Feature flags: Call the migration function after the flag is marked as enabled

This allows the migration function do perform some cleanup after the
running code switched to the new thing.

While here, fix a couple style issues in `rabbit_core_ff`.

Author: dumbbell

deps/rabbit/src/rabbit_core_ff.erl

@@ -88,7 +88,9 @@ quorum_queue_migration(_FeatureName, _FeatureProps, is_enabled) ->
     rabbit_table:wait(Tables, _Retry = true),
     Fields = amqqueue:fields(amqqueue_v2),
     mnesia:table_info(rabbit_queue, attributes) =:= Fields andalso
-    mnesia:table_info(rabbit_durable_queue, attributes) =:= Fields.
+    mnesia:table_info(rabbit_durable_queue, attributes) =:= Fields;
+quorum_queue_migration(_FeatureName, _FeatureProps, post_enabled_locally) ->
+    ok.
 
 stream_queue_migration(_FeatureName, _FeatureProps, _Enable) ->
     ok.
@@ -122,9 +124,12 @@ implicit_default_bindings_migration(FeatureName, _FeatureProps,
     rabbit_table:wait([rabbit_queue]),
     Queues = mnesia:dirty_all_keys(rabbit_queue),
     remove_explicit_default_bindings(FeatureName, Queues);
-implicit_default_bindings_migration(_Feature_Name, _FeatureProps,
+implicit_default_bindings_migration(_FeatureName, _FeatureProps,
                                     is_enabled) ->
-    undefined.
+    undefined;
+implicit_default_bindings_migration(_FeatureName, _FeatureProps,
+                                    post_enabled_locally) ->
+    ok.
 
 remove_explicit_default_bindings(_FeatureName, []) ->
     ok;
@@ -150,7 +155,10 @@ virtual_host_metadata_migration(_FeatureName, _FeatureProps, enable) ->
         {aborted, Reason} -> {error, Reason}
     end;
 virtual_host_metadata_migration(_FeatureName, _FeatureProps, is_enabled) ->
-    mnesia:table_info(rabbit_vhost, attributes) =:= vhost:fields(vhost_v2).
+    mnesia:table_info(rabbit_vhost, attributes) =:= vhost:fields(vhost_v2);
+virtual_host_metadata_migration(
+  _FeatureName, _FeatureProps, post_enabled_locally) ->
+    ok.
 
 %% -------------------------------------------------------------------
 %% Maintenance mode.
@@ -172,7 +180,10 @@ maintenance_mode_status_migration(FeatureName, _FeatureProps, enable) ->
           [Reason])
     end;
 maintenance_mode_status_migration(_FeatureName, _FeatureProps, is_enabled) ->
-    rabbit_table:exists(rabbit_maintenance:status_table_name()).
+    rabbit_table:exists(rabbit_maintenance:status_table_name());
+maintenance_mode_status_migration(
+  _FeatureName, _FeatureProps, post_enabled_locally) ->
+    ok.
 
 %% -------------------------------------------------------------------
 %% User limits.
@@ -182,9 +193,14 @@ user_limits_migration(_FeatureName, _FeatureProps, enable) ->
     Tab = rabbit_user,
     rabbit_table:wait([Tab], _Retry = true),
     Fun = fun(Row) -> internal_user:upgrade_to(internal_user_v2, Row) end,
-    case mnesia:transform_table(Tab, Fun, internal_user:fields(internal_user_v2)) of
+    Ret = mnesia:transform_table(
+            Tab, Fun, internal_user:fields(internal_user_v2)),
+    case Ret of
         {atomic, ok}      -> ok;
         {aborted, Reason} -> {error, Reason}
     end;
 user_limits_migration(_FeatureName, _FeatureProps, is_enabled) ->
-    mnesia:table_info(rabbit_user, attributes) =:= internal_user:fields(internal_user_v2).
+    mnesia:table_info(rabbit_user, attributes) =:=
+    internal_user:fields(internal_user_v2);
+user_limits_migration(_FeatureName, _FeatureProps, post_enabled_locally) ->
+    ok.

deps/rabbit/src/rabbit_feature_flags.erl

@@ -77,6 +77,8 @@
 
 -module(rabbit_feature_flags).
 
+-include_lib("stdlib/include/assert.hrl").
+
 -export([list/0,
          list/1,
          list/2,
@@ -1650,7 +1652,7 @@ mark_as_enabled(FeatureName, IsEnabled) ->
     end.
 
 -spec mark_as_enabled_locally(feature_name(), feature_state()) ->
-    any() | {error, any()} | no_return().
+    ok | {error, any()} | no_return().
 %% @private
 
 mark_as_enabled_locally(FeatureName, IsEnabled) ->
@@ -1673,9 +1675,20 @@ mark_as_enabled_locally(FeatureName, IsEnabled) ->
                             ok =:= try_to_write_enabled_feature_flags_list(
                                      NewEnabledFeatureNames)
                     end,
-    initialize_registry(#{},
-                        #{FeatureName => IsEnabled},
-                        WrittenToDisk).
+    Ret = initialize_registry(#{},
+                              #{FeatureName => IsEnabled},
+                              WrittenToDisk),
+    case Ret of
+        ok when IsEnabled ->
+            ?assert(is_enabled(FeatureName, non_blocking)),
+            spawn(
+              fun() ->
+                      _ = run_migration_fun(FeatureName, post_enabled_locally)
+              end);
+        _ ->
+            ok
+    end,
+    Ret.
 
 -spec mark_as_enabled_remotely(feature_name(), feature_state()) ->
     any() | {error, any()} | no_return().