document server groups

2 files changed, 23 insertions, 0 deletions

diff --git a/doc/config.md b/doc/config.md
index e1eed63..f517623 100644
--- a/doc/config.md
+++ b/doc/config.md
@@ -136,6 +136,8 @@ selection accept server groups on top of regular server names,
 randomly choosing one of its servers. If a server name and a group name
 are in conflict, the server name is preferred.
 This feature can be used to implement simple load balancing.
+See [server_groups.md](https://github.com/HimbeerserverDE/mt-multiserver-proxy/blob/main/doc/server_groups.md)
+for more information.
 ```
 
 > `Server.Fallbacks`
diff --git a/doc/server_groups.md b/doc/server_groups.md
new file mode 100644
index 0000000..4a0140a
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+++ b/doc/server_groups.md
@@ -0,0 +1,21 @@
+# Server groups
+
+Servers can be made members of multiple server groups by listing them
+in the `Groups` subfield of the server definition in the config.
+Configuration options that support server groups will randomly choose
+from their member servers every time they are applied to a client.
+
+Neither local nor global fallback servers can be server groups.
+
+If there is a server group with the same name as a regular server,
+the regular server is preferred, rendering the group inaccessible.
+
+## Use cases
+
+Server groups provide a simple builtin load balancing solution.
+The default server may be a server group, distributing the load
+over multiple Minetest lobby servers.
+
+Server groups are also available to plugins, making it possible to use them
+for custom features such as requiring special permissions to access a certain
+server group.