Add configurable Synapse room complexity limit variables

docs/faq.md

@@ -323,11 +323,9 @@ matrix_synapse_presence_enabled: false
 You can also consider implementing a restriction on room complexity, in order to prevent users from joining very heavy rooms:
 
 ```yaml
-matrix_synapse_configuration_extension_yaml: |
-  limit_remote_rooms:
-    enabled: true
-    complexity: 1.0 # this limits joining complex (~large) rooms, can be
-					# increased, but larger values can require more RAM
+matrix_synapse_limit_remote_rooms_enabled: true
+matrix_synapse_limit_remote_rooms_complexity: 1.0 # this limits joining complex (~large) rooms
+# can be increased, but larger values can require more RAM
 ```
 
 If you've installed [Jitsi](configuring-playbook-jitsi.md) (not installed by default), there are additional optimizations listed on its documentation page that you can perform.

roles/custom/matrix-synapse/defaults/main.yml

@@ -570,6 +570,21 @@ matrix_synapse_report_stats_endpoint: "https://matrix.org/report-usage-stats/pus
 # disabling this will decrease server load significantly.
 matrix_synapse_presence_enabled: true
 
+# Controls whether remote room complexity checks are enabled when joining rooms.
+# When enabled, Synapse checks a room's complexity before joining a remote room.
+# Complexity is measured as `current_state_events / 500` and can prevent
+# users from joining very large/active rooms on constrained servers.
+matrix_synapse_limit_remote_rooms_enabled: false
+
+# Maximum complexity allowed before join is blocked.
+matrix_synapse_limit_remote_rooms_complexity: 1.0
+
+# Error message returned when a user attempts to join a too-complex room.
+matrix_synapse_limit_remote_rooms_complexity_error: "Your homeserver is unable to join rooms this large or complex. Please speak to your server administrator, or upgrade your instance to join this room."
+
+# Allow server admins to join rooms even when they exceed the complexity limit.
+matrix_synapse_limit_remote_rooms_admins_can_join: false
+
 # Controls whether accessing the server's public rooms directory can be done without authentication.
 # For private servers, you most likely wish to require authentication,
 # unless you know what list of rooms you're publishing to the world and explicitly want to do it.

roles/custom/matrix-synapse/templates/synapse/homeserver.yaml.j2

@@ -452,30 +452,11 @@ admin_contact: {{ matrix_synapse_admin_contact | to_json }}
 #server_context: context
 
 # Resource-constrained homeserver settings
-#
-# When this is enabled, the room "complexity" will be checked before a user
-# joins a new remote room. If it is above the complexity limit, the server will
-# disallow joining, or will instantly leave.
-#
-# Room complexity is an arbitrary measure based on factors such as the number of
-# users in the room.
-#
 limit_remote_rooms:
-  # Uncomment to enable room complexity checking.
-  #
-  #enabled: true
-
-  # the limit above which rooms cannot be joined. The default is 1.0.
-  #
-  #complexity: 0.5
-
-  # override the error which is returned when the room is too complex.
-  #
-  #complexity_error: "This room is too complex."
-
-  # allow server admins to join complex rooms. Default is false.
-  #
-  #admins_can_join: true
+  enabled: {{ matrix_synapse_limit_remote_rooms_enabled | to_json }}
+  complexity: {{ matrix_synapse_limit_remote_rooms_complexity | to_json }}
+  complexity_error: {{ matrix_synapse_limit_remote_rooms_complexity_error | to_json }}
+  admins_can_join: {{ matrix_synapse_limit_remote_rooms_admins_can_join | to_json }}
 
 # Whether to require a user to be in the room to add an alias to it.
 # Defaults to 'true'.