Ticket #7398: importable-backends.diff

docs/cache.txt

@@ -182 +182 @@
 various places but a development/test environment on which you don't want to
 cache. As a result, your development environment won't use caching and your
 production environment still will. To activate dummy caching, set
-``CACHE_BACKEND`` like so::
+``CACHE_BACKEND`` like so:
 
     CACHE_BACKEND = 'dummy:///'
 
+Using your own cache backend
+----------------------------
+
+**New in Django development version**
+
+While Django includes support for many cache backends out-of-the-box, sometimes
+that just isn't enough.  Consider, for instance, Google App Engine.  Google
+will host your Django for you, but to maintain a safe and stable platform, it
+replaces a few common modules like memcached and PIL with its own variants.  
+Fear not; Django makes it easy to include third-party backends in case the 
+included ones just won't cut the mustard.  All you need to do is supply the 
+full Python path to the backend in the ``CACHE_BACKEND`` setting, like so:
+
+    CACHE_BACKEND = 'path.to.cache_backend:///'
+
+Make sure, of course, that ``path.to.cache_backend`` is a valid Django backend.  If
+you're building your own backend, you can use the baked-in cache backends as
+reference.  You'll find them at ``django.core.cache.backends``.
+
+Note: Without a really compelling reason, like a host that doesn't support the
+them, you should stick to the ones included with Django.  They've been really 
+well-tested and are quite easy to use.
+
 CACHE_BACKEND arguments
 -----------------------
 

AUTHORS

@@ -227 +227 @@
     Stuart Langridge <http://www.kryogenix.org/>
     Paul Lanier <planier@google.com>
     Nicola Larosa <nico@teknico.net>
+    Lau Bech Lauritzen
     Rune Rønde Laursen <runerl@skjoldhoej.dk>
     Eugene Lazutkin <http://lazutkin.com/blog/>
     lcordier@point45.com
@@ -323 +324 @@
     Pete Shinners <pete@shinners.org>
     Leo Shklovskii
     jason.sidabras@gmail.com
+    Brenton Simpson <http://theillustratedlife.com>
     Jozko Skrablin <jozko.skrablin@gmail.com>
     Ben Slavin <benjamin.slavin@gmail.com>
     SmileyChris <smileychris@gmail.com>

django/core/cache/__init__.py

@@ -21 +21 @@
 
 BACKENDS = {
     # name for use in settings file --> name of module in "backends" directory
-    'memcached': 'memcached',
-    'locmem': 'locmem',
-    'file': 'filebased',
-    'db': 'db',
-    'dummy': 'dummy',
+    'memcached': 'django.core.cache.backends.memcached',
+    'locmem': 'django.core.cache.backends.locmem',
+    'file': 'django.core.cache.backends.filebased',
+    'db': 'django.core.cache.backends.db',
+    'dummy': 'django.core.cache.backends.dummy',
 }
 
 DEPRECATED_BACKENDS = {
@@ -44 +44 @@
         warnings.warn("'%s' backend is deprecated. Use '%s' instead." % 
             (scheme, DEPRECATED_BACKENDS[scheme]), DeprecationWarning)
         scheme = DEPRECATED_BACKENDS[scheme]
-    if scheme not in BACKENDS:
-        raise InvalidCacheBackendError, "%r is not a valid cache backend" % scheme
 
     host = rest[2:]
     qpos = rest.find('?')
@@ -56 +54 @@
         params = {}
     if host.endswith('/'):
         host = host[:-1]
-
-    cache_class = getattr(__import__('django.core.cache.backends.%s' % BACKENDS[scheme], {}, {}, ['']), 'CacheClass')
+        
+    backend_path = scheme
+    if scheme in BACKENDS:
+        backend_path = BACKENDS[scheme]
+    try:
+        backend_import = __import__(backend_path, {}, {}, [''])
+    except ImportError:
+        raise InvalidCacheBackendError, "Cache backend "+backend_path+" cannot be found."        
+    
+    cache_class = getattr(backend_import, 'CacheClass')
     return cache_class(host, params)