fix(emqx_os_mon): log info level for unexpected message

also reply error for unexpected gen_server call
and refine log message for unexpected gen_server cast

apps/emqx/src/emqx_os_mon.erl

@@ -85,11 +85,10 @@ init([]) ->
     {ok, #{}}.
 
 handle_call(Req, _From, State) ->
-    ?LOG(error, "Unexpected call: ~p", [Req]),
-    {reply, ignored, State}.
+    {reply, {error, {unexpected_call, Req}}, State}.
 
 handle_cast(Msg, State) ->
-    ?LOG(error, "Unexpected cast: ~p", [Msg]),
+    ?LOG(error, "unexpected_cast_discarded: ~p", [Msg]),
     {noreply, State}.
 
 handle_info({timeout, _Timer, check}, State) ->
@@ -111,7 +110,7 @@ handle_info({timeout, _Timer, check}, State) ->
     {noreply, State};
 
 handle_info(Info, State) ->
-    ?LOG(error, "unexpected info: ~p", [Info]),
+    ?LOG(info, "unexpected_info_discarded: ~p", [Info]),
     {noreply, State}.
 
 terminate(_Reason, _State) ->

apps/emqx/test/emqx_os_mon_SUITE.erl

@@ -52,7 +52,8 @@ t_api(_) ->
     ?assertEqual(ok, emqx_os_mon:set_procmem_high_watermark(0.11)),
     ?assertEqual(11, emqx_os_mon:get_procmem_high_watermark()),
 
-    ?assertEqual(ignored, gen_server:call(emqx_os_mon, ignored)),
+    ?assertEqual({error, {unexpected_call, ignored}},
+                 gen_server:call(emqx_os_mon, ignored)),
     ?assertEqual(ok, gen_server:cast(emqx_os_mon, ignored)),
     emqx_os_mon ! ignored,
     gen_server:stop(emqx_os_mon),