Stop stats only if they have been initialised

* Detected on unit tests, it should never happen on a rabbit node

Author: dcorbacho

src/gen_server2.erl

@@ -708,9 +708,9 @@ hibernate(GS2State = #gs2_state { timeout_state = TimeoutState }) ->
     proc_lib:hibernate(?MODULE, wake_hib,
                        [GS2State #gs2_state { timeout_state = TS }]).
 
-pre_hibernate(GS2State = #gs2_state { state   = State,
-                                      mod     = Mod }) ->
-    rabbit_event:stop_stats_timer(GS2State, #gs2_state.timer),
+pre_hibernate(GS2State0 = #gs2_state { state   = State,
+                                       mod     = Mod }) ->
+    GS2State = maybe_stop_stats(GS2State0),
     case erlang:function_exported(Mod, handle_pre_hibernate, 1) of
         true ->
             case catch Mod:handle_pre_hibernate(State) of
@@ -723,18 +723,19 @@ pre_hibernate(GS2State = #gs2_state { state   = State,
             hibernate(GS2State)
     end.
 
-post_hibernate(GS2State = #gs2_state { state = State,
-                                       mod   = Mod,
-                                       init_stats_fun = InitStatsFun }) ->
+post_hibernate(GS2State0 = #gs2_state { state = State,
+                                        mod   = Mod,
+                                        init_stats_fun = InitStatsFun }) ->
+    GS2State = InitStatsFun(GS2State0),
     case erlang:function_exported(Mod, handle_post_hibernate, 1) of
         true ->
             case catch Mod:handle_post_hibernate(State) of
                 {noreply, NState} ->
-                    process_next_msg(InitStatsFun(GS2State #gs2_state { state = NState,
-                                                                        time  = infinity }));
+                    process_next_msg(GS2State #gs2_state { state = NState,
+                                                           time  = infinity });
                 {noreply, NState, Time} ->
-                    process_next_msg(InitStatsFun(GS2State #gs2_state { state = NState,
-                                                                        time  = Time }));
+                    process_next_msg(GS2State #gs2_state { state = NState,
+                                                           time  = Time });
                 Reply ->
                     handle_common_termination(Reply, post_hibernate, GS2State)
             end;
@@ -745,7 +746,7 @@ post_hibernate(GS2State = #gs2_state { state = State,
             %% still set to hibernate, iff that msg is the very msg
             %% that woke us up (or the first msg we receive after
             %% waking up).
-            process_next_msg(InitStatsFun(GS2State #gs2_state { time = hibernate }))
+            process_next_msg(GS2State #gs2_state { time = hibernate })
     end.
 
 adjust_timeout_state(SleptAt, AwokeAt, {backoff, CurrentTO, MinimumTO,
@@ -1383,5 +1384,10 @@ emit_stats(GS2State = #gs2_state{queue = Queue}) ->
       #gs2_state.timer, emit_gen_server2_stats).
 
 stop_stats(GS2State) ->
-    _ = rabbit_event:stop_stats_timer(GS2State, #gs2_state.timer),
+    maybe_stop_stats(GS2State),
     rabbit_core_metrics:gen_server2_deleted(self()).
+
+maybe_stop_stats(#gs2_state{timer = undefined} = GS2State) ->
+    GS2State;
+maybe_stop_stats(GS2State) ->
+    rabbit_event:stop_stats_timer(GS2State, #gs2_state.timer).