If a queue process is hibernated, consider it up (#7825)

`rabbit_core_metrics_gc` checks the status of all queues (and other
things) every two minutes. With many queues, this can get pretty
expensive. Systems with lots of queues will often have many of them idle
and hibernated. Before this change `rabbit_core_metrics_gc` would wake
up all of them, causing a memory spike, just to check if their state
isn't `down`. With this change, a hibernated queue will be considered
up.

Author: mkuratczyk

deps/rabbit/src/rabbit_amqqueue.erl

@@ -1077,14 +1077,17 @@ list_local_names_down() ->
                               is_down(Q)].
 
 is_down(Q) ->
-    try
-        info(Q, [state]) == [{state, down}]
-    catch
-        _:_ ->
-            true
+    case rabbit_process:is_process_hibernated(amqqueue:get_pid(Q)) of
+        true -> false;
+        false ->
+            try
+                    info(Q, [state]) == [{state, down}]
+            catch
+                _:_ ->
+                    true
+            end
     end.
 
-
 -spec sample_local_queues() -> [amqqueue:amqqueue()].
 sample_local_queues() -> sample_n_by_name(list_local_names(), 300).
 

deps/rabbit/src/rabbit_process.erl

@@ -9,6 +9,7 @@
 
 -export([on_running_node/1,
          is_process_alive/1,
+         is_process_hibernated/1,
          is_registered_process_alive/1]).
 
 -spec on_running_node(Pid) -> OnRunningNode when
@@ -75,3 +76,15 @@ is_process_alive({Name, Node}) when is_atom(Name) andalso is_atom(Node) ->
 
 is_registered_process_alive(Name) ->
     is_pid(whereis(Name)).
+
+-spec is_process_hibernated(Pid) -> IsHibernated when
+      Pid :: pid(),
+      IsHibernated :: boolean().
+%% @doc Indicates if the specified process is hibernated.
+%%
+%% @param Pid the PID or name of the process to check
+%% @returns true if the process is hibernated on one of the cluster members,
+%% false otherwise.
+
+is_process_hibernated(Pid) when is_pid(Pid) ->
+    {current_function,{erlang,hibernate,3}} == erlang:process_info(Pid, current_function).