT, version=None):
         key = self.make_key(key, version=version)
         self.validate_key(key)
         self._base_set('set', key, value, timeout)
 
-    def add(self, key, value, timeout=None, version=None):
+    def add(self, key, value, timeout=DEFAULT_TIMEOUT, version=None):
         key = self.make_key(key, version=version)
         self.validate_key(key)
         return self._base_set('add', key, value, timeout)
 
-    def _base_set(self, mode, key, value, timeout=None):
+    def _base_set(self, mode, key, value, timeout=DEFAULT_TIMEOUT):
-        if timeout is None:
+        if timeout == DEFAULT_TIMEOUT:
             timeout = self.default_timeout
         db = router.db_for_write(self.cache_model_class)
         table = connections[db].ops.quote_name(self._table)
@@ -95,7 +96,9 @@ class DatabaseCache(BaseDatabaseCache):
         num = cursor.fetchone()[0]
         now = timezone.now()
         now = now.replace(microsecond=0)
-        if settings.USE_TZ:
+        if timeout is None:
+            exp = datetime.max
+        elif settings.USE_TZ:
             exp = datetime.utcfromtimestamp(time.time() + timeout)
         else:
             exp = datetime.fromtimestamp(time.time() + timeout)

django/core/cache/backends/dummy.py

@@ -1,12 +1,12 @@
 "Dummy cache backend"
 
-from django.core.cache.backends.base import BaseCache
+from django.core.cache.backends.base import BaseCache, DEFAULT_TIMEOUT
 
 class DummyCache(BaseCache):
     def __init__(self, host, *args, **kwargs):
         BaseCache.__init__(self, *args, **kwargs)
 
-    def add(self, key, value, timeout=None, version=None):
+    def add(self, key, value, timeout=DEFAULT_TIMEOUT, version=None):
         key = self.make_key(key, version=version)
         self.validate_key(key)
         return True
@@ -16,7 +16,7 @@ class DummyCache(BaseCache):
         self.validate_key(key)
         return default
 
-    def set(self, key, value, timeout=None, version=None):
+    def set(self, key, value, timeout=DEFAULT_TIMEOUT, version=None):
         key = self.make_key(key, version=version)
         self.validate_key(key)
 
@@ -32,7 +32,7 @@ class DummyCache(BaseCache):
         self.validate_key(key)
         return False
 
-    def set_many(self, data, timeout=0, version=None):
+    def set_many(self, data, timeout=DEFAULT_TIMEOUT, version=None):
         pass
 
     def delete_many(self, keys, version=None):

django/core/cache/backends/filebased.py

@@ -9,9 +9,10 @@ try:
 except ImportError:
     import pickle
 
-from django.core.cache.backends.base import BaseCache
+from django.core.cache.backends.base import BaseCache, DEFAULT_TIMEOUT
 from django.utils.encoding import force_bytes
 
+
 class FileBasedCache(BaseCache):
     def __init__(self, dir, params):
         BaseCache.__init__(self, params)
@@ -19,7 +20,7 @@ class FileBasedCache(BaseCache):
         if not os.path.exists(self._dir):
             self._createdir()
 
-    def add(self, key, value, timeout=None, version=None):
+    def add(self, key, value, timeout=DEFAULT_TIMEOUT, version=None):
         if self.has_key(key, version=version):
             return False
 
@@ -35,7 +36,7 @@ class FileBasedCache(BaseCache):
             with open(fname, 'rb') as f:
                 exp = pickle.load(f)
                 now = time.time()
-                if exp < now:
+                if exp is not None and exp < now:
                     self._delete(fname)
                 else:
                     return pickle.load(f)
@@ -43,14 +44,14 @@ class FileBasedCache(BaseCache):
             pass
         return default
 
-    def set(self, key, value, timeout=None, version=None):
+    def set(self, key, value, timeout=DEFAULT_TIMEOUT, version=None):
         key = self.make_key(key, version=version)
         self.validate_key(key)
 
         fname = self._key_to_file(key)
         dirname = os.path.dirname(fname)
 
-        if timeout is None:
+        if timeout == DEFAULT_TIMEOUT:
             timeout = self.default_timeout
 
         self._cull()
@@ -60,8 +61,8 @@ class FileBasedCache(BaseCache):
                 os.makedirs(dirname)
 
             with open(fname, 'wb') as f:
-                now = time.time()
+                expiry = None if timeout is None else time.time() + timeout
-                pickle.dump(now + timeout, f, pickle.HIGHEST_PROTOCOL)
+                pickle.dump(expiry, f, pickle.HIGHEST_PROTOCOL)
                 pickle.dump(value, f, pickle.HIGHEST_PROTOCOL)
         except (IOError, OSError):
             pass

django/core/cache/backends/locmem.py

@@ -6,7 +6,7 @@ try:
 except ImportError:
     import pickle
 
-from django.core.cache.backends.base import BaseCache
+from django.core.cache.backends.base import BaseCache, DEFAULT_TIMEOUT
 from django.utils.synch import RWLock
 
 # Global in-memory store of cache data. Keyed by name, to provide
@@ -23,7 +23,7 @@ class LocMemCache(BaseCache):
         self._expire_info = _expire_info.setdefault(name, {})
         self._lock = _locks.setdefault(name, RWLock())
 
-    def add(self, key, value, timeout=None, version=None):
+    def add(self, key, value, timeout=DEFAULT_TIMEOUT, version=None):
         key = self.make_key(key, version=version)
         self.validate_key(key)
         with self._lock.writer():
@@ -41,10 +41,8 @@ class LocMemCache(BaseCache):
         key = self.make_key(key, version=version)
         self.validate_key(key)
         with self._lock.reader():
-            exp = self._expire_info.get(key)
+            exp = self._expire_info.get(key, 0)
-            if exp is None:
+            if exp is None or exp > time.time():
-                return default
-            elif exp > time.time():
                 try:
                     pickled = self._cache[key]
                     return pickle.loads(pickled)
@@ -58,15 +56,16 @@ class LocMemCache(BaseCache):
                 pass
             return default
 
-    def _set(self, key, value, timeout=None):
+    def _set(self, key, value, timeout=DEFAULT_TIMEOUT):
         if len(self._cache) >= self._max_entries:
             self._cull()
-        if timeout is None:
+        if timeout == DEFAULT_TIMEOUT:
             timeout = self.default_timeout
+        expiry = None if timeout is None else time.time() + timeout
         self._cache[key] = value
-        self._expire_info[key] = time.time() + timeout
+        self._expire_info[key] = expiry
 
-    def set(self, key, value, timeout=None, version=None):
+    def set(self, key, value, timeout=DEFAULT_TIMEOUT, version=None):
         key = self.make_key(key, version=version)
         self.validate_key(key)
         with self._lock.writer():

django/core/cache/backends/memcached.py

@@ -4,7 +4,7 @@ import time
 import pickle
 from threading import local
 
-from django.core.cache.backends.base import BaseCache, InvalidCacheBackendError
+from django.core.cache.backends.base import BaseCache, DEFAULT_TIMEOUT
 
 from django.utils import six
 from django.utils.encoding import force_str
@@ -36,12 +36,22 @@ class BaseMemcachedCache(BaseCache):
 
         return self._client
 
-    def _get_memcache_timeout(self, timeout):
+    def _get_memcache_timeout(self, timeout=DEFAULT_TIMEOUT):
         """
         Memcached deals with long (> 30 days) timeouts in a special
         way. Call this function to obtain a safe value for your timeout.
         """
-        timeout = timeout or self.default_timeout
+        if timeout == DEFAULT_TIMEOUT:
+            return self.default_timeout
+
+        if timeout is None:
+            # Using 0 in memcache sets a non-expiring timeout.
+            return 0
+        elif int(timeout) == 0:
+            # Other cache backends treat 0 as set-and-expire. To achieve this
+            # in memcache backends, a negative timeout must be passed.
+            timeout = -1
+
         if timeout > 2592000: # 60*60*24*30, 30 days
             # See http://code.google.com/p/memcached/wiki/FAQ
             # "You can set expire times up to 30 days in the future. After that
@@ -56,7 +66,7 @@ class BaseMemcachedCache(BaseCache):
         # Python 2 memcache requires the key to be a byte string.
         return force_str(super(BaseMemcachedCache, self).make_key(key, version))
 
-    def add(self, key, value, timeout=0, version=None):
+    def add(self, key, value, timeout=DEFAULT_TIMEOUT, version=None):
         key = self.make_key(key, version=version)
         return self._cache.add(key, value, self._get_memcache_timeout(timeout))
 
@@ -67,7 +77,7 @@ class BaseMemcachedCache(BaseCache):
             return default
         return val
 
-    def set(self, key, value, timeout=0, version=None):
+    def set(self, key, value, timeout=DEFAULT_TIMEOUT, version=None):
         key = self.make_key(key, version=version)
         self._cache.set(key, value, self._get_memcache_timeout(timeout))
 
@@ -125,7 +135,7 @@ class BaseMemcachedCache(BaseCache):
             raise ValueError("Key '%s' not found" % key)
         return val
 
-    def set_many(self, data, timeout=0, version=None):
+    def set_many(self, data, timeout=DEFAULT_TIMEOUT, version=None):
         safe_data = {}
         for key, value in data.items():
             key = self.make_key(key, version=version)

docs/releases/1.6.txt

@@ -485,6 +485,12 @@ Miscellaneous
   changes in 1.6 particularly affect :class:`~django.forms.DecimalField` and
   :class:`~django.forms.ModelMultipleChoiceField`.
 
+* There have been changes in the way timeouts are handled in cache backends.
+  Explicitly passing in ``timeout=None`` no longer results in using the
+  default timeout. It will now set a non-expiring timeout. Passing 0 into the
+  memcache backend no longer uses the default timeout, and now will
+  set-and-expire-immediately the value.
+
 Features deprecated in 1.6
 ==========================
 

docs/topics/cache.txt

@@ -707,10 +707,15 @@ The basic interface is ``set(key, value, timeout)`` and ``get(key)``::
     >>> cache.get('my_key')
     'hello, world!'
 
-The ``timeout`` argument is optional and defaults to the ``timeout``
+The ``timeout`` argument is optional and defaults to the ``timeout`` argument
-argument of the appropriate backend in the :setting:`CACHES` setting
+of the appropriate backend in the :setting:`CACHES` setting (explained above).
-(explained above). It's the number of seconds the value should be stored
+It's the number of seconds the value should be stored in the cache. Passing in
-in the cache.
+``None`` for ``timeout`` will cache the value forever.
+
+.. versionchanged:: 1.6
+
+    Previously, passing ``None`` explicitly would use the default timeout
+    value.
 
 If the object doesn't exist in the cache, ``cache.get()`` returns ``None``::
 

tests/cache/tests.py

@@ -441,6 +441,34 @@ class BaseCacheTests(object):
         self.assertEqual(self.cache.get('key3'), 'sausage')
         self.assertEqual(self.cache.get('key4'), 'lobster bisque')
 
+    def test_forever_timeout(self):
+        '''
+        Passing in None into timeout results in a value that is cached forever
+        '''
+        self.cache.set('key1', 'eggs', None)
+        self.assertEqual(self.cache.get('key1'), 'eggs')
+
+        self.cache.add('key2', 'ham', None)
+        self.assertEqual(self.cache.get('key2'), 'ham')
+
+        self.cache.set_many({'key3': 'sausage', 'key4': 'lobster bisque'}, None)
+        self.assertEqual(self.cache.get('key3'), 'sausage')
+        self.assertEqual(self.cache.get('key4'), 'lobster bisque')
+
+    def test_zero_timeout(self):
+        '''
+        Passing in None into timeout results in a value that is cached forever
+        '''
+        self.cache.set('key1', 'eggs', 0)
+        self.assertEqual(self.cache.get('key1'), None)
+
+        self.cache.add('key2', 'ham', 0)
+        self.assertEqual(self.cache.get('key2'), None)
+
+        self.cache.set_many({'key3': 'sausage', 'key4': 'lobster bisque'}, 0)
+        self.assertEqual(self.cache.get('key3'), None)
+        self.assertEqual(self.cache.get('key4'), None)
+
     def test_float_timeout(self):
         # Make sure a timeout given as a float doesn't crash anything.
         self.cache.set("key1", "spam", 100.2)