fix: monitor crash by ets badarg

apps/emqx_dashboard/src/emqx_dashboard_monitor.erl

@@ -26,21 +26,23 @@
 
 -export([start_link/0]).
 
--export([ init/1
-        , handle_call/3
-        , handle_cast/2
-        , handle_info/2
-        , terminate/2
-        , code_change/3
+-export([
+    init/1,
+    handle_call/3,
+    handle_cast/2,
+    handle_info/2,
+    terminate/2,
+    code_change/3
 ]).
 
 -export([mnesia/1]).
 
--export([ samplers/0
-        , samplers/2
-        , current_rate/0
-        , current_rate/1
-        , granularity_adapter/1
+-export([
+    samplers/0,
+    samplers/2,
+    current_rate/0,
+    current_rate/1,
+    granularity_adapter/1
 ]).
 
 %% for rpc
@@ -68,7 +70,8 @@ mnesia(boot) ->
         {local_content, true},
         {storage, disc_copies},
         {record_name, emqx_monit},
-        {attributes, record_info(fields, emqx_monit)}]).
+        {attributes, record_info(fields, emqx_monit)}
+    ]).
 
 %% -------------------------------------------------------------------------------------------------
 %% API
@@ -133,11 +136,15 @@ current_rate(Node) when Node == node() ->
     try
         {ok, Rate} = do_call(current_rate),
         {ok, Rate}
-    catch _E:R ->
+    catch
+        _E:R ->
             ?SLOG(warning, #{msg => "Dashboard monitor error", reason => R}),
             %% Rate map 0, ensure api will not crash.
             %% When joining cluster, dashboard monitor restart.
-        Rate0 = [{Key, 0} || Key <- ?GAUGE_SAMPLER_LIST ++ maps:values(?DELTA_SAMPLER_RATE_MAP)],
+            Rate0 = [
+                {Key, 0}
+             || Key <- ?GAUGE_SAMPLER_LIST ++ maps:values(?DELTA_SAMPLER_RATE_MAP)
+            ],
             {ok, maps:from_list(Rate0)}
     end;
 current_rate(Node) ->
@@ -175,12 +182,10 @@ handle_info({sample, Time}, State = #state{last = Last}) ->
     {atomic, ok} = flush(Last, Now),
     sample_timer(),
     {noreply, State#state{last = Now}};
-
 handle_info(clean_expired, State) ->
     clean(),
     clean_timer(),
     {noreply, State};
-
 handle_info(_Info, State = #state{}) ->
     {noreply, State}.
 
@@ -256,8 +261,10 @@ format(TimeStamp, Data, All) ->
 cal_rate(_Now, undefined) ->
     AllSamples = ?GAUGE_SAMPLER_LIST ++ maps:values(?DELTA_SAMPLER_RATE_MAP),
     lists:foldl(fun(Key, Acc) -> Acc#{Key => 0} end, #{}, AllSamples);
-cal_rate( #emqx_monit{data = NowData, time = NowTime}
-        , #emqx_monit{data = LastData, time = LastTime}) ->
+cal_rate(
+    #emqx_monit{data = NowData, time = NowTime},
+    #emqx_monit{data = LastData, time = LastTime}
+) ->
     TimeDelta = NowTime - LastTime,
     Filter = fun(Key, _) -> lists:member(Key, ?GAUGE_SAMPLER_LIST) end,
     Gauge = maps:filter(Filter, NowData),
@@ -340,9 +347,12 @@ clean() ->
     Now = erlang:system_time(millisecond),
     ExpiredMS = [{{'_', '$1', '_'}, [{'>', {'-', Now, '$1'}, ?RETENTION_TIME}], ['$_']}],
     Expired = ets:select(?TAB, ExpiredMS),
-    lists:foreach(fun(Data) ->
+    lists:foreach(
+        fun(Data) ->
             true = ets:delete_object(?TAB, Data)
-    end, Expired),
+        end,
+        Expired
+    ),
     ok.
 
 %% To make it easier to do data aggregation
@@ -364,8 +374,10 @@ count_map(M1, M2) ->
 
 getstats(Key) ->
     %% Stats ets maybe not exist when ekka join.
-    try stats(Key)
-    catch _: _ -> 0
+    try
+        stats(Key)
+    catch
+        _:_ -> 0
     end.
 
 stats(connections) -> emqx_stats:getstat('connections.count');