The cache storage storage_inmemory is now the default

Documentation/Filters/Cache.md

@@ -71,8 +71,6 @@ type=filter
 module=cache
 hard_ttl=30
 soft_ttl=20
-storage=...
-storage_options=...
 rules=...
 ...
 
@@ -95,10 +93,10 @@ sharing.
 
 ### Filter Parameters
 
-The cache filter has one mandatory parameter - `storage` - and a few
-optional ones. Note that it is advisable to specify `max_size` to prevent
-the cache from using up all memory there is, in case there is very litte
-overlap among the queries.
+The cache filter has no mandatory parameters but a range of optional ones.
+Note that it is advisable to specify `max_size` to prevent the cache from
+using up all memory there is, in case there is very litte overlap among the
+queries.
 
 #### `storage`
 
@@ -108,6 +106,8 @@ argument. For instance:
 ```
 storage=storage_inmemory
 ```
+The default is `storage_inmemory`.
+
 See [Storage](#storage-1) for what storage modules are available.
 
 #### `storage_options`

Documentation/Release-Notes/MaxScale-2.1.2-Release-Notes.md

@@ -15,6 +15,11 @@ report at [Jira](https://jira.mariadb.org).
 
 ## Changed Features
 
+### Cache
+
+* The storage `storage_inmemory` is now the default, so the parameter
+  `storage` no longer need to be set explicitly.
+
 ### Improved Wildcard Matching
 
 The MySQLAuth module now supports all types of wildcards for both IP addresses

server/modules/filter/cache/cachefilter.cc

@@ -153,8 +153,7 @@ extern "C" MXS_MODULE* MXS_CREATE_MODULE()
             {
                 "storage",
                 MXS_MODULE_PARAM_STRING,
-                NULL,
-                MXS_MODULE_OPT_REQUIRED
+                CACHE_DEFAULT_STORAGE
             },
             {
                 "storage_options",

server/modules/filter/cache/cachefilter.h

@@ -56,6 +56,8 @@
 #define CACHE_DEFAULT_THREAD_MODEL       "shared"
 // Cacheable selects
 #define CACHE_DEFAULT_SELECTS            "verify_cacheable"
+// Storage
+#define CACHE_DEFAULT_STORAGE            "storage_inmemory"
 
 typedef enum cache_selects
 {