refactor(log-throttler): remove unnecessary code

there is no need to reset counters before erasing

apps/emqx/src/emqx_log_throttler.erl

@@ -49,8 +49,15 @@
 -define(MSGS_LIST, emqx:get_config([log, throttling, msgs], [])).
 -define(TIME_WINDOW_MS, timer:seconds(emqx:get_config([log, throttling, time_window], 60))).
 
--spec allow(atom(), any()) -> boolean().
-allow(Msg, UniqueKey) when is_atom(Msg) ->
+%% @doc Check if a throttled log message is allowed to pass down to the logger this time.
+%% The Msg has to be an atom, and the second argument `UniqueKey' should be `undefined'
+%% for predefined message IDs.
+%% For relatively static resources created from configurations such as data integration
+%% resource IDs `UniqueKey' should be of `binary()' type.
+-spec allow(atom(), undefined | binary()) -> boolean().
+allow(Msg, UniqueKey) when
+    is_atom(Msg) andalso (is_binary(UniqueKey) orelse UniqueKey =:= undefined)
+->
     case emqx_logger:get_primary_log_level() of
         debug ->
             true;
@@ -68,7 +75,7 @@ start_link() ->
 
 init([]) ->
     process_flag(trap_exit, true),
-    ok = lists:foreach(fun(Msg) -> new_throttler(Msg) end, ?MSGS_LIST),
+    ok = lists:foreach(fun new_throttler/1, ?MSGS_LIST),
     CurrentPeriodMs = ?TIME_WINDOW_MS,
     TimerRef = schedule_refresh(CurrentPeriodMs),
     {ok, #{timer_ref => TimerRef, current_period_ms => CurrentPeriodMs}}.
@@ -86,15 +93,16 @@ handle_info(refresh, #{current_period_ms := PeriodMs} = State) ->
     DroppedStats = lists:foldl(
         fun(Msg, Acc) ->
             case ?GET_SEQ(Msg) of
-                %% Should not happen, unless the static ids list is updated at run-time.
                 undefined ->
+                    %% Should not happen, unless the static ids list is updated at run-time.
                     new_throttler(Msg),
                     ?tp(log_throttler_new_msg, #{throttled_msg => Msg}),
                     Acc;
                 SeqMap when is_map(SeqMap) ->
                     maps:fold(
                         fun(Key, Ref, Acc0) ->
-                            drop_stats(Ref, emqx_utils:format("~ts:~s", [Msg, Key]), Acc0)
+                            ID = iolist_to_binary([atom_to_binary(Msg), $:, Key]),
+                            drop_stats(Ref, ID, Acc0)
                         end,
                         Acc,
                         SeqMap
@@ -124,27 +132,9 @@ drop_stats(SeqRef, Msg, Acc) ->
     maybe_add_dropped(Msg, Dropped, Acc).
 
 terminate(_Reason, _State) ->
-    lists:foreach(
-        fun(Msg) ->
-            case ?GET_SEQ(Msg) of
-                undefined ->
-                    ok;
-                SeqMap when is_map(SeqMap) ->
-                    maps:foreach(
-                        fun(_, Ref) ->
-                            ok = ?RESET_SEQ(Ref)
-                        end,
-                        SeqMap
-                    );
-                SeqRef ->
-                    %% atomics don't have erase API...
-                    %% (if nobody hold the ref, the atomics should erase automatically?)
-                    ok = ?RESET_SEQ(SeqRef)
-            end,
-            ?ERASE_SEQ(Msg)
-        end,
-        ?MSGS_LIST
-    ),
+    %% atomics do not have delete/remove/release/deallocate API
+    %% after the reference is garbage-collected the resource is released
+    lists:foreach(fun(Msg) -> ?ERASE_SEQ(Msg) end, ?MSGS_LIST),
     ok.
 
 code_change(_OldVsn, State, _Extra) ->
@@ -198,9 +188,9 @@ schedule_refresh(PeriodMs) ->
     erlang:send_after(PeriodMs, ?MODULE, refresh).
 
 new_throttler(unrecoverable_resource_error = Msg) ->
-    persistent_term:put(?SEQ_ID(Msg), #{});
+    new_throttler(Msg, #{});
 new_throttler(Msg) ->
-    persistent_term:put(?SEQ_ID(Msg), ?NEW_SEQ).
+    new_throttler(Msg, ?NEW_SEQ).
 
-new_throttler(Msg, Map) ->
-    persistent_term:put(?SEQ_ID(Msg), Map).
+new_throttler(Msg, AtomicOrEmptyMap) ->
+    persistent_term:put(?SEQ_ID(Msg), AtomicOrEmptyMap).

apps/emqx/test/emqx_log_throttler_SUITE.erl

@@ -127,7 +127,7 @@ t_throttle(_Config) ->
 
 t_throttle_recoverable_msg(_Config) ->
     ResourceId = <<"resource_id">>,
-    ThrottledMsg = emqx_utils:format("~ts:~s", [?THROTTLE_UNRECOVERABLE_MSG, ResourceId]),
+    ThrottledMsg = iolist_to_binary([atom_to_list(?THROTTLE_UNRECOVERABLE_MSG), ":", ResourceId]),
     ?check_trace(
         begin
             %% Warm-up and block to increase the probability that next events
@@ -181,10 +181,15 @@ t_throttle_add_new_msg(_Config) ->
 
 t_throttle_no_msg(_Config) ->
     %% Must simply pass with no crashes
+    Pid = erlang:whereis(emqx_log_throttler),
     ?assert(emqx_log_throttler:allow(no_test_throttle_msg, undefined)),
     ?assert(emqx_log_throttler:allow(no_test_throttle_msg, undefined)),
-    timer:sleep(10),
-    ?assert(erlang:is_process_alive(erlang:whereis(emqx_log_throttler))).
+    %% assert process is not restarted
+    ?assertEqual(Pid, erlang:whereis(emqx_log_throttler)),
+    %% make a gen_call to ensure the process is alive
+    %% note: this call result in an 'unexpected_call' error log.
+    ?assertEqual(ignored, gen_server:call(Pid, probe)),
+    ok.
 
 t_update_time_window(_Config) ->
     ?check_trace(