feat(resource): reset metrics when stopping a resource

apps/emqx_resource/src/emqx_resource_manager.erl

@@ -507,13 +507,16 @@ start_resource(Data, From) ->
 
 stop_resource(#data{state = undefined, id = ResId} = _Data) ->
     _ = maybe_clear_alarm(ResId),
+    ok = emqx_metrics_worker:reset_metrics(?RES_METRICS, ResId),
     ok;
 stop_resource(Data) ->
     %% We don't care the return value of the Mod:on_stop/2.
     %% The callback mod should make sure the resource is stopped after on_stop/2
     %% is returned.
+    ResId = Data#data.id,
     _ = emqx_resource:call_stop(Data#data.manager_id, Data#data.mod, Data#data.state),
-    _ = maybe_clear_alarm(Data#data.id),
+    _ = maybe_clear_alarm(ResId),
+    ok = emqx_metrics_worker:reset_metrics(?RES_METRICS, ResId),
     ok.
 
 make_test_id() ->

apps/emqx_resource/test/emqx_resource_SUITE.erl

@@ -502,6 +502,10 @@ t_stop_start(_) ->
         #{<<"name">> => <<"test_resource">>}
     ),
 
+    %% add some metrics to test their persistence
+    emqx_resource_metrics:batching_change(?ID, 5),
+    ?assertEqual(5, emqx_resource_metrics:batching_get(?ID)),
+
     {ok, _} = emqx_resource:check_and_recreate(
         ?ID,
         ?TEST_RESOURCE,
@@ -513,6 +517,9 @@ t_stop_start(_) ->
 
     ?assert(is_process_alive(Pid0)),
 
+    %% metrics are reset when recreating
+    ?assertEqual(0, emqx_resource_metrics:batching_get(?ID)),
+
     ok = emqx_resource:stop(?ID),
 
     ?assertNot(is_process_alive(Pid0)),
@@ -527,7 +534,15 @@ t_stop_start(_) ->
 
     {ok, #{pid := Pid1}} = emqx_resource:query(?ID, get_state),
 
-    ?assert(is_process_alive(Pid1)).
+    ?assert(is_process_alive(Pid1)),
+
+    %% now stop while resetting the metrics
+    emqx_resource_metrics:batching_change(?ID, 5),
+    ?assertEqual(5, emqx_resource_metrics:batching_get(?ID)),
+    ok = emqx_resource:stop(?ID),
+    ?assertEqual(0, emqx_resource_metrics:batching_get(?ID)),
+
+    ok.
 
 t_stop_start_local(_) ->
     {error, _} = emqx_resource:check_and_create_local(