Add RedisCacheBackend

docs/cache-backends.rst

@@ -16,3 +16,7 @@ directly in ``get_thumbnail`` if the cache returns it.
 .. autoclass:: thumbnails.cache_backends.DjangoCacheBackend
     :members:
     :private-members:
+
+.. autoclass:: thumbnails.cache_backends.RedisCacheBackend
+    :members:
+    :private-members:

tests/test_cache_backends.py

@@ -1,15 +1,15 @@
 # -*- coding: utf-8 -*-
 import unittest
 
-from thumbnails.cache_backends import BaseCacheBackend, DjangoCacheBackend, SimpleCacheBackend
+from thumbnails.cache_backends import (BaseCacheBackend, DjangoCacheBackend, RedisCacheBackend,
+                                       SimpleCacheBackend)
 from thumbnails.images import Thumbnail
 
 from .compat import mock
-from .utils import has_django
+from .utils import has_django, has_redis
 
 
 class CacheBackendTestMixin(object):
-
     def setUp(self):
         self.backend = self.BACKEND()
 
@@ -25,7 +25,6 @@ def test_set_and_get(self):
 
 
 class BaseCacheBackendTestCase(unittest.TestCase):
-
     def setUp(self):
         self.backend = BaseCacheBackend()
 
@@ -52,3 +51,20 @@ class SimpleCacheBackendTestCase(CacheBackendTestMixin, unittest.TestCase):
 @unittest.skipIf(not has_django(), 'Django is not installed')
 class DjangoCacheBackendTestCase(CacheBackendTestMixin, unittest.TestCase):
     BACKEND = DjangoCacheBackend
+
+
+@unittest.skipIf(not has_redis(), 'Redis not installed')
+class RedisCacheBackendTestCase(CacheBackendTestMixin, unittest.TestCase):
+    BACKEND = RedisCacheBackend
+
+    def test_get_settings(self):
+        settings = self.backend.get_settings()
+        self.assertEqual(settings['host'], '127.0.0.1')
+        self.assertEqual(settings['port'], 6379)
+        self.assertEqual(settings['db'], 0)
+
+        self.backend.connection_uri = 'redis://example.com:1234/9'
+        settings = self.backend.get_settings()
+        self.assertEqual(settings['host'], 'example.com')
+        self.assertEqual(settings['port'], 1234)
+        self.assertEqual(settings['db'], 9)

tests/utils.py

@@ -1,17 +1,22 @@
 # -*- coding: utf-8 -*-
+import importlib
 
 
-def has_django():
+def has_installed(dependency):
     try:
-        import django  # noqa isort:skip
+        importlib.import_module(dependency)
         return True
     except ImportError:
         return False
 
 
+def has_django():
+    return has_installed('django')
+
+
 def has_pillow():
-    try:
-        from PIL import Image  # noqa isort:skip
-        return True
-    except ImportError:
-        return False
+    return has_installed('PIL.Image')
+
+
+def has_redis():
+    return has_installed('redis')

thumbnails/cache_backends.py

@@ -1,4 +1,7 @@
 # -*- coding: utf-8 -*-
+import pickle
+import re
+
 from thumbnails import settings
 
 
@@ -77,3 +80,59 @@ def _get(self, thumbnail_name):
 
     def _set(self, thumbnail_name, thumbnail):
         self.cache.set(thumbnail_name.replace('/', ''), thumbnail, timeout=self.TIMEOUT)
+
+
+class RedisCacheBackend(BaseCacheBackend):
+    """
+    Cache backend that connects to Redis with redis-py. It uses the
+    ``THUMBNAIL_CACHE_CONNECTION_URI`` setting as connection configuration.
+    The setting should contain a string on the form: ``redis://host:port/db``,
+    example: ``redis://127.0.0.1:6379/0`` will give the default settings.
+    This backend does not sett time-to-live on the cached items, thus they will
+    be in redis until they are deleted.
+
+    If the settings string is not good enough for your configuration, it is possible to extend
+    this backend and override ``get_settings``.
+    """
+
+    def __init__(self):
+        import redis
+        super(RedisCacheBackend, self).__init__()
+        self.connection_uri = getattr(settings, 'THUMBNAIL_CACHE_CONNECTION_URI', None)
+        self.redis = redis.StrictRedis(**self.get_settings())
+
+    def _get(self, thumbnail_name):
+        thumbnail = self.redis.get(thumbnail_name)
+        if thumbnail is not None:
+            return pickle.loads(thumbnail)
+
+    def _set(self, thumbnail_name, thumbnail):
+        return self.redis.set(thumbnail_name, pickle.dumps(thumbnail))
+
+    def get_settings(self):
+        """
+        This creates a dict with keyword arguments used to create the redis client.
+        It is used like ``redis.StrictClient(**self.get_settings())``. Thus, if the
+        settings string is not enough to generate the wanted setting you can override
+        this function.
+
+        :return: A dict with keyword arguments for the redis client constructor.
+        """
+        host = '127.0.0.1'
+        port = 6379
+        db = 0
+        if self.connection_uri is not None:
+            match = re.match(r'redis://(?:([\w]+)@)?([\w\d\.]+):(\d+)(?:/(\d+))?', self.connection_uri)
+            if match:
+                if match.group(2):
+                    host = match.group(2)
+                if match.group(3):
+                    port = int(match.group(3))
+                if match.group(4):
+                    db = int(match.group(4))
+
+        return {
+            'host': host,
+            'port': port,
+            'db': db
+        }

thumbnails/conf/defaults.py

@@ -6,6 +6,7 @@
 THUMBNAIL_ENGINE = 'thumbnails.engines.PillowEngine'
 THUMBNAIL_CACHE_BACKEND = 'thumbnails.cache_backends.SimpleCacheBackend'
 THUMBNAIL_CACHE_TIMEOUT = 60 * 60 * 24 * 365
+THUMBNAIL_CACHE_CONNECTION_URI = None
 THUMBNAIL_STORAGE_BACKEND = 'thumbnails.storage_backends.FilesystemStorageBackend'
 
 THUMBNAIL_SCALE_UP = False

tox.ini

@@ -1,7 +1,7 @@
 [tox]
 envlist =
     {py27,py34},
-    {py27,py34}-{django17,django18},
+    {py27,py34}-{django17,django18,redis},
     py34-docs
 skipsdist = True
 
@@ -31,6 +31,7 @@ deps =
     django16: Django>=1.6,<1.7
     django17: Django>=1.7,<1.8
     django18: Django==1.8c1
+    redis: redis
     docs: -r{toxinidir}/docs/requirements.txt
 
 [testenv:py34-docs]