Merge branch '4.4' into 5.1

OskarStark · OskarStark · commit b8eaae0ece11 · 2020-12-16T14:44:05.000+01:00
* 4.4: minor. refs symfony#14683 Add documentation about redis cache configuration
diff --git a/components/cache/adapters/redis_adapter.rst b/components/cache/adapters/redis_adapter.rst
@@ -193,6 +193,23 @@ In order to use tag-based invalidation, you can wrap your adapter in :class:`Sym
     $client = RedisAdapter::createConnection('redis://localhost');
     $cache = new RedisTagAwareAdapter($client);
 
+Configuring Redis
+~~~~~~~~~~~~~~~~~
+
+When using Redis as cache, you should configure the ``maxmemory`` and ``maxmemory-policy``
+settings. By setting ``maxmemory``, you limit how much memory Redis is allowed to consume.
+If the amount is too low, Redis will drop entries that would still be useful and you benefit
+less from your cache. Setting the ``maxmemory-policy`` to ``allkeys-lru`` tells Redis that
+it is ok to drop data when it runs out of memory, and to first drop the oldest entries (least
+recently used). If you do not allow Redis to drop entries, it will return an error when you
+try to add data when no memory is available. An example setting could look as follows:
+
+.. code-block:: ini
+
+    maxmemory 100mb
+    maxmemory-policy allkeys-lru
+
+Read more about this topic in the offical `Redis LRU Cache Documentation`_.
 
 .. _`Data Source Name (DSN)`: https://en.wikipedia.org/wiki/Data_source_name
 .. _`Redis server`: https://redis.io/
@@ -203,3 +220,4 @@ In order to use tag-based invalidation, you can wrap your adapter in :class:`Sym
 .. _`Predis Connection Parameters`: https://github.com/nrk/predis/wiki/Connection-Parameters#list-of-connection-parameters
 .. _`TCP-keepalive`: https://redis.io/topics/clients#tcp-keepalive
 .. _`Redis Sentinel`: https://redis.io/topics/sentinel
+.. _`Redis LRU Cache Documentation`: https://redis.io/topics/lru-cache
