Merge pull request #12738 from rabbitmq/mergify/bp/v4.0.x/pr-12674

rabbit_amqqueue: Add `is_feature_used` callback to `transient_nonexcl_queues` depr. feature (backport #12674)

deps/rabbit/src/rabbit_amqqueue.erl

@@ -76,6 +76,9 @@
 -export([internal_declare/2, internal_delete/2, run_backing_queue/3,
          emit_consumers_local/3, internal_delete/3]).
 
+%% Deprecated feature callback.
+-export([are_transient_nonexcl_used/1]).
+
 -include_lib("rabbit_common/include/rabbit.hrl").
 -include_lib("stdlib/include/qlc.hrl").
 -include("amqqueue.hrl").
@@ -110,9 +113,19 @@
 -rabbit_deprecated_feature(
    {transient_nonexcl_queues,
     #{deprecation_phase => permitted_by_default,
-      doc_url => "https://blog.rabbitmq.com/posts/2021/08/4.0-deprecation-announcements/#removal-of-transient-non-exclusive-queues"
+      doc_url => "https://blog.rabbitmq.com/posts/2021/08/4.0-deprecation-announcements/#removal-of-transient-non-exclusive-queues",
+      callbacks => #{is_feature_used => {?MODULE, are_transient_nonexcl_used}}
      }}).
 
+are_transient_nonexcl_used(_) ->
+    case rabbit_db_queue:list_transient() of
+        {ok, Queues} ->
+            NonExclQueues = [Q || Q <- Queues, not is_exclusive(Q)],
+            length(NonExclQueues) > 0;
+        {error, _} ->
+            undefined
+    end.
+
 -define(CONSUMER_INFO_KEYS,
         [queue_name, channel_pid, consumer_tag, ack_required, prefetch_count,
          active, activity_status, arguments]).

deps/rabbit/src/rabbit_db_queue.erl

@@ -46,7 +46,8 @@
 
 %% Used by on_node_up and on_node_down.
 %% Can be deleted once transient entities/mnesia are removed.
--export([foreach_transient/1,
+-export([list_transient/0,
+         foreach_transient/1,
          delete_transient/1]).
 
 %% Only used by rabbit_amqqueue:forget_node_for_queue, which is only called
@@ -965,6 +966,40 @@ set_in_khepri(Q) ->
     Path = khepri_queue_path(amqqueue:get_name(Q)),
     rabbit_khepri:put(Path, Q).
 
+%% -------------------------------------------------------------------
+%% list_transient().
+%% -------------------------------------------------------------------
+
+-spec list_transient() -> {ok, Queues} | {error, any()} when
+      Queues :: [amqqueue:amqqueue()].
+%% @doc Applies `UpdateFun' to all transient queue records.
+%%
+%% @private
+
+list_transient() ->
+    rabbit_khepri:handle_fallback(
+      #{mnesia => fun() -> list_transient_in_mnesia() end,
+        khepri => fun() -> list_transient_in_khepri() end
+       }).
+
+list_transient_in_mnesia() ->
+    Pattern = amqqueue:pattern_match_all(),
+    AllQueues = mnesia:dirty_match_object(
+                  ?MNESIA_TABLE,
+                  Pattern),
+    {ok, AllQueues}.
+
+list_transient_in_khepri() ->
+    try
+        List = ets:match_object(
+                 ?KHEPRI_PROJECTION,
+                 amqqueue:pattern_match_on_durable(false)),
+        {ok, List}
+    catch
+        error:badarg ->
+            {error, {khepri_projection_missing, ?KHEPRI_WILDCARD_STAR}}
+    end.
+
 %% -------------------------------------------------------------------
 %% delete_transient().
 %% -------------------------------------------------------------------