From 7c33cc7f5ef4597b55dde561c1752db4d0feaca1 Mon Sep 17 00:00:00 2001
From: Malcolm Tredinnick <malcolm.tredinnick@gmail.com>
Date: Fri, 25 Jul 2008 18:51:32 +0000
Subject: [PATCH] Fixed #7398 -- Allow for custom cache-backends to be used.

Based on a patch from Lau Bech Lauritzen and Brenton Simpson.


git-svn-id: http://code.djangoproject.com/svn/django/trunk@8075 bcc190cf-cafb-0310-a4f2-bffc1f526a37
---
 AUTHORS                       |  2 ++
 django/core/cache/__init__.py | 13 ++++++++-----
 docs/cache.txt                | 25 +++++++++++++++++++++++--
 3 files changed, 33 insertions(+), 7 deletions(-)

diff --git a/AUTHORS b/AUTHORS
index e22ee45cbf..8e05c927d8 100644
--- a/AUTHORS
+++ b/AUTHORS
@@ -236,6 +236,7 @@ answer newbie questions, and generally made Django that much better:
     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
@@ -341,6 +342,7 @@ answer newbie questions, and generally made Django that much better:
     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>
     sloonz <simon.lipp@insa-lyon.fr>
diff --git a/django/core/cache/__init__.py b/django/core/cache/__init__.py
index 495cc92822..27f7a3b06c 100644
--- a/django/core/cache/__init__.py
+++ b/django/core/cache/__init__.py
@@ -19,8 +19,10 @@ from cgi import parse_qsl
 from django.conf import settings
 from django.core.cache.backends.base import InvalidCacheBackendError
 
+# Name for use in settings file --> name of module in "backends" directory.
+# Any backend scheme that is not in this dictionary is treated as a Python
+# import path to a custom backend.
 BACKENDS = {
-    # name for use in settings file --> name of module in "backends" directory
     'memcached': 'memcached',
     'locmem': 'locmem',
     'file': 'filebased',
@@ -44,8 +46,6 @@ def get_cache(backend_uri):
         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('?')
@@ -57,7 +57,10 @@ def get_cache(backend_uri):
     if host.endswith('/'):
         host = host[:-1]
 
-    cache_class = getattr(__import__('django.core.cache.backends.%s' % BACKENDS[scheme], {}, {}, ['']), 'CacheClass')
-    return cache_class(host, params)
+    if scheme in BACKENDS:
+        module = __import__('django.core.cache.backends.%s' % BACKENDS[scheme], {}, {}, [''])
+    else:
+        module = __import__(scheme, {}, {}, [''])
+    return getattr(module, 'CacheClass')(host, params)
 
 cache = get_cache(settings.CACHE_BACKEND)
diff --git a/docs/cache.txt b/docs/cache.txt
index 3318b2ad4a..392fef8f5b 100644
--- a/docs/cache.txt
+++ b/docs/cache.txt
@@ -6,8 +6,8 @@ A fundamental tradeoff in dynamic Web sites is, well, they're dynamic. Each
 time a user requests a page, the Web server makes all sorts of calculations --
 from database queries to template rendering to business logic -- to create the
 page that your site's visitor sees. This is a lot more expensive, from a
-processing-overhead perspective, than your standard read-a-file-off-the-filesystem
-server arrangement.
+processing-overhead perspective, than your standard
+read-a-file-off-the-filesystem server arrangement.
 
 For most Web applications, this overhead isn't a big deal. Most Web
 applications aren't washingtonpost.com or slashdot.org; they're simply small-
@@ -186,6 +186,27 @@ production environment still will. To activate dummy caching, set
 
     CACHE_BACKEND = 'dummy:///'
 
+Using a custom cache backend
+----------------------------
+
+**New in Django development version**
+
+While Django includes support for a number of cache backends out-of-the-box,
+sometimes you will want to use a customised verison or your own backend.  To
+use an external cache backend with Django, use a Python import path as the
+scheme portion (the part before the initial colon) of the ``CACHE_BACKEND``
+URI, like so::
+
+    CACHE_BACKEND = 'path.to.backend://'
+
+If you're building your own backend, you can use the standard cache backends
+as reference implementations. You'll find the code in the
+``django/core/cache/backends/`` directory of the Django source.
+
+Note: Without a really compelling reason, like a host that doesn't support the
+them, you should stick to the cache backends included with Django. They've
+been really well-tested and are quite easy to use.
+
 CACHE_BACKEND arguments
 -----------------------