Document "enforce_simple_topology"-setting

Documentation/Changelog.md

@@ -17,7 +17,8 @@
   by adding the `--rdns`-option to the command.
 * 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.
+  setting `detect_replication_lag` is deprecated and ignored.
+* `enforce_simple_topology`-setting added to MariaDB-Monitor.
 * The mqfilter has been deprecated.
 
 For more details, please refer to:

Documentation/Monitors/MariaDB-Monitor.md

@@ -30,6 +30,7 @@ Table of Contents
         * [auto_failover](#auto_failover)
         * [auto_rejoin](#auto_rejoin)
         * [switchover_on_low_disk_space](#switchover_on_low_disk_space)
+        * [enforce_simple_topology](#enforce_simple_topology)
         * [replication_user and replication_password](#replication_user-and-replication_password)
         * [failover_timeout and switchover_timeout](#failover_timeout-and-switchover_timeout)
         * [verify_master_failure and master_failure_timeout](#verify_master_failure-and-master_failure_timeout)
@@ -644,6 +645,23 @@ must be defined for the monitor.
 switchover_on_low_disk_space=true
 ```
 
+#### `enforce_simple_topology`
+
+This setting tells the monitor to assume that the servers should be arranged in a
+1-master-N-slaves topology and the monitor should try to keep it that way. If
+`enforce_simple_topology` is enabled, the settings `assume_unique_hostnames`,
+`auto_failover` and `auto_rejoin` are also activated regardless of their individual
+settings.
+
+This setting also allows the monitor to perform a failover to a cluster where the master
+server has not been seen [Running]. This is usually the case when the master goes down
+before MaxScale is started. When using this feature, the monitor will guess the GTID
+domain id of the master from the slaves. For reliable results, the GTID:s of the cluster
+should be simple.
+```
+enforce_simple_topology=true
+```
+
 #### `replication_user` and `replication_password`
 
 The username and password of the replication user. These are given as the values

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

@@ -75,6 +75,11 @@ The `ndbclustermon` module has been removed.
 The `mmmon` module has been removed as the `mariadbmon` monitor largely does
 what it used to do.
 
+### MariaDB-Monitor settings
+
+The following settings have been removed and cause a startup error
+if defined: `mysql51_replication`, `multimaster` and `allow_cluster_recovery`.
+
 ### `log_to_shm`
 
 The `log_to_shm` parameter that was removed in 2.3 will be treated as an unknown
@@ -302,6 +307,13 @@ is done directly from a remote master server. This skips the binlogrouter
 definition completely making the conversion process faster and more space
 efficient.
 
+### `enforce_simple_topology`
+
+This MariaDB-Monitor setting allows the monitor greater freedom in managing the
+backend servers. Please see
+[MariaDB-Monitor documentation](../Monitors/MariaDB-Monitor.md#enforce_simple_topology)
+for more information.
+
 ## Bug fixes
 
 [Here is a list of bugs fixed in MaxScale 2.4.0.](https://jira.mariadb.org/issues/?jql=project%20%3D%20MXS%20AND%20issuetype%20%3D%20Bug%20AND%20status%20%3D%20Closed%20AND%20fixVersion%20%3D%202.4.0)