Deprecate mqfilter

Documentation/Changelog.md

@@ -18,6 +18,7 @@
 * The following MariaDB-Monitor settings have been removed and cause a startup error
   if defined: `mysql51_replication`, `multimaster` and `allow_cluster_recovery`. The
   setting `detect_replication_lag` is deprecated and is ignored.
+* The mqfilter has been deprecated.
 
 For more details, please refer to:
 

Documentation/Filters/RabbitMQ-Filter.md

@@ -2,6 +2,9 @@
 
 ## Overview
 
+The **mqfilter** has been deprecated in MaxScale 2.4 and it will be removed
+in a future version of MaxScale. We advise against using it.
+
 This filter is designed to extract queries and transform them into a canonical
 form e.g. `INSERT INTO database.table VALUES ("John Doe", "Downtown",100,50.0);`
 turns into `INSERT INTO database.table VALUES ("?", "?",?,?);`. The filter

Documentation/Release-Notes/MaxScale-2.4.0-Release-Notes.md

@@ -80,6 +80,15 @@ what it used to do.
 The `log_to_shm` parameter that was removed in 2.3 will be treated as an unknown
 parameter in 2.4.0.
 
+## Deprecated Features
+
+### `mqfilter`
+
+The `mqfilter` has been deprecated and it will be removed in a future version
+of MaxScale.
+
+We advise against using it.
+
 ## New Features
 
 ### Clustrix Support

server/modules/filter/mqfilter/mqfilter.cc

@@ -570,6 +570,9 @@ char** parse_optstr(const char* str, const char* tok, int* szstore)
  */
 static MXS_FILTER* createInstance(const char* name, MXS_CONFIG_PARAMETER* params)
 {
+    MXS_WARNING("The mqfilter has been DEPRECATED in MaxScale 2.4 "
+                "and it will be removed in a future release of MaxScale.");
+
     MQ_INSTANCE* my_instance = static_cast<MQ_INSTANCE*>(MXS_CALLOC(1, sizeof(MQ_INSTANCE)));
 
     if (my_instance)