Fixed #21012 -- Thread-local caches, like databases.

django/contrib/sessions/backends/cache.py

@@ -1,6 +1,6 @@
 from django.conf import settings
 from django.contrib.sessions.backends.base import SessionBase, CreateError
-from django.core.cache import get_cache
+from django.core.cache import caches
 from django.utils.six.moves import xrange
 
 KEY_PREFIX = "django.contrib.sessions.cache"
@@ -11,7 +11,7 @@ class SessionStore(SessionBase):
     A cache-based session store.
     """
     def __init__(self, session_key=None):
-        self._cache = get_cache(settings.SESSION_CACHE_ALIAS)
+        self._cache = caches[settings.SESSION_CACHE_ALIAS]
         super(SessionStore, self).__init__(session_key)
 
     @property

django/contrib/sessions/backends/cached_db.py

@@ -6,7 +6,7 @@ import logging
 
 from django.conf import settings
 from django.contrib.sessions.backends.db import SessionStore as DBStore
-from django.core.cache import get_cache
+from django.core.cache import caches
 from django.core.exceptions import SuspiciousOperation
 from django.utils import timezone
 from django.utils.encoding import force_text
@@ -20,7 +20,7 @@ class SessionStore(DBStore):
     """
 
     def __init__(self, session_key=None):
-        self._cache = get_cache(settings.SESSION_CACHE_ALIAS)
+        self._cache = caches[settings.SESSION_CACHE_ALIAS]
         super(SessionStore, self).__init__(session_key)
 
     @property

django/contrib/sessions/tests.py

@@ -15,7 +15,7 @@ from django.contrib.sessions.backends.file import SessionStore as FileSession
 from django.contrib.sessions.backends.signed_cookies import SessionStore as CookieSession
 from django.contrib.sessions.models import Session
 from django.contrib.sessions.middleware import SessionMiddleware
-from django.core.cache import get_cache
+from django.core.cache import caches
 from django.core.cache.backends.base import InvalidCacheBackendError
 from django.core import management
 from django.core.exceptions import ImproperlyConfigured
@@ -140,7 +140,7 @@ class SessionTestsMixin(object):
         self.assertTrue(self.session.modified)
 
     def test_save(self):
-        if (hasattr(self.session, '_cache') and'DummyCache' in
+        if (hasattr(self.session, '_cache') and 'DummyCache' in
             settings.CACHES[settings.SESSION_CACHE_ALIAS]['BACKEND']):
             raise unittest.SkipTest("Session saving tests require a real cache backend")
         self.session.save()
@@ -481,7 +481,7 @@ class CacheSessionTests(SessionTestsMixin, unittest.TestCase):
 
     def test_default_cache(self):
         self.session.save()
-        self.assertNotEqual(get_cache('default').get(self.session.cache_key), None)
+        self.assertNotEqual(caches['default'].get(self.session.cache_key), None)
 
     @override_settings(CACHES={
         'default': {
@@ -489,6 +489,7 @@ class CacheSessionTests(SessionTestsMixin, unittest.TestCase):
         },
         'sessions': {
             'BACKEND': 'django.core.cache.backends.locmem.LocMemCache',
+            'LOCATION': 'session',
         },
     }, SESSION_CACHE_ALIAS='sessions')
     def test_non_default_cache(self):
@@ -496,8 +497,8 @@ class CacheSessionTests(SessionTestsMixin, unittest.TestCase):
         self.session = self.backend()
 
         self.session.save()
-        self.assertEqual(get_cache('default').get(self.session.cache_key), None)
-        self.assertNotEqual(get_cache('sessions').get(self.session.cache_key), None)
+        self.assertEqual(caches['default'].get(self.session.cache_key), None)
+        self.assertNotEqual(caches['sessions'].get(self.session.cache_key), None)
 
 
 class SessionMiddlewareTests(unittest.TestCase):

django/contrib/staticfiles/storage.py

@@ -7,7 +7,7 @@ import posixpath
 import re
 
 from django.conf import settings
-from django.core.cache import (get_cache, InvalidCacheBackendError,
+from django.core.cache import (caches, InvalidCacheBackendError,
                                cache as default_cache)
 from django.core.exceptions import ImproperlyConfigured
 from django.core.files.base import ContentFile
@@ -56,7 +56,7 @@ class CachedFilesMixin(object):
     def __init__(self, *args, **kwargs):
         super(CachedFilesMixin, self).__init__(*args, **kwargs)
         try:
-            self.cache = get_cache('staticfiles')
+            self.cache = caches['staticfiles']
         except InvalidCacheBackendError:
             # Use the default backend
             self.cache = default_cache

django/core/cache/__init__.py

@@ -14,6 +14,9 @@ class.
 
 See docs/topics/cache.txt for information on the public API.
 """
+from threading import local
+import warnings
+
 from django.conf import settings
 from django.core import signals
 from django.core.cache.backends.base import (
@@ -23,8 +26,8 @@ from django.utils.module_loading import import_by_path
 
 
 __all__ = [
-    'get_cache', 'cache', 'DEFAULT_CACHE_ALIAS', 'InvalidCacheBackendError',
-    'CacheKeyWarning', 'BaseCache',
+    'create_cache', 'get_cache', 'cache', 'DEFAULT_CACHE_ALIAS',
+    'InvalidCacheBackendError', 'CacheKeyWarning', 'BaseCache',
 ]
 
 DEFAULT_CACHE_ALIAS = 'default'
@@ -35,43 +38,61 @@ if DEFAULT_CACHE_ALIAS not in settings.CACHES:
 
 def get_cache(backend, **kwargs):
     """
-    Function to load a cache backend dynamically. This is flexible by design
-    to allow different use cases:
+    Function to retrieve a configure cache, or create a new one.
 
-    To load a backend that is pre-defined in the settings::
+    This wrapper is for backward compatibility.
 
-        cache = get_cache('default')
-
-    To load a backend with its dotted import path,
-    including arbitrary options::
-
-        cache = get_cache('django.core.cache.backends.memcached.MemcachedCache', **{
-            'LOCATION': '127.0.0.1:11211', 'TIMEOUT': 30,
-        })
+    Use either create_cache or caches directly.
 
     """
+    warnings.warn("'get_cache' is deprecated.  Use either caches or create_cache.",
+        PendingDeprecationWarning, stacklevel=2)
+
+    # If it's just an alias with no options, use the new API
+    if backend in settings.CACHES and not kwargs:
+        return caches[backend]
+
+    return create_cache(backend, **kwargs)
+
+
+def create_cache(backend, **params):
+    """
+    Function to create a cache backend dynamically.  This is flexible by design
+    to allow different use cases:
+
+    To load a backend with its dotted import path, including options::
+
+        cache = get_cache('django.core.cache.backends.memcached.MemcachedCache',
+            LOCATION='127.0.0.1:11211', TIMEOUT=30,
+        })
+
+    To create a new instance of a cache in settings.CACHES, pass the alias::
+
+        cache = create_cache('default')
+
+    You can also pass extra parameters to override those in settings.CACHES::
+
+        cache = create_cache('default', LOCATION='bar')
+
+    """
+
+    # We can name a cache from settings.CACHES and update its params
+    try:
+        conf = settings.CACHES[backend]
+    except KeyError:
+        pass
+    else:
+        params = conf.copy()
+        params.update(params)
+        backend = params.pop('BACKEND')
+
     try:
-        # Try to get the CACHES entry for the given backend name first
-        try:
-            conf = settings.CACHES[backend]
-        except KeyError:
-            try:
-                # Trying to import the given backend, in case it's a dotted path
-                import_by_path(backend)
-            except ImproperlyConfigured as e:
-                raise InvalidCacheBackendError("Could not find backend '%s': %s" % (
-                    backend, e))
-            location = kwargs.pop('LOCATION', '')
-            params = kwargs
-        else:
-            params = conf.copy()
-            params.update(kwargs)
-            backend = params.pop('BACKEND')
-            location = params.pop('LOCATION', '')
         backend_cls = import_by_path(backend)
-    except (AttributeError, ImportError, ImproperlyConfigured) as e:
-        raise InvalidCacheBackendError(
-            "Could not find backend '%s': %s" % (backend, e))
+    except ImproperlyConfigured as e:
+        raise InvalidCacheBackendError("Could not find backend '%s': %s" % (
+            backend, e
+        ))
+    location = params.pop('LOCATION', '')
     cache = backend_cls(location, params)
     # Some caches -- python-memcached in particular -- need to do a cleanup at the
     # end of a request cycle. If not implemented in a particular backend
@@ -79,4 +100,54 @@ def get_cache(backend, **kwargs):
     signals.request_finished.connect(cache.close)
     return cache
 
-cache = get_cache(DEFAULT_CACHE_ALIAS)
+
+class CacheHandler(object):
+    """
+    A Cache Handler to manage access to Cache instances.
+
+    Ensures only one instance of each alias exists per thread.
+    """
+    def __init__(self):
+        self._caches = local()
+
+    def __getitem__(self, alias):
+        try:
+            return getattr(self._caches, alias)
+        except AttributeError:
+            pass
+
+        if alias not in settings.CACHES:
+            raise InvalidCacheBackendError(
+                "Could not find config for '%s' in settings.CACHES" % alias
+            )
+
+        cache = create_cache(alias)
+        setattr(self._caches, alias, cache)
+
+        return cache
+
+caches = CacheHandler()
+
+class DefaultCacheProxy(object):
+    """
+    Proxy access to the default Cache object's attributes.
+
+    This allows the legacy `cache` object to be thread-safe using the new
+    ``caches`` API.
+    """
+    def __getattr__(self, name):
+        return getattr(caches[DEFAULT_CACHE_ALIAS], name)
+
+    def __setattr__(self, name, value):
+        return setattr(caches[DEFAULT_CACHE_ALIAS], name, value)
+
+    def __delattr__(self, name):
+        return delattr(caches[DEFAULT_CACHE_ALIAS], name)
+
+    def __eq__(self, other):
+        return caches[DEFAULT_CACHE_ALIAS] == other
+
+    def __ne__(self, other):
+        return caches[DEFAULT_CACHE_ALIAS] != other
+
+cache = DefaultCacheProxy()

django/core/cache/backends/memcached.py

@@ -2,13 +2,13 @@
 
 import time
 import pickle
-from threading import local
 
 from django.core.cache.backends.base import BaseCache, DEFAULT_TIMEOUT
 
 from django.utils import six
 from django.utils.deprecation import RenameMethodsBase
 from django.utils.encoding import force_str
+from django.utils.functional import cached_property
 
 
 class BaseMemcachedCacheMethods(RenameMethodsBase):
@@ -177,24 +177,14 @@ class PyLibMCCache(BaseMemcachedCache):
     "An implementation of a cache binding using pylibmc"
     def __init__(self, server, params):
         import pylibmc
-        self._local = local()
         super(PyLibMCCache, self).__init__(server, params,
                                            library=pylibmc,
                                            value_not_found_exception=pylibmc.NotFound)
 
-    @property
+    @cached_property
     def _cache(self):
-        # PylibMC uses cache options as the 'behaviors' attribute.
-        # It also needs to use threadlocals, because some versions of
-        # PylibMC don't play well with the GIL.
-        client = getattr(self._local, 'client', None)
-        if client:
-            return client
-
         client = self._lib.Client(self._servers)
         if self._options:
             client.behaviors = self._options
 
-        self._local.client = client
-
         return client

django/core/management/commands/createcachetable.py

@@ -1,7 +1,7 @@
 from optparse import make_option
 
 from django.conf import settings
-from django.core.cache import get_cache
+from django.core.cache import create_cache
 from django.core.cache.backends.db import BaseDatabaseCache
 from django.core.management.base import BaseCommand, CommandError
 from django.db import connections, router, transaction, models, DEFAULT_DB_ALIAS
@@ -30,7 +30,7 @@ class Command(BaseCommand):
                 self.create_table(db, tablename)
         else:
             for cache_alias in settings.CACHES:
-                cache = get_cache(cache_alias)
+                cache = create_cache(cache_alias)
                 if isinstance(cache, BaseDatabaseCache):
                     self.create_table(db, cache._table)
 

django/middleware/cache.py

@@ -46,7 +46,7 @@ More details about how the caching works:
 import warnings
 
 from django.conf import settings
-from django.core.cache import get_cache, DEFAULT_CACHE_ALIAS
+from django.core.cache import create_cache, caches, DEFAULT_CACHE_ALIAS
 from django.utils.cache import get_cache_key, learn_cache_key, patch_response_headers, get_max_age
 
 
@@ -64,7 +64,7 @@ class UpdateCacheMiddleware(object):
         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)
+        self.cache = caches[self.cache_alias]
 
     def _session_accessed(self, request):
         try:
@@ -122,10 +122,9 @@ class FetchFromCacheMiddleware(object):
     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_alias = settings.CACHE_MIDDLEWARE_ALIAS
-        self.cache = get_cache(self.cache_alias)
+        self.cache = caches[self.cache_alias]
 
     def process_request(self, request):
         """
@@ -169,39 +168,32 @@ class CacheMiddleware(UpdateCacheMiddleware, FetchFromCacheMiddleware):
         # we fall back to system defaults. If it is not provided at all,
         # we need to use middleware defaults.
 
-        cache_kwargs = {}
+        try:
+            key_prefix = kwargs['key_prefix']
+            if key_prefix is None:
+                key_prefix = ''
+        except KeyError:
+            key_prefix = settings.CACHE_MIDDLEWARE_KEY_PREFIX
+        self.key_prefix = key_prefix
 
         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 = ''
+            cache_alias = kwargs['cache_alias']
+            if cache_alias is None:
+                cache_alias = DEFAULT_CACHE_ALIAS
         except KeyError:
-            self.key_prefix = settings.CACHE_MIDDLEWARE_KEY_PREFIX
-            cache_kwargs['KEY_PREFIX'] = self.key_prefix
+            cache_alias = settings.CACHE_MIDDLEWARE_ALIAS
+        self.cache_alias = cache_alias
 
-        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_timeout is None:
+            cache_timeout = settings.CACHE_MIDDLEWARE_SECONDS
+        self.cache_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
+            cache_anonymous_only = getattr(settings, 'CACHE_MIDDLEWARE_ANONYMOUS_ONLY', False)
+        self.cache_anonymous_only = cache_anonymous_only
 
         if self.cache_anonymous_only:
             msg = "CACHE_MIDDLEWARE_ANONYMOUS_ONLY has been deprecated and will be removed in Django 1.8."
             warnings.warn(msg, DeprecationWarning, stacklevel=1)
 
-        self.cache = get_cache(self.cache_alias, **cache_kwargs)
-        self.cache_timeout = self.cache.default_timeout
+        self.cache = create_cache(self.cache_alias)

django/templatetags/cache.py

@@ -1,13 +1,13 @@
 from __future__ import unicode_literals
 
-from django.core.cache import get_cache, InvalidCacheBackendError
+from django.core.cache import caches, InvalidCacheBackendError
 from django.core.cache.utils import make_template_fragment_key
 from django.template import Library, Node, TemplateSyntaxError, VariableDoesNotExist
 
 register = Library()
 
 try:
-    default_cache = get_cache('template_fragments')
+    default_cache = caches['template_fragments']
 except InvalidCacheBackendError:
     from django.core.cache import cache as default_cache
 
@@ -35,7 +35,7 @@ class CacheNode(Node):
             except VariableDoesNotExist:
                 raise TemplateSyntaxError('"cache" tag got an unknown variable: %r' % self.cache_name.var)
             try:
-                cache = get_cache(cache_name)
+                cache = caches[cache_name]
             except InvalidCacheBackendError:
                 raise TemplateSyntaxError('Invalid cache name specified for cache tag: %r' % cache_name)
         else:

django/utils/cache.py

@@ -23,7 +23,7 @@ import re
 import time
 
 from django.conf import settings
-from django.core.cache import get_cache
+from django.core.cache import caches
 from django.utils.encoding import iri_to_uri, force_bytes, force_text
 from django.utils.http import http_date
 from django.utils.timezone import get_current_timezone_name
@@ -219,7 +219,7 @@ def get_cache_key(request, key_prefix=None, method='GET', cache=None):
         key_prefix = settings.CACHE_MIDDLEWARE_KEY_PREFIX
     cache_key = _generate_cache_header_key(key_prefix, request)
     if cache is None:
-        cache = get_cache(settings.CACHE_MIDDLEWARE_ALIAS)
+        cache = caches[settings.CACHE_MIDDLEWARE_ALIAS]
     headerlist = cache.get(cache_key, None)
     if headerlist is not None:
         return _generate_cache_key(request, method, headerlist, key_prefix)
@@ -246,7 +246,7 @@ def learn_cache_key(request, response, cache_timeout=None, key_prefix=None, cach
         cache_timeout = settings.CACHE_MIDDLEWARE_SECONDS
     cache_key = _generate_cache_header_key(key_prefix, request)
     if cache is None:
-        cache = get_cache(settings.CACHE_MIDDLEWARE_ALIAS)
+        cache = caches[settings.CACHE_MIDDLEWARE_ALIAS]
     if response.has_header('Vary'):
         is_accept_language_redundant = settings.USE_I18N or settings.USE_L10N
         # If i18n or l10n are used, the generated cache key will be suffixed

docs/internals/deprecation.txt

@@ -215,6 +215,9 @@ these changes.
 
 * The internal ``django.utils.functional.memoize`` will be removed.
 
+* ``get_cache`` from django.core.cache will be removed.  Instead, use
+  ``create_cache`` or  ``caches``, depending on your need.
+
 2.0
 ---
 

docs/releases/1.7.txt

@@ -269,6 +269,26 @@ Minor features
   allowing the ``published`` element to be included in the feed (which
   relies on ``pubdate``).
 
+Cache
+^^^^^
+
+* Access to caches configured in ``settings.CACHES`` is now available via
+  ``django.core.cache.caches``.  This will now return a different instance per
+  thread.
+
+* A new function ``django.core.cache.create_cache`` has been added to make it
+  clearer what's happening.  ``django.core.cache.get_cache`` will call this
+  if it's passed anything other than just a cache config alias.
+
+* ``django.core.cache.get_cache`` has been deprecated.  Use
+  ``django.core.cache.caches`` to access caches configurd in
+  ``settings.CACHES``, or ``django.core.cache.create_cache`` to create ad-hoc
+  instances.
+
+* All thread safety in cache backends has been removed, as
+  ``django.core.cache.caches`` now yields differend backend instances per
+   thread.
+
 Email
 ^^^^^
 
@@ -643,6 +663,12 @@ Miscellaneous
 Features deprecated in 1.7
 ==========================
 
+``django.core.cache.get_cache``
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+``django.core.cache.get_cache`` has been supplanted by
+``django.core.cache.caches`` and ``django.core.cache.create_cache``.
+
 ``django.utils.dictconfig``/``django.utils.importlib``
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 

docs/topics/cache.txt

@@ -703,7 +703,22 @@ pickling.)
 Accessing the cache
 -------------------
 
-.. function:: django.core.cache.get_cache(backend, **kwargs)
+.. versionadded:: 1.7
+
+You can access the caches configured in ``settings.CACHES`` through the
+dict-like ``django.core.cache.caches`` object. Repeated requests for the same
+alias will return the same object.
+
+    >>> from django.core.cache import caches
+    >>> cache1 = caches['myalias']
+    >>> cache2 = caches['myalias']
+    >>> cache1 is cache2
+    True
+
+If the named key does not exist, ``InvalidCacheBackendError`` will be raised.
+
+The ``caches`` dict is thread aware, so a different instance of each alias will
+be returned for each thread.
 
 The cache module, ``django.core.cache``, has a ``cache`` object that's
 automatically created from the ``'default'`` entry in the :setting:`CACHES`
@@ -711,13 +726,43 @@ setting::
 
     >>> from django.core.cache import cache
 
-If you have multiple caches defined in :setting:`CACHES`, then you can use
-:func:`django.core.cache.get_cache` to retrieve a cache object for any key::
+This is a proxy object to caches['default']. It is provided for backward
+compatiblity.
+
+.. function:: django.core.cache.create_cache(backend, **kwargs)
+
+You can create caches from ad-hoc configurations using ``create_cache``.
+
+    >>> from django.core.cache import create_cache
+    # Create an instance of a specific backend
+    >>> cache = create_cache(
+        'django.core.cache.backends.memcached.MemcachedCache',
+        LOCATION='/tmp/memcached.sock'
+    )
+    # Create a separate copy of the 'default' cache:
+    >>> new_default = create_cache('default')
+    # Create a cache with the same config as 'default', but a different timeout
+    >>> cache2 = create_cache('default', TIMEOUT=1)
+
+This is guaranteed to always create a new instance.
+
+.. function:: django.core.cache.get_cache(backend, **kwargs)
+
+.. deprecated:: 1.7
+    This function has been deprecated in favour of ``caches`` and
+    ``create_cache``.
+
+Before Django 1.7 this was the only way to get a cache instance.  Now it acts
+as a wrapper to ``create_cache``, except in the case where it is passed only a
+configured alias, where it will return the cache from ``caches``::
 
     >>> from django.core.cache import get_cache
-    >>> cache = get_cache('alternate')
-
-If the named key does not exist, ``InvalidCacheBackendError`` will be raised.
+    # Passes call to create_cache
+    >>> cache = get_cache('django.core.cache.backends.memcached.MemcachedCache', LOCATION='127.0.0.2')
+    # Creates a new cache based on the config in settings.CACHES['default']
+    >>> cache = get_cache('default', TIMEOUT=300)
+    # Returns instance from caches object
+    >>> cache = get_cache('default')
 
 
 Basic usage

tests/cache/tests.py

@@ -10,13 +10,14 @@ import random
 import re
 import string
 import tempfile
+import threading
 import time
 import unittest
 import warnings
 
 from django.conf import settings
 from django.core import management
-from django.core.cache import get_cache
+from django.core.cache import create_cache, caches
 from django.core.cache.backends.base import (CacheKeyWarning,
     InvalidCacheBackendError)
 from django.db import connection, router, transaction
@@ -55,7 +56,7 @@ class DummyCacheTests(unittest.TestCase):
     backend_name = 'django.core.cache.backends.dummy.DummyCache'
 
     def setUp(self):
-        self.cache = get_cache(self.backend_name)
+        self.cache = create_cache(self.backend_name)
 
     def test_simple(self):
         "Dummy cache backend ignores cache set calls"
@@ -840,11 +841,11 @@ class DBCacheTests(BaseCacheTests, TransactionTestCase):
         # Spaces are used in the table name to ensure quoting/escaping is working
         self._table_name = 'test cache table'
         management.call_command('createcachetable', verbosity=0, interactive=False)
-        self.cache = get_cache(self.backend_name, LOCATION=self._table_name, OPTIONS={'MAX_ENTRIES': 30})
-        self.prefix_cache = get_cache(self.backend_name, LOCATION=self._table_name, KEY_PREFIX='cacheprefix')
-        self.v2_cache = get_cache(self.backend_name, LOCATION=self._table_name, VERSION=2)
-        self.custom_key_cache = get_cache(self.backend_name, LOCATION=self._table_name, KEY_FUNCTION=custom_key_func)
-        self.custom_key_cache2 = get_cache(self.backend_name, LOCATION=self._table_name, KEY_FUNCTION='cache.tests.custom_key_func')
+        self.cache = create_cache(self.backend_name, LOCATION=self._table_name, OPTIONS={'MAX_ENTRIES': 30})
+        self.prefix_cache = create_cache(self.backend_name, LOCATION=self._table_name, KEY_PREFIX='cacheprefix')
+        self.v2_cache = create_cache(self.backend_name, LOCATION=self._table_name, VERSION=2)
+        self.custom_key_cache = create_cache(self.backend_name, LOCATION=self._table_name, KEY_FUNCTION=custom_key_func)
+        self.custom_key_cache2 = create_cache(self.backend_name, LOCATION=self._table_name, KEY_FUNCTION='cache.tests.custom_key_func')
 
     def tearDown(self):
         cursor = connection.cursor()
@@ -855,7 +856,7 @@ class DBCacheTests(BaseCacheTests, TransactionTestCase):
         self.perform_cull_test(50, 29)
 
     def test_zero_cull(self):
-        self.cache = get_cache(self.backend_name, LOCATION=self._table_name, OPTIONS={'MAX_ENTRIES': 30, 'CULL_FREQUENCY': 0})
+        self.cache = create_cache(self.backend_name, LOCATION=self._table_name, OPTIONS={'MAX_ENTRIES': 30, 'CULL_FREQUENCY': 0})
         self.perform_cull_test(50, 18)
 
     def test_second_call_doesnt_crash(self):
@@ -950,11 +951,11 @@ class LocMemCacheTests(unittest.TestCase, BaseCacheTests):
 
     def setUp(self):
         self.factory = RequestFactory()
-        self.cache = get_cache(self.backend_name, OPTIONS={'MAX_ENTRIES': 30})
-        self.prefix_cache = get_cache(self.backend_name, KEY_PREFIX='cacheprefix')
-        self.v2_cache = get_cache(self.backend_name, VERSION=2)
-        self.custom_key_cache = get_cache(self.backend_name, OPTIONS={'MAX_ENTRIES': 30}, KEY_FUNCTION=custom_key_func)
-        self.custom_key_cache2 = get_cache(self.backend_name, OPTIONS={'MAX_ENTRIES': 30}, KEY_FUNCTION='cache.tests.custom_key_func')
+        self.cache = create_cache(self.backend_name, OPTIONS={'MAX_ENTRIES': 30})
+        self.prefix_cache = create_cache(self.backend_name, KEY_PREFIX='cacheprefix')
+        self.v2_cache = create_cache(self.backend_name, VERSION=2)
+        self.custom_key_cache = create_cache(self.backend_name, OPTIONS={'MAX_ENTRIES': 30}, KEY_FUNCTION=custom_key_func)
+        self.custom_key_cache2 = create_cache(self.backend_name, OPTIONS={'MAX_ENTRIES': 30}, KEY_FUNCTION='cache.tests.custom_key_func')
 
         # LocMem requires a hack to make the other caches
         # share a data store with the 'normal' cache.
@@ -977,13 +978,13 @@ class LocMemCacheTests(unittest.TestCase, BaseCacheTests):
         self.perform_cull_test(50, 29)
 
     def test_zero_cull(self):
-        self.cache = get_cache(self.backend_name, OPTIONS={'MAX_ENTRIES': 30, 'CULL_FREQUENCY': 0})
+        self.cache = create_cache(self.backend_name, OPTIONS={'MAX_ENTRIES': 30, 'CULL_FREQUENCY': 0})
         self.perform_cull_test(50, 19)
 
     def test_multiple_caches(self):
         "Check that multiple locmem caches are isolated"
-        mirror_cache = get_cache(self.backend_name)
-        other_cache = get_cache(self.backend_name, LOCATION='other')
+        mirror_cache = create_cache(self.backend_name)
+        other_cache = create_cache(self.backend_name, LOCATION='other')
 
         self.cache.set('value1', 42)
         self.assertEqual(mirror_cache.get('value1'), 42)
@@ -1017,11 +1018,11 @@ class MemcachedCacheTests(unittest.TestCase, BaseCacheTests):
             if cache['BACKEND'].startswith('django.core.cache.backends.memcached.'):
                 break
         random_prefix = ''.join(random.choice(string.ascii_letters) for x in range(10))
-        self.cache = get_cache(cache_key)
-        self.prefix_cache = get_cache(cache_key, KEY_PREFIX=random_prefix)
-        self.v2_cache = get_cache(cache_key, VERSION=2)
-        self.custom_key_cache = get_cache(cache_key, KEY_FUNCTION=custom_key_func)
-        self.custom_key_cache2 = get_cache(cache_key, KEY_FUNCTION='cache.tests.custom_key_func')
+        self.cache = caches[cache_key]
+        self.prefix_cache = create_cache(cache_key, KEY_PREFIX=random_prefix)
+        self.v2_cache = create_cache(cache_key, VERSION=2)
+        self.custom_key_cache = create_cache(cache_key, KEY_FUNCTION=custom_key_func)
+        self.custom_key_cache2 = create_cache(cache_key, KEY_FUNCTION='cache.tests.custom_key_func')
 
     def tearDown(self):
         self.cache.clear()
@@ -1050,7 +1051,7 @@ class MemcachedCacheTests(unittest.TestCase, BaseCacheTests):
         # Regression test for #19810
         for cache_key, cache in settings.CACHES.items():
             if cache['BACKEND'] == 'django.core.cache.backends.memcached.MemcachedCache':
-                self.assertEqual(get_cache(cache_key)._cache.pickleProtocol,
+                self.assertEqual(caches[cache_key]._cache.pickleProtocol,
                                  pickle.HIGHEST_PROTOCOL)
 
 
@@ -1063,11 +1064,11 @@ class FileBasedCacheTests(unittest.TestCase, BaseCacheTests):
     def setUp(self):
         self.factory = RequestFactory()
         self.dirname = tempfile.mkdtemp()
-        self.cache = get_cache(self.backend_name, LOCATION=self.dirname, OPTIONS={'MAX_ENTRIES': 30})
-        self.prefix_cache = get_cache(self.backend_name, LOCATION=self.dirname, KEY_PREFIX='cacheprefix')
-        self.v2_cache = get_cache(self.backend_name, LOCATION=self.dirname, VERSION=2)
-        self.custom_key_cache = get_cache(self.backend_name, LOCATION=self.dirname, KEY_FUNCTION=custom_key_func)
-        self.custom_key_cache2 = get_cache(self.backend_name, LOCATION=self.dirname, KEY_FUNCTION='cache.tests.custom_key_func')
+        self.cache = create_cache(self.backend_name, LOCATION=self.dirname, OPTIONS={'MAX_ENTRIES': 30})
+        self.prefix_cache = create_cache(self.backend_name, LOCATION=self.dirname, KEY_PREFIX='cacheprefix')
+        self.v2_cache = create_cache(self.backend_name, LOCATION=self.dirname, VERSION=2)
+        self.custom_key_cache = create_cache(self.backend_name, LOCATION=self.dirname, KEY_FUNCTION=custom_key_func)
+        self.custom_key_cache2 = create_cache(self.backend_name, LOCATION=self.dirname, KEY_FUNCTION='cache.tests.custom_key_func')
 
     def tearDown(self):
         self.cache.clear()
@@ -1097,7 +1098,7 @@ class FileBasedCacheTests(unittest.TestCase, BaseCacheTests):
 
     def test_zero_cull(self):
         # Regression test for #15806
-        self.cache = get_cache(self.backend_name, LOCATION=self.dirname, OPTIONS={'MAX_ENTRIES': 30, 'CULL_FREQUENCY': 0})
+        self.cache = create_cache(self.backend_name, LOCATION=self.dirname, OPTIONS={'MAX_ENTRIES': 30, 'CULL_FREQUENCY': 0})
         self.perform_cull_test(50, 19)
 
 
@@ -1109,7 +1110,7 @@ class CustomCacheKeyValidationTests(unittest.TestCase):
 
     """
     def test_custom_key_validation(self):
-        cache = get_cache('cache.liberal_backend.CacheClass')
+        cache = create_cache('cache.liberal_backend.CacheClass')
 
         # this key is both longer than 250 characters, and has spaces
         key = 'some key with spaces' * 15
@@ -1121,18 +1122,23 @@ class CustomCacheKeyValidationTests(unittest.TestCase):
 class GetCacheTests(unittest.TestCase):
 
     def test_simple(self):
-        from django.core.cache import cache
-        self.assertIsInstance(cache, get_cache('default').__class__)
+        from django.core.cache import caches, DEFAULT_CACHE_ALIAS
+        self.assertIsInstance(
+            caches[DEFAULT_CACHE_ALIAS],
+            create_cache('default').__class__
+        )
 
-        cache = get_cache(
-            'django.core.cache.backends.dummy.DummyCache', **{'TIMEOUT': 120})
+        cache = create_cache(
+            'django.core.cache.backends.dummy.DummyCache',
+            **{'TIMEOUT': 120}
+        )
         self.assertEqual(cache.default_timeout, 120)
 
-        self.assertRaises(InvalidCacheBackendError, get_cache, 'does_not_exist')
+        self.assertRaises(InvalidCacheBackendError, create_cache, 'does_not_exist')
 
     def test_close(self):
         from django.core import signals
-        cache = get_cache('cache.closeable_cache.CacheClass')
+        cache = create_cache('cache.closeable_cache.CacheClass')
         self.assertFalse(cache.closed)
         signals.request_finished.send(self.__class__)
         self.assertTrue(cache.closed)
@@ -1153,7 +1159,7 @@ class CacheUtils(TestCase):
 
     def setUp(self):
         self.path = '/cache/test/'
-        self.cache = get_cache('default')
+        self.cache = caches['default']
         self.factory = RequestFactory()
 
     def tearDown(self):
@@ -1261,7 +1267,7 @@ class CacheHEADTest(TestCase):
 
     def setUp(self):
         self.path = '/cache/test/'
-        self.cache = get_cache('default')
+        self.cache = caches['default']
         self.factory = RequestFactory()
 
     def tearDown(self):
@@ -1314,7 +1320,7 @@ class CacheI18nTest(TestCase):
 
     def setUp(self):
         self.path = '/cache/test/'
-        self.cache = get_cache('default')
+        self.cache = create_cache('default')
         self.factory = RequestFactory()
 
     def tearDown(self):
@@ -1581,8 +1587,8 @@ class CacheMiddlewareTest(IgnoreDeprecationWarningsMixin, TestCase):
     def setUp(self):
         super(CacheMiddlewareTest, self).setUp()
         self.factory = RequestFactory()
-        self.default_cache = get_cache('default')
-        self.other_cache = get_cache('other')
+        self.default_cache = create_cache('default')
+        self.other_cache = create_cache('other')
 
     def tearDown(self):
         self.default_cache.clear()
@@ -1608,7 +1614,7 @@ class CacheMiddlewareTest(IgnoreDeprecationWarningsMixin, TestCase):
         # First, test with "defaults":
         as_view_decorator = CacheMiddleware(cache_alias=None, key_prefix=None)
 
-        self.assertEqual(as_view_decorator.cache_timeout, 300)  # Timeout value for 'default' cache, i.e. 300
+        self.assertEqual(as_view_decorator.cache_timeout, 30)  # Timeout value for 'default' cache, i.e. 30
         self.assertEqual(as_view_decorator.key_prefix, '')
         self.assertEqual(as_view_decorator.cache_alias, 'default')  # Value of DEFAULT_CACHE_ALIAS from django.core.cache
         self.assertEqual(as_view_decorator.cache_anonymous_only, False)
@@ -1755,7 +1761,7 @@ class CacheMiddlewareTest(IgnoreDeprecationWarningsMixin, TestCase):
         time.sleep(2)
 
         # ... the default cache will still hit
-        get_cache('default')
+        caches['default']
         response = default_view(request, '11')
         self.assertEqual(response.content, b'Hello World 1')
 
@@ -1801,7 +1807,7 @@ class TestWithTemplateResponse(TestCase):
     """
     def setUp(self):
         self.path = '/cache/test/'
-        self.cache = get_cache('default')
+        self.cache = create_cache('default')
         self.factory = RequestFactory()
 
     def tearDown(self):
@@ -1904,3 +1910,29 @@ class TestMakeTemplateFragmentKey(TestCase):
         key = make_template_fragment_key('spam', ['abc:def%'])
         self.assertEqual(key,
             'template.cache.spam.f27688177baec990cdf3fbd9d9c3f469')
+
+class CacheHandlerTest(TestCase):
+    def test_same_instance(self):
+        """
+        Attempting to retrieve the same alias should yield the same instance.
+        """
+        cache1 = caches['default']
+        cache2 = caches['default']
+
+        self.assertTrue(cache1 is cache2)
+
+    def test_per_thread(self):
+        """
+        Requesting the same alias from separate threads should yield separate
+        instances.
+        """
+        c = []
+        def runner():
+            c.append(caches['default'])
+
+        for x in range(2):
+            t = threading.Thread(target=runner)
+            t.start()
+            t.join()
+
+        self.assertFalse(c[0] is c[1])