Convert explicit default bindings removal to a feature flag

The feature flag is called `implicit_default_bindings`. It has the same
role as the previously existing upgrade function. The upgrade function
is removed in the process.

Compared to the upgrade function however, it does remove entries in the
`rabbit_route`, `rabbit_reverse_route` and `rabbit_semi_durable_route`
tables in addition to `rabbit_durable_route` table. Also, the list of
queues is taken from the `rabbit_queue` table instead of the
`rabbit_durable_queue` one.

[#163224049,#159298729]

3 files changed, 52 insertions, 25 deletions

diff --git a/src/rabbit_binding.erl b/src/rabbit_binding.erl
index 2b63b809b8..c4542abc61 100644
--- a/src/rabbit_binding.erl
+++ b/src/rabbit_binding.erl
@@ -257,7 +257,11 @@ remove(Src, Dst, B, ActingUser) ->
 remove_default_exchange_binding_rows_of(Dst = #resource{}) ->
     case rabbit_binding:implicit_for_destination(Dst) of
         [Binding] ->
-            mnesia:dirty_delete(rabbit_durable_route, Binding);
+            mnesia:dirty_delete(rabbit_durable_route, Binding),
+            mnesia:dirty_delete(rabbit_semi_durable_route, Binding),
+            mnesia:dirty_delete(rabbit_reverse_route,
+                                reverse_binding(Binding)),
+            mnesia:dirty_delete(rabbit_route, Binding);
         _ ->
             %% no binding to remove or
             %% a competing tx has beaten us to it?
diff --git a/src/rabbit_core_ff.erl b/src/rabbit_core_ff.erl
index 158eca4df8..a13099e304 100644
--- a/src/rabbit_core_ff.erl
+++ b/src/rabbit_core_ff.erl
@@ -16,7 +16,8 @@
 
 -module(rabbit_core_ff).
 
--export([quorum_queue_migration/3]).
+-export([quorum_queue_migration/3,
+         implicit_default_bindings_migration/3]).
 
 -rabbit_feature_flag(
    {quorum_queue,
@@ -26,13 +27,29 @@
       migration_fun => {?MODULE, quorum_queue_migration}
      }}).
 
+-rabbit_feature_flag(
+   {implicit_default_bindings,
+    #{desc          => "Default bindings are now implicit, instead of "
+                       "being stored in the database",
+      stability     => stable,
+      migration_fun => {?MODULE, implicit_default_bindings_migration}
+     }}).
+
+%% -------------------------------------------------------------------
+%% Quorum queues.
+%% -------------------------------------------------------------------
+
+-define(quorum_queue_tables, [rabbit_queue,
+                              rabbit_durable_queue]).
+
 quorum_queue_migration(FeatureName, _FeatureProps, enable) ->
-    Tables = [rabbit_queue,
-              rabbit_durable_queue],
+    Tables = ?quorum_queue_tables,
     rabbit_table:wait(Tables),
     Fields = amqqueue:fields(amqqueue_v2),
     migrate_to_amqqueue_with_type(FeatureName, Tables, Fields);
 quorum_queue_migration(_FeatureName, _FeatureProps, is_enabled) ->
+    Tables = ?quorum_queue_tables,
+    rabbit_table:wait(Tables),
     Fields = amqqueue:fields(amqqueue_v2),
     mnesia:table_info(rabbit_queue, attributes) =:= Fields andalso
     mnesia:table_info(rabbit_durable_queue, attributes) =:= Fields.
@@ -51,3 +68,30 @@ migrate_to_amqqueue_with_type(FeatureName, [], _) ->
     rabbit_log:info("Feature flag `~s`:   Mnesia tables migration done",
                     [FeatureName]),
     ok.
+
+%% -------------------------------------------------------------------
+%% Default bindings.
+%% -------------------------------------------------------------------
+
+implicit_default_bindings_migration(FeatureName, _FeatureProps,
+                                    enable) ->
+    %% Default exchange bindings are now implicit (not stored in the
+    %% route tables). It should be safe to remove them outside of a
+    %% transaction.
+    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,
+                                    is_enabled) ->
+    undefined.
+
+remove_explicit_default_bindings(_FeatureName, []) ->
+    ok;
+remove_explicit_default_bindings(FeatureName, Queues) ->
+    rabbit_log:info("Feature flag `~s`:   deleting explicit "
+                    "default bindings for ~b queues "
+                    "(it may take some time)...",
+                    [FeatureName, length(Queues)]),
+    [rabbit_binding:remove_default_exchange_binding_rows_of(Q)
+     || Q <- Queues],
+    ok.
diff --git a/src/rabbit_upgrade_functions.erl b/src/rabbit_upgrade_functions.erl
index 76a8b59e31..3072728d69 100644
--- a/src/rabbit_upgrade_functions.erl
+++ b/src/rabbit_upgrade_functions.erl
@@ -62,9 +62,6 @@
 -rabbit_upgrade({queue_options,         mnesia, [queue_vhost_field]}).
 -rabbit_upgrade({exchange_options,      mnesia, [operator_policies]}).
 
-%% TODO: move that to feature flags
--rabbit_upgrade({remove_explicit_default_exchange_bindings, mnesia, [queue_state]}).
-
 %% -------------------------------------------------------------------
 
 -spec remove_user_scope() -> 'ok'.
@@ -613,24 +610,6 @@ exchange_options(Table) ->
       [name, type, durable, auto_delete, internal, arguments, scratches, policy,
        operator_policy, decorators, options]).
 
-remove_explicit_default_exchange_bindings() ->
-    Tab = rabbit_durable_queue,
-    rabbit_table:wait([Tab]),
-    %% Default exchange bindings are now implicit
-    %% (not stored in the route tables).
-    %% It should be safe to remove them outside of a
-    %% transaction.
-    Queues = mnesia:dirty_all_keys(Tab),
-    N      = length(Queues),
-    case N of
-        0 -> ok;
-        _ ->
-            error_logger:info_msg("Will delete explicit default exchange bindings for ~p queues. "
-                                  "This can take some time...", [N]),
-            [rabbit_binding:remove_default_exchange_binding_rows_of(Q) || Q <- Queues]
-    end,
-    ok.
-
 %%--------------------------------------------------------------------
 
 transform(TableName, Fun, FieldList) ->