diff --git a/apps/emqx_auth_http/src/emqx_auth_http.appup.src b/apps/emqx_auth_http/src/emqx_auth_http.appup.src
index 8ebc195dd..b6d11dd8c 100644
--- a/apps/emqx_auth_http/src/emqx_auth_http.appup.src
+++ b/apps/emqx_auth_http/src/emqx_auth_http.appup.src
@@ -1,26 +1,16 @@
-%% -*-: erlang -*-
-
+%% -*- mode: erlang -*-
 {VSN,
-  [
-    {"4.3.2", [
-     {apply, {application, stop, [emqx_auth_http]}},
-     {load_module, emqx_auth_http_app, brutal_purge, soft_purge,[]},
-     {load_module, emqx_auth_http_cli, brutal_purge, soft_purge,[]}
-    ]},
-    {<<"4.3.[0-1]">>, [
-     {restart_application, emqx_auth_http}
-    ]},
-    {<<".*">>, []}
-  ],
-  [
-    {"4.3.2", [
-     {apply, {application, stop, [emqx_auth_http]}},
-     {load_module, emqx_auth_http_app, brutal_purge, soft_purge,[]},
-     {load_module, emqx_auth_http_cli, brutal_purge, soft_purge,[]}
-    ]},
-    {<<"4.3.[0-1]">>, [
-     {restart_application, emqx_auth_http}
-    ]},
-    {<<".*">>, []}
-  ]
-}.
+  [{"4.3.2",
+    [{apply,{application,stop,[emqx_auth_http]}},
+     {load_module,emqx_auth_http_app,brutal_purge,soft_purge,[]},
+     {load_module,emqx_auth_http_cli,brutal_purge,soft_purge,[]}]},
+   {<<"4.3.[0-1]">>,
+    [{restart_application,emqx_auth_http}]},
+   {<<".*">>,[]}],
+  [{"4.3.2",
+    [{apply,{application,stop,[emqx_auth_http]}},
+     {load_module,emqx_auth_http_app,brutal_purge,soft_purge,[]},
+     {load_module,emqx_auth_http_cli,brutal_purge,soft_purge,[]}]},
+   {<<"4.3.[0-1]">>,
+    [{restart_application,emqx_auth_http}]},
+   {<<".*">>,[]}]}.
diff --git a/apps/emqx_bridge_mqtt/src/emqx_bridge_mqtt.app.src b/apps/emqx_bridge_mqtt/src/emqx_bridge_mqtt.app.src
index 650c9d7fa..e6d1c55c4 100644
--- a/apps/emqx_bridge_mqtt/src/emqx_bridge_mqtt.app.src
+++ b/apps/emqx_bridge_mqtt/src/emqx_bridge_mqtt.app.src
@@ -1,6 +1,6 @@
 {application, emqx_bridge_mqtt,
  [{description, "EMQ X Bridge to MQTT Broker"},
-  {vsn, "4.3.2"}, % strict semver, bump manually!
+  {vsn, "4.3.3"}, % strict semver, bump manually!
   {modules, []},
   {registered, []},
   {applications, [kernel,stdlib,replayq,emqtt]},
diff --git a/apps/emqx_bridge_mqtt/src/emqx_bridge_mqtt.appup.src b/apps/emqx_bridge_mqtt/src/emqx_bridge_mqtt.appup.src
index b32d747f4..3b50949cd 100644
--- a/apps/emqx_bridge_mqtt/src/emqx_bridge_mqtt.appup.src
+++ b/apps/emqx_bridge_mqtt/src/emqx_bridge_mqtt.appup.src
@@ -1,18 +1,24 @@
 %% -*-: erlang -*-
 
-{VSN,
+{"4.3.3",
   [
+    {<<"4.3.[1-2]">>, [
+      {load_module, emqx_bridge_mqtt_actions, brutal_purge, soft_purge, []}
+    ]},
     {"4.3.0", [
-     {load_module, emqx_bridge_worker, brutal_purge, soft_purge, []}
-   ]},
-    {"4.3.1", []},
+      {load_module, emqx_bridge_worker, brutal_purge, soft_purge, []},
+      {load_module, emqx_bridge_mqtt_actions, brutal_purge, soft_purge, []}
+    ]},
     {<<".*">>, []}
   ],
   [
-    {"4.3.0", [
-     {load_module, emqx_bridge_worker, brutal_purge, soft_purge, []}
+    {<<"4.3.[1-2]">>, [
+      {load_module, emqx_bridge_mqtt_actions, brutal_purge, soft_purge, []}
+    ]},
+    {"4.3.0", [
+      {load_module, emqx_bridge_worker, brutal_purge, soft_purge, []},
+      {load_module, emqx_bridge_mqtt_actions, brutal_purge, soft_purge, []}
     ]},
-    {"4.3.1", []},
     {<<".*">>, []}
   ]
 }.
diff --git a/apps/emqx_bridge_mqtt/src/emqx_bridge_mqtt_actions.erl b/apps/emqx_bridge_mqtt/src/emqx_bridge_mqtt_actions.erl
index 3f685a72a..21cda5b6d 100644
--- a/apps/emqx_bridge_mqtt/src/emqx_bridge_mqtt_actions.erl
+++ b/apps/emqx_bridge_mqtt/src/emqx_bridge_mqtt_actions.erl
@@ -410,21 +410,35 @@ start_resource(ResId, PoolName, Options) ->
     end.
 
 test_resource_status(PoolName) ->
-    IsConnected = fun(Worker) ->
-                          case ecpool_worker:client(Worker) of
-                              {ok, Bridge} ->
-                                  try emqx_bridge_worker:status(Bridge) of
-                                      connected -> true;
-                                      _ -> false
-                                  catch _Error:_Reason ->
-                                          false
-                                  end;
-                              {error, _} ->
-                                  false
-                          end
-                  end,
-    Status = [IsConnected(Worker) || {_WorkerName, Worker} <- ecpool:workers(PoolName)],
-    lists:any(fun(St) -> St =:= true end, Status).
+    Parent = self(),
+    Pids = [spawn(fun() -> Parent ! {self(), get_worker_status(Worker)} end)
+            || {_WorkerName, Worker} <- ecpool:workers(PoolName)],
+    try
+        Status = [
+            receive {Pid, R} -> R
+            after 1000 -> %% get_worker_status/1 should be a quick operation
+                throw({timeout, Pid})
+            end || Pid <- Pids],
+        lists:any(fun(St) -> St =:= true end, Status)
+    catch
+        throw:Reason ->
+            ?LOG(error, "Get mqtt bridge status timeout: ~p", [Reason]),
+            lists:foreach(fun(Pid) -> exit(Pid, kill) end, Pids),
+            false
+    end.
+
+get_worker_status(Worker) ->
+    case ecpool_worker:client(Worker) of
+        {ok, Bridge} ->
+            try emqx_bridge_worker:status(Bridge) of
+                connected -> true;
+                _ -> false
+            catch _Error:_Reason ->
+                    false
+            end;
+        {error, _} ->
+            false
+    end.
 
 -spec(on_get_resource_status(ResId::binary(), Params::map()) -> Status::map()).
 on_get_resource_status(_ResId, #{<<"pool">> := PoolName}) ->
@@ -433,13 +447,13 @@ on_get_resource_status(_ResId, #{<<"pool">> := PoolName}) ->
 
 on_resource_destroy(ResId, #{<<"pool">> := PoolName}) ->
     ?LOG(info, "Destroying Resource ~p, ResId: ~p", [?RESOURCE_TYPE_MQTT, ResId]),
-        case ecpool:stop_sup_pool(PoolName) of
-            ok ->
-                ?LOG(info, "Destroyed Resource ~p Successfully, ResId: ~p", [?RESOURCE_TYPE_MQTT, ResId]);
-            {error, Reason} ->
-                ?LOG(error, "Destroy Resource ~p failed, ResId: ~p, ~p", [?RESOURCE_TYPE_MQTT, ResId, Reason]),
-                error({{?RESOURCE_TYPE_MQTT, ResId}, destroy_failed})
-        end.
+    case ecpool:stop_sup_pool(PoolName) of
+        ok ->
+            ?LOG(info, "Destroyed Resource ~p Successfully, ResId: ~p", [?RESOURCE_TYPE_MQTT, ResId]);
+        {error, Reason} ->
+            ?LOG(error, "Destroy Resource ~p failed, ResId: ~p, ~p", [?RESOURCE_TYPE_MQTT, ResId, Reason]),
+            error({{?RESOURCE_TYPE_MQTT, ResId}, destroy_failed})
+    end.
 
 on_action_create_data_to_mqtt_broker(ActId, Opts = #{<<"pool">> := PoolName,
                                                      <<"forward_topic">> := ForwardTopic,
diff --git a/apps/emqx_lwm2m/src/emqx_lwm2m.appup.src b/apps/emqx_lwm2m/src/emqx_lwm2m.appup.src
index 6656eb149..c2b7e7bc4 100644
--- a/apps/emqx_lwm2m/src/emqx_lwm2m.appup.src
+++ b/apps/emqx_lwm2m/src/emqx_lwm2m.appup.src
@@ -1,27 +1,16 @@
-%% -*-: erlang -*-
+%% -*- mode: erlang -*-
 {VSN,
-  [
-    {<<"4\\.3\\.[0-1]">>, [
-      {restart_application, emqx_lwm2m}
-    ]},
-    {"4.3.2", [
-      {load_module, emqx_lwm2m_message, brutal_purge, soft_purge, []}
-    ]},
-    {"4.3.3", []}, %% only config change
-    {"4.3.4", [
-      {load_module, emqx_lwm2m_protocol, brutal_purge, soft_purge, []}
-    ]}
-  ],
-  [
-    {<<"4\\.3\\.[0-1]">>, [
-      {restart_application, emqx_lwm2m}
-    ]},
-    {"4.3.2", [
-      {load_module, emqx_lwm2m_message, brutal_purge, soft_purge, []}
-    ]},
-    {"4.3.3", []}, %% only config change
-    {"4.3.4", [
-      {load_module, emqx_lwm2m_protocol, brutal_purge, soft_purge, []}
-    ]}
-  ]
-}.
+  [{<<"4\\.3\\.[0-1]">>,
+    [{restart_application,emqx_lwm2m}]},
+   {"4.3.2",
+    [{load_module,emqx_lwm2m_protocol,brutal_purge,soft_purge,[]},
+     {load_module,emqx_lwm2m_message,brutal_purge,soft_purge,[]}]},
+   {"4.3.3",[{load_module,emqx_lwm2m_protocol,brutal_purge,soft_purge,[]}]},
+   {"4.3.4",[{load_module,emqx_lwm2m_protocol,brutal_purge,soft_purge,[]}]}],
+  [{<<"4\\.3\\.[0-1]">>,
+    [{restart_application,emqx_lwm2m}]},
+   {"4.3.2",
+    [{load_module,emqx_lwm2m_protocol,brutal_purge,soft_purge,[]},
+     {load_module,emqx_lwm2m_message,brutal_purge,soft_purge,[]}]},
+   {"4.3.3",[{load_module,emqx_lwm2m_protocol,brutal_purge,soft_purge,[]}]},
+   {"4.3.4",[{load_module,emqx_lwm2m_protocol,brutal_purge,soft_purge,[]}]}]}.
diff --git a/apps/emqx_management/src/emqx_management.appup.src b/apps/emqx_management/src/emqx_management.appup.src
index e50724d6d..f0478add1 100644
--- a/apps/emqx_management/src/emqx_management.appup.src
+++ b/apps/emqx_management/src/emqx_management.appup.src
@@ -1,13 +1,13 @@
 %% -*- mode: erlang -*-
 {VSN,
- [ {<<"4\\.3\\.[0-7]+">>,
+ [ {<<"4\\.3\\.[0-8]+">>,
     [ {apply,{minirest,stop_http,['http:management']}},
       {apply,{minirest,stop_http,['https:management']}},
       {restart_application, emqx_management}
     ]},
    {<<".*">>, []}
  ],
- [ {<<"4\\.3\\.[0-7]+">>,
+ [ {<<"4\\.3\\.[0-8]+">>,
     [ {apply,{minirest,stop_http,['http:management']}},
       {apply,{minirest,stop_http,['https:management']}},
       {restart_application, emqx_management}
diff --git a/apps/emqx_management/src/emqx_mgmt.erl b/apps/emqx_management/src/emqx_mgmt.erl
index 61c32613b..8f871ecfc 100644
--- a/apps/emqx_management/src/emqx_mgmt.erl
+++ b/apps/emqx_management/src/emqx_mgmt.erl
@@ -124,6 +124,7 @@
 
 -define(APP, emqx_management).
 
+-elvis([{elvis_style, god_modules, disable}]).
 %%--------------------------------------------------------------------
 %% Node Info
 %%--------------------------------------------------------------------
@@ -143,7 +144,7 @@ node_info(Node) when Node =:= node() ->
     Info#{node              => node(),
           otp_release       => iolist_to_binary(otp_rel()),
           memory_total      => proplists:get_value(allocated, Memory),
-          memory_used       => proplists:get_value(total, Memory),
+          memory_used       => proplists:get_value(used, Memory),
           process_available => erlang:system_info(process_limit),
           process_used      => erlang:system_info(process_count),
           max_fds           => proplists:get_value(max_fds,
@@ -298,7 +299,7 @@ call_client(Node, ClientId, Req) when Node =:= node() ->
             Pid = lists:last(Pids),
             case emqx_cm:get_chan_info(ClientId, Pid) of
                 #{conninfo := #{conn_mod := ConnMod}} ->
-                    ConnMod:call(Pid, Req);
+                    erlang:apply(ConnMod, call, [Pid, Req]);
                 undefined -> {error, not_found}
             end
     end;
@@ -322,9 +323,10 @@ list_subscriptions_via_topic(Topic, FormatFun) ->
     lists:append([list_subscriptions_via_topic(Node, Topic, FormatFun)
         || Node <- ekka_mnesia:running_nodes()]).
 
+
 list_subscriptions_via_topic(Node, Topic, {M,F}) when Node =:= node() ->
     MatchSpec = [{{{'_', '$1'}, '_'}, [{'=:=','$1', Topic}], ['$_']}],
-    M:F(ets:select(emqx_suboption, MatchSpec));
+    erlang:apply(M, F, [ets:select(emqx_suboption, MatchSpec)]);
 
 list_subscriptions_via_topic(Node, Topic, FormatFun) ->
     rpc_call(Node, list_subscriptions_via_topic, [Node, Topic, FormatFun]).
diff --git a/apps/emqx_retainer/etc/emqx_retainer.conf b/apps/emqx_retainer/etc/emqx_retainer.conf
index 0a883cee5..8b5c251c6 100644
--- a/apps/emqx_retainer/etc/emqx_retainer.conf
+++ b/apps/emqx_retainer/etc/emqx_retainer.conf
@@ -39,3 +39,11 @@ retainer.max_payload_size = 1MB
 ##
 ## Defaut: 0
 retainer.expiry_interval = 0
+
+## When the retained flag of the PUBLISH message is set and Payload is empty,
+## whether to continue to publish the message.
+## see: http://docs.oasis-open.org/mqtt/mqtt/v3.1.1/os/mqtt-v3.1.1-os.html#_Toc398718038
+##
+## Value: Boolean
+## Default: false
+#retainer.stop_publish_clear_msg = false
diff --git a/apps/emqx_retainer/priv/emqx_retainer.schema b/apps/emqx_retainer/priv/emqx_retainer.schema
index e598864e1..5e998aa16 100644
--- a/apps/emqx_retainer/priv/emqx_retainer.schema
+++ b/apps/emqx_retainer/priv/emqx_retainer.schema
@@ -28,3 +28,10 @@
   {default, 0},
   {datatype, [integer, {duration, ms}]}
 ]}.
+
+%% Stop publish clear message
+%% {$configurable}
+{mapping, "retainer.stop_publish_clear_msg", "emqx_retainer.stop_publish_clear_msg", [
+  {default, false},
+  {datatype, {enum, [true, false]}}
+]}.
diff --git a/apps/emqx_retainer/src/emqx_retainer.appup.src b/apps/emqx_retainer/src/emqx_retainer.appup.src
index a17e6ee2f..19e8e835f 100644
--- a/apps/emqx_retainer/src/emqx_retainer.appup.src
+++ b/apps/emqx_retainer/src/emqx_retainer.appup.src
@@ -1,13 +1,13 @@
 %% -*-: erlang -*-
 {VSN,
   [
-    {"4.3.0", [
+    {<<"4\\.3\\.[0-1]+">>, [
       {load_module, emqx_retainer, brutal_purge, soft_purge, []}
     ]},
     {<<".*">>, []}
   ],
   [
-    {"4.3.0", [
+    {<<"4\\.3\\.[0-1]+">>, [
       {load_module, emqx_retainer, brutal_purge, soft_purge, []}
     ]},
     {<<".*">>, []}
diff --git a/apps/emqx_retainer/src/emqx_retainer.erl b/apps/emqx_retainer/src/emqx_retainer.erl
index b6de9d9f6..b99db5092 100644
--- a/apps/emqx_retainer/src/emqx_retainer.erl
+++ b/apps/emqx_retainer/src/emqx_retainer.erl
@@ -84,9 +84,14 @@ dispatch(Pid, Topic) ->
 %% RETAIN flag set to 1 and payload containing zero bytes
 on_message_publish(Msg = #message{flags   = #{retain := true},
                                   topic   = Topic,
-                                  payload = <<>>}, _Env) ->
+                                  payload = <<>>}, Env) ->
     mnesia:dirty_delete(?TAB, topic2tokens(Topic)),
-    {ok, Msg};
+    case stop_publish_clear_msg(Env) of
+        true ->
+            {ok, emqx_message:set_header(allow_publish, false, Msg)};
+        _ ->
+            {ok, Msg}
+    end;
 
 on_message_publish(Msg = #message{flags = #{retain := true}}, Env) ->
     Msg1 = emqx_message:set_header(retained, true, Msg),
@@ -229,6 +234,9 @@ store_retained(Msg = #message{topic = Topic, payload = Payload}, Env) ->
                         "for payload is too big!", [Topic, iolist_size(Payload)])
     end.
 
+stop_publish_clear_msg(Env) ->
+    proplists:get_bool(stop_publish_clear_msg, Env).
+
 is_table_full(Env) ->
     Limit = proplists:get_value(max_retained_messages, Env, 0),
     Limit > 0 andalso (retained_count() > Limit).
diff --git a/apps/emqx_retainer/test/emqx_retainer_SUITE.erl b/apps/emqx_retainer/test/emqx_retainer_SUITE.erl
index 1df042dd9..28f667b53 100644
--- a/apps/emqx_retainer/test/emqx_retainer_SUITE.erl
+++ b/apps/emqx_retainer/test/emqx_retainer_SUITE.erl
@@ -42,6 +42,8 @@ init_per_testcase(TestCase, Config) ->
     case TestCase of
         t_message_expiry_2 ->
             application:set_env(emqx_retainer, expiry_interval, 2000);
+        t_stop_publish_clear_msg ->
+            application:set_env(emqx_retainer, stop_publish_clear_msg, true);
         _ ->
             application:set_env(emqx_retainer, expiry_interval, 0)
     end,
@@ -173,6 +175,19 @@ t_clean(_) ->
 
     ok = emqtt:disconnect(C1).
 
+t_stop_publish_clear_msg(_) ->
+    {ok, C1} = emqtt:start_link([{clean_start, true}, {proto_ver, v5}]),
+    {ok, _} = emqtt:connect(C1),
+    emqtt:publish(C1, <<"retained/0">>, <<"this is a retained message 0">>, [{qos, 0}, {retain, true}]),
+
+    {ok, #{}, [0]} = emqtt:subscribe(C1, <<"retained/#">>, [{qos, 0}, {rh, 0}]),
+    ?assertEqual(1, length(receive_messages(1))),
+
+    emqtt:publish(C1, <<"retained/0">>, <<"">>, [{qos, 0}, {retain, true}]),
+    ?assertEqual(0, length(receive_messages(1))),
+
+    ok = emqtt:disconnect(C1).
+
 %%--------------------------------------------------------------------
 %% Helper functions
 %%--------------------------------------------------------------------
diff --git a/apps/emqx_sn/src/emqx_sn.app.src b/apps/emqx_sn/src/emqx_sn.app.src
index c48a76496..a36166eae 100644
--- a/apps/emqx_sn/src/emqx_sn.app.src
+++ b/apps/emqx_sn/src/emqx_sn.app.src
@@ -1,6 +1,6 @@
 {application, emqx_sn,
  [{description, "EMQ X MQTT-SN Plugin"},
-  {vsn, "4.3.3"}, % strict semver, bump manually!
+  {vsn, "4.3.4"}, % strict semver, bump manually!
   {modules, []},
   {registered, []},
   {applications, [kernel,stdlib,esockd]},
diff --git a/apps/emqx_sn/src/emqx_sn.appup.src b/apps/emqx_sn/src/emqx_sn.appup.src
index 2bd6f5646..0fbd16b1b 100644
--- a/apps/emqx_sn/src/emqx_sn.appup.src
+++ b/apps/emqx_sn/src/emqx_sn.appup.src
@@ -1,18 +1,24 @@
 %% -*-: erlang -*-
 {VSN,
  [
-   {"4.3.2", [
-     {load_module, emqx_sn_gateway, brutal_purge, soft_purge, []}
-   ]},
-   {<<"4.3.[0-1]">>, [
+    {"4.3.3", [
+      {load_module, emqx_sn_registry, brutal_purge, soft_purge, []}
+    ]},
+    {"4.3.2", [
+      {load_module, emqx_sn_gateway, brutal_purge, soft_purge, []}
+    ]},
+   {<<"4\\.3\\.[0-1]">>, [
      {restart_application, emqx_sn}
    ]}
  ],
  [
-   {"4.3.2", [
-     {load_module, emqx_sn_gateway, brutal_purge, soft_purge, []}
+   {"4.3.3", [
+      {load_module, emqx_sn_registry, brutal_purge, soft_purge, []}
    ]},
-   {<<"4.3.[0-1]">>, [
+   {"4.3.2", [
+      {load_module, emqx_sn_gateway, brutal_purge, soft_purge, []}
+    ]},
+   {<<"4\\.3\\.[0-1]">>, [
      {restart_application, emqx_sn}
    ]}
  ]
diff --git a/apps/emqx_sn/src/emqx_sn_registry.erl b/apps/emqx_sn/src/emqx_sn_registry.erl
index 4a3b22585..c97a49f5a 100644
--- a/apps/emqx_sn/src/emqx_sn_registry.erl
+++ b/apps/emqx_sn/src/emqx_sn_registry.erl
@@ -44,32 +44,16 @@
         , code_change/3
         ]).
 
+-ifdef(TEST).
+-export([create_table/0]).
+-endif.
+
 -define(TAB, ?MODULE).
 
 -record(state, {max_predef_topic_id = 0}).
 
 -record(emqx_sn_registry, {key, value}).
 
-%% Mnesia bootstrap
--export([mnesia/1]).
-
--boot_mnesia({mnesia, [boot]}).
--copy_mnesia({mnesia, [copy]}).
-
-
-%% @doc Create or replicate tables.
--spec(mnesia(boot | copy) -> ok).
-mnesia(boot) ->
-    %% Optimize storage
-    StoreProps = [{ets, [{read_concurrency, true}]}],
-    ok = ekka_mnesia:create_table(?MODULE, [
-            {attributes, record_info(fields, emqx_sn_registry)},
-            {ram_copies, [node()]},
-            {storage_properties, StoreProps}]);
-
-mnesia(copy) ->
-    ok = ekka_mnesia:copy_table(?MODULE, ram_copies).
-
 %%-----------------------------------------------------------------------------
 
 -spec(start_link(list()) -> {ok, pid()} | ignore | {error, Reason :: term()}).
@@ -123,6 +107,7 @@ unregister_topic(ClientId) ->
 %%-----------------------------------------------------------------------------
 
 init([PredefTopics]) ->
+    create_table(),
     %% {predef, TopicId}     -> TopicName
     %% {predef, TopicName}   -> TopicId
     %% {ClientId, TopicId}   -> TopicName
@@ -137,6 +122,15 @@ init([PredefTopics]) ->
                     end, 0, PredefTopics),
     {ok, #state{max_predef_topic_id = MaxPredefId}}.
 
+create_table() ->
+    %% Optimize storage
+    StoreProps = [{ets, [{read_concurrency, true}]}],
+    ok = ekka_mnesia:create_table(?MODULE, [
+        {attributes, record_info(fields, emqx_sn_registry)},
+        {ram_copies, [node()]},
+        {storage_properties, StoreProps}]),
+    ok = ekka_mnesia:copy_table(?MODULE, ram_copies).
+
 handle_call({register, ClientId, TopicName}, _From,
             State = #state{max_predef_topic_id = PredefId}) ->
     case lookup_topic_id(ClientId, TopicName) of
diff --git a/apps/emqx_sn/test/emqx_sn_registry_SUITE.erl b/apps/emqx_sn/test/emqx_sn_registry_SUITE.erl
index 8d320d8ed..023d83ae5 100644
--- a/apps/emqx_sn/test/emqx_sn_registry_SUITE.erl
+++ b/apps/emqx_sn/test/emqx_sn_registry_SUITE.erl
@@ -42,7 +42,7 @@ end_per_suite(_Config) ->
 
 init_per_testcase(_TestCase, Config) ->
     ekka_mnesia:start(),
-    emqx_sn_registry:mnesia(boot),
+    emqx_sn_registry:create_table(),
     mnesia:clear_table(emqx_sn_registry),
     PredefTopics = application:get_env(emqx_sn, predefined, []),
     {ok, _Pid} = ?REGISTRY:start_link(PredefTopics),
@@ -118,4 +118,3 @@ register_a_lot(N, Max) when N < Max ->
     Topic = iolist_to_binary(["Topic", integer_to_list(N)]),
     ?assertEqual(N, ?REGISTRY:register_topic(<<"ClientId">>, Topic)),
     register_a_lot(N+1, Max).
-
diff --git a/apps/emqx_stomp/src/emqx_stomp.appup.src b/apps/emqx_stomp/src/emqx_stomp.appup.src
index a29390bc1..0b5372dc9 100644
--- a/apps/emqx_stomp/src/emqx_stomp.appup.src
+++ b/apps/emqx_stomp/src/emqx_stomp.appup.src
@@ -1,16 +1,16 @@
 %% -*- mode: erlang -*-
 {VSN,
   [{"4.3.2",[{load_module,emqx_stomp_protocol,brutal_purge,soft_purge,[]}]},
-   {"4.3.1",[
-     {load_module,emqx_stomp_protocol,brutal_purge,soft_purge,[]},
+   {"4.3.1",
+    [{load_module,emqx_stomp_protocol,brutal_purge,soft_purge,[]},
      {load_module,emqx_stomp_connection,brutal_purge,soft_purge,[]}]},
    {"4.3.0",
     [{restart_application,emqx_stomp},
      {apply,{emqx_stomp,force_clear_after_app_stoped,[]}}]},
    {<<".*">>,[]}],
   [{"4.3.2",[{load_module,emqx_stomp_protocol,brutal_purge,soft_purge,[]}]},
-   {"4.3.1",[
-     {load_module,emqx_stomp_protocol,brutal_purge,soft_purge,[]},
+   {"4.3.1",
+    [{load_module,emqx_stomp_protocol,brutal_purge,soft_purge,[]},
      {load_module,emqx_stomp_connection,brutal_purge,soft_purge,[]}]},
    {"4.3.0",
     [{restart_application,emqx_stomp}]},
diff --git a/apps/emqx_web_hook/src/emqx_web_hook.appup.src b/apps/emqx_web_hook/src/emqx_web_hook.appup.src
index 40bdfbdbf..5c801d24a 100644
--- a/apps/emqx_web_hook/src/emqx_web_hook.appup.src
+++ b/apps/emqx_web_hook/src/emqx_web_hook.appup.src
@@ -4,25 +4,31 @@
     [{apply,{application,stop,[emqx_web_hook]}},
      {load_module,emqx_web_hook_app,brutal_purge,soft_purge,[]},
      {load_module,emqx_web_hook_actions,brutal_purge,soft_purge,[]}]},
-   {"4.3.5",[{load_module,emqx_web_hook_actions,brutal_purge,soft_purge,[]}]},
+   {"4.3.5",
+    [{load_module,emqx_web_hook_app,brutal_purge,soft_purge,[]},
+     {load_module,emqx_web_hook_actions,brutal_purge,soft_purge,[]}]},
    {<<"4.3.[0-2]">>,
     [{apply,{application,stop,[emqx_web_hook]}},
      {load_module,emqx_web_hook_app,brutal_purge,soft_purge,[]},
      {load_module,emqx_web_hook,brutal_purge,soft_purge,[]},
      {load_module,emqx_web_hook_actions,brutal_purge,soft_purge,[]}]},
    {<<"4.3.[3-4]">>,
-    [{load_module,emqx_web_hook_actions,brutal_purge,soft_purge,[]}]},
+    [{load_module,emqx_web_hook_app,brutal_purge,soft_purge,[]},
+     {load_module,emqx_web_hook_actions,brutal_purge,soft_purge,[]}]},
    {<<".*">>,[]}],
   [{"4.3.7",
     [{apply,{application,stop,[emqx_web_hook]}},
      {load_module,emqx_web_hook_app,brutal_purge,soft_purge,[]},
      {load_module,emqx_web_hook_actions,brutal_purge,soft_purge,[]}]},
-   {"4.3.5",[{load_module,emqx_web_hook_actions,brutal_purge,soft_purge,[]}]},
+   {"4.3.5",
+    [{load_module,emqx_web_hook_app,brutal_purge,soft_purge,[]},
+     {load_module,emqx_web_hook_actions,brutal_purge,soft_purge,[]}]},
    {<<"4.3.[0-2]">>,
     [{apply,{application,stop,[emqx_web_hook]}},
      {load_module,emqx_web_hook_app,brutal_purge,soft_purge,[]},
      {load_module,emqx_web_hook,brutal_purge,soft_purge,[]},
      {load_module,emqx_web_hook_actions,brutal_purge,soft_purge,[]}]},
    {<<"4.3.[3-4]">>,
-    [{load_module,emqx_web_hook_actions,brutal_purge,soft_purge,[]}]},
+    [{load_module,emqx_web_hook_app,brutal_purge,soft_purge,[]},
+     {load_module,emqx_web_hook_actions,brutal_purge,soft_purge,[]}]},
    {<<".*">>,[]}]}.
diff --git a/etc/emqx.conf b/etc/emqx.conf
index de5c062a4..d6bfcb137 100644
--- a/etc/emqx.conf
+++ b/etc/emqx.conf
@@ -668,9 +668,11 @@ mqtt.max_packet_size = 1MB
 mqtt.max_clientid_len = 65535
 
 ## Maximum topic levels allowed. 0 means no limit.
+## Depth so big may lead to subscribing performance issues.
 ##
-## Value: Number
-mqtt.max_topic_levels = 0
+## Value: Number [0-65535]
+## Default: 128
+mqtt.max_topic_levels = 128
 
 ## Maximum QoS allowed.
 ##
@@ -774,8 +776,9 @@ zone.external.force_gc_policy = 16000|16MB
 
 ## Maximum topic levels allowed. 0 means no limit.
 ##
-## Value: Number
-## zone.external.max_topic_levels = 7
+## Value: Number [0-65535]
+## Default: 7
+zone.external.max_topic_levels = 7
 
 ## Maximum QoS allowed.
 ##
diff --git a/priv/emqx.schema b/priv/emqx.schema
index facd86455..0aa77865c 100644
--- a/priv/emqx.schema
+++ b/priv/emqx.schema
@@ -830,7 +830,7 @@ end}.
 
 %% @doc Set the Maximum topic levels.
 {mapping, "mqtt.max_topic_levels", "emqx.max_topic_levels", [
-  {default, 0},
+  {default, 128},
   {datatype, integer}
 ]}.
 
diff --git a/rebar.config b/rebar.config
index cd2cf3a64..da51eec95 100644
--- a/rebar.config
+++ b/rebar.config
@@ -47,7 +47,7 @@
     , {gen_rpc, {git, "https://github.com/emqx/gen_rpc", {tag, "2.7.0"}}}
     , {cuttlefish, {git, "https://github.com/emqx/cuttlefish", {tag, "v3.3.6"}}}
     , {minirest, {git, "https://github.com/emqx/minirest", {tag, "0.3.7"}}}
-    , {ecpool, {git, "https://github.com/emqx/ecpool", {tag, "0.5.1"}}}
+    , {ecpool, {git, "https://github.com/emqx/ecpool", {tag, "0.5.2"}}}
     , {replayq, {git, "https://github.com/emqx/replayq", {tag, "0.3.2"}}}
     , {pbkdf2, {git, "https://github.com/emqx/erlang-pbkdf2.git", {branch, "2.0.4"}}}
     , {emqtt, {git, "https://github.com/emqx/emqtt", {tag, "1.2.3.1"}}}
diff --git a/scripts/update_appup.escript b/scripts/update_appup.escript
index 39a71b492..7674a941c 100755
--- a/scripts/update_appup.escript
+++ b/scripts/update_appup.escript
@@ -99,8 +99,26 @@ main(Options, Baseline) ->
                 [] ->
                     ok;
                 _ ->
-                    set_invalid(),
-                    log("ERROR: The appup files are incomplete. Missing changes:~n   ~p", [AppupChanges])
+                    Diffs =
+                        lists:filtermap(
+                          fun({App, {Upgrade, Downgrade, OldUpgrade, OldDowngrade}}) ->
+                                  case parse_appup_diffs(Upgrade, OldUpgrade,
+                                                         Downgrade, OldDowngrade) of
+                                      ok ->
+                                          false;
+                                      {diffs, Diffs} ->
+                                          {true, {App, Diffs}}
+                                  end
+                          end,
+                          AppupChanges),
+                    case Diffs =:= [] of
+                        true ->
+                            ok;
+                        false ->
+                            set_invalid(),
+                            log("ERROR: The appup files are incomplete. Missing changes:~n   ~p",
+                                [Diffs])
+                    end
             end;
         false ->
             update_appups(AppupChanges)
@@ -154,7 +172,7 @@ download_prev_release(Tag, #{binary_rel_url := {ok, URL0}, clone_url := Repo}) -
     Dir = filename:basename(Repo, ".git") ++ [$-|Tag],
     Filename = filename:join(BaseDir, Dir),
     Script = "mkdir -p ${OUTFILE} &&
-              wget -O ${OUTFILE}.zip ${URL} &&
+              wget -c -O ${OUTFILE}.zip ${URL} &&
               unzip -n -d ${OUTFILE} ${OUTFILE}.zip",
     Env = [{"TAG", Tag}, {"OUTFILE", Filename}, {"URL", URL}],
     bash(Script, Env),
@@ -189,9 +207,52 @@ find_appup_actions(App, CurrAppIdx, PrevAppIdx = #app{version = PrevVersion}) ->
             %% The appup file has been already updated:
             [];
        true ->
-            [{App, {Upgrade, Downgrade}}]
+            [{App, {Upgrade, Downgrade, OldUpgrade, OldDowngrade}}]
     end.
 
+%% For external dependencies, show only the changes that are missing
+%% in their current appup.
+diff_appup_instructions(ComputedChanges, PresentChanges) ->
+    lists:foldr(
+      fun({Vsn, ComputedActions}, Acc) ->
+              case find_matching_version(Vsn, PresentChanges) of
+                  undefined ->
+                      [{Vsn, ComputedActions} | Acc];
+                  PresentActions ->
+                      DiffActions = ComputedActions -- PresentActions,
+                      case DiffActions of
+                          [] ->
+                              %% no diff
+                              Acc;
+                          _ ->
+                              [{Vsn, DiffActions} | Acc]
+                      end
+              end
+      end,
+      [],
+      ComputedChanges).
+
+%% For external dependencies, checks if any missing diffs are present
+%% and groups them by `up' and `down' types.
+parse_appup_diffs(Upgrade, OldUpgrade, Downgrade, OldDowngrade) ->
+    DiffUp = diff_appup_instructions(Upgrade, OldUpgrade),
+    DiffDown = diff_appup_instructions(Downgrade, OldDowngrade),
+    case {DiffUp, DiffDown} of
+        {[], []} ->
+            %% no diff for external dependency; ignore
+            ok;
+        _ ->
+            set_invalid(),
+            Diffs = #{ up => DiffUp
+                     , down => DiffDown
+                     },
+            {diffs, Diffs}
+    end.
+
+%% TODO: handle regexes
+find_matching_version(Vsn, PresentChanges) ->
+    proplists:get_value(Vsn, PresentChanges).
+
 find_old_appup_actions(App, PrevVersion) ->
     {Upgrade0, Downgrade0} =
         case locate(ebin_current, App, ".appup") of
@@ -270,12 +331,12 @@ check_appup_files() ->
 
 update_appups(Changes) ->
     lists:foreach(
-      fun({App, {Upgrade, Downgrade}}) ->
-              do_update_appup(App, Upgrade, Downgrade)
+      fun({App, {Upgrade, Downgrade, OldUpgrade, OldDowngrade}}) ->
+              do_update_appup(App, Upgrade, Downgrade, OldUpgrade, OldDowngrade)
       end,
       Changes).
 
-do_update_appup(App, Upgrade, Downgrade) ->
+do_update_appup(App, Upgrade, Downgrade, OldUpgrade, OldDowngrade) ->
     case locate(src, App, ".appup.src") of
         {ok, AppupFile} ->
             render_appfile(AppupFile, Upgrade, Downgrade);
@@ -284,8 +345,16 @@ do_update_appup(App, Upgrade, Downgrade) ->
                 {ok, AppupFile} ->
                     render_appfile(AppupFile, Upgrade, Downgrade);
                 false ->
-                    set_invalid(),
-                    log("ERROR: Appup file for the external dependency '~p' is not complete.~n       Missing changes: ~p~n", [App, Upgrade])
+                    case parse_appup_diffs(Upgrade, OldUpgrade,
+                                           Downgrade, OldDowngrade) of
+                        ok ->
+                            %% no diff for external dependency; ignore
+                            ok;
+                        {diffs, Diffs} ->
+                            set_invalid(),
+                            log("ERROR: Appup file for the external dependency '~p' is not complete.~n       Missing changes: ~100p~n", [App, Diffs]),
+                            log("NOTE: Some changes above might be already covered by regexes.~n")
+                    end
             end
     end.
 
@@ -298,12 +367,14 @@ render_appfile(File, Upgrade, Downgrade) ->
     ok = file:write_file(File, IOList).
 
 create_stub(App) ->
-    case locate(src, App, ".app.src") of
+    case locate(src, App, Ext = ".app.src") of
         {ok, AppSrc} ->
-            AppupFile = filename:basename(AppSrc) ++ ".appup.src",
+            DirName = filename:dirname(AppSrc),
+            AppupFile = filename:basename(AppSrc, Ext) ++ ".appup.src",
             Default = {<<".*">>, []},
-            render_appfile(AppupFile, [Default], [Default]),
-            AppupFile;
+            AppupFileFullpath = filename:join(DirName, AppupFile),
+            render_appfile(AppupFileFullpath, [Default], [Default]),
+            {ok, AppupFileFullpath};
         undefined ->
             false
     end.
diff --git a/src/emqx.appup.src b/src/emqx.appup.src
index 653249ccb..c510b3043 100644
--- a/src/emqx.appup.src
+++ b/src/emqx.appup.src
@@ -1,13 +1,19 @@
 %% -*- mode: erlang -*-
 {VSN,
   [{"4.3.11",
-    [{load_module,emqx_http_lib,brutal_purge,soft_purge,[]}]},
+    [{load_module,emqx_vm,brutal_purge,soft_purge,[]},
+     {load_module,emqx_sys_mon,brutal_purge,soft_purge,[]},
+     {load_module,emqx_http_lib,brutal_purge,soft_purge,[]}]},
    {"4.3.10",
-    [{load_module,emqx_http_lib,brutal_purge,soft_purge,[]},
+    [{load_module,emqx_vm,brutal_purge,soft_purge,[]},
+     {load_module,emqx_sys_mon,brutal_purge,soft_purge,[]},
+     {load_module,emqx_http_lib,brutal_purge,soft_purge,[]},
      {load_module,emqx_app,brutal_purge,soft_purge,[]},
      {load_module,emqx_connection,brutal_purge,soft_purge,[]}]},
    {"4.3.9",
-    [{load_module,emqx_http_lib,brutal_purge,soft_purge,[]},
+    [{load_module,emqx_vm,brutal_purge,soft_purge,[]},
+     {load_module,emqx_sys_mon,brutal_purge,soft_purge,[]},
+     {load_module,emqx_http_lib,brutal_purge,soft_purge,[]},
      {load_module,emqx_connection,brutal_purge,soft_purge,[]},
      {load_module,emqx_channel,brutal_purge,soft_purge,[]},
      {load_module,emqx_cm,brutal_purge,soft_purge,[]},
@@ -18,7 +24,9 @@
      {load_module,emqx_rpc,brutal_purge,soft_purge,[]},
      {load_module,emqx_app,brutal_purge,soft_purge,[]}]},
    {"4.3.8",
-    [{load_module,emqx_http_lib,brutal_purge,soft_purge,[]},
+    [{load_module,emqx_vm,brutal_purge,soft_purge,[]},
+     {load_module,emqx_sys_mon,brutal_purge,soft_purge,[]},
+     {load_module,emqx_http_lib,brutal_purge,soft_purge,[]},
      {load_module,emqx_connection,brutal_purge,soft_purge,[]},
      {load_module,emqx_channel,brutal_purge,soft_purge,[]},
      {load_module,emqx_cm,brutal_purge,soft_purge,[]},
@@ -29,7 +37,9 @@
      {load_module,emqx_rpc,brutal_purge,soft_purge,[]},
      {load_module,emqx_app,brutal_purge,soft_purge,[]}]},
    {"4.3.7",
-    [{load_module,emqx_http_lib,brutal_purge,soft_purge,[]},
+    [{load_module,emqx_vm,brutal_purge,soft_purge,[]},
+     {load_module,emqx_sys_mon,brutal_purge,soft_purge,[]},
+     {load_module,emqx_http_lib,brutal_purge,soft_purge,[]},
      {load_module,emqx_connection,brutal_purge,soft_purge,[]},
      {load_module,emqx_channel,brutal_purge,soft_purge,[]},
      {load_module,emqx_cm,brutal_purge,soft_purge,[]},
@@ -42,7 +52,9 @@
      {load_module,emqx_rpc,brutal_purge,soft_purge,[]},
      {load_module,emqx_app,brutal_purge,soft_purge,[]}]},
    {"4.3.6",
-    [{load_module,emqx_http_lib,brutal_purge,soft_purge,[]},
+    [{load_module,emqx_vm,brutal_purge,soft_purge,[]},
+     {load_module,emqx_sys_mon,brutal_purge,soft_purge,[]},
+     {load_module,emqx_http_lib,brutal_purge,soft_purge,[]},
      {load_module,emqx_connection,brutal_purge,soft_purge,[]},
      {load_module,emqx_channel,brutal_purge,soft_purge,[]},
      {load_module,emqx_cm,brutal_purge,soft_purge,[]},
@@ -56,7 +68,9 @@
      {load_module,emqx_rpc,brutal_purge,soft_purge,[]},
      {load_module,emqx_app,brutal_purge,soft_purge,[]}]},
    {"4.3.5",
-    [{load_module,emqx_http_lib,brutal_purge,soft_purge,[]},
+    [{load_module,emqx_vm,brutal_purge,soft_purge,[]},
+     {load_module,emqx_sys_mon,brutal_purge,soft_purge,[]},
+     {load_module,emqx_http_lib,brutal_purge,soft_purge,[]},
      {load_module,emqx_connection,brutal_purge,soft_purge,[]},
      {load_module,emqx_channel,brutal_purge,soft_purge,[]},
      {load_module,emqx_ws_connection,brutal_purge,soft_purge,[]},
@@ -71,7 +85,9 @@
      {load_module,emqx_rpc,brutal_purge,soft_purge,[]},
      {load_module,emqx_app,brutal_purge,soft_purge,[]}]},
    {"4.3.4",
-    [{load_module,emqx_http_lib,brutal_purge,soft_purge,[]},
+    [{load_module,emqx_vm,brutal_purge,soft_purge,[]},
+     {load_module,emqx_sys_mon,brutal_purge,soft_purge,[]},
+     {load_module,emqx_http_lib,brutal_purge,soft_purge,[]},
      {load_module,emqx_connection,brutal_purge,soft_purge,[]},
      {load_module,emqx_channel,brutal_purge,soft_purge,[]},
      {load_module,emqx_ws_connection,brutal_purge,soft_purge,[]},
@@ -87,7 +103,9 @@
      {load_module,emqx_rpc,brutal_purge,soft_purge,[]},
      {load_module,emqx_app,brutal_purge,soft_purge,[]}]},
    {"4.3.3",
-    [{load_module,emqx_http_lib,brutal_purge,soft_purge,[]},
+    [{load_module,emqx_vm,brutal_purge,soft_purge,[]},
+     {load_module,emqx_sys_mon,brutal_purge,soft_purge,[]},
+     {load_module,emqx_http_lib,brutal_purge,soft_purge,[]},
      {load_module,emqx_connection,brutal_purge,soft_purge,[]},
      {load_module,emqx_channel,brutal_purge,soft_purge,[]},
      {load_module,emqx_alarm_handler,brutal_purge,soft_purge,[]},
@@ -104,7 +122,9 @@
      {load_module,emqx_rpc,brutal_purge,soft_purge,[]},
      {load_module,emqx_app,brutal_purge,soft_purge,[]}]},
    {"4.3.2",
-    [{load_module,emqx_alarm_handler,brutal_purge,soft_purge,[]},
+    [{load_module,emqx_vm,brutal_purge,soft_purge,[]},
+     {load_module,emqx_sys_mon,brutal_purge,soft_purge,[]},
+     {load_module,emqx_alarm_handler,brutal_purge,soft_purge,[]},
      {load_module,emqx_misc,brutal_purge,soft_purge,[]},
      {load_module,emqx_packet,brutal_purge,soft_purge,[]},
      {load_module,emqx_shared_sub,brutal_purge,soft_purge,[]},
@@ -121,7 +141,9 @@
      {load_module,emqx_rpc,brutal_purge,soft_purge,[]},
      {load_module,emqx_app,brutal_purge,soft_purge,[]}]},
    {"4.3.1",
-    [{load_module,emqx_alarm_handler,brutal_purge,soft_purge,[]},
+    [{load_module,emqx_vm,brutal_purge,soft_purge,[]},
+     {load_module,emqx_sys_mon,brutal_purge,soft_purge,[]},
+     {load_module,emqx_alarm_handler,brutal_purge,soft_purge,[]},
      {load_module,emqx_misc,brutal_purge,soft_purge,[]},
      {load_module,emqx_packet,brutal_purge,soft_purge,[]},
      {load_module,emqx_shared_sub,brutal_purge,soft_purge,[]},
@@ -142,7 +164,9 @@
      {load_module,emqx_rpc,brutal_purge,soft_purge,[]},
      {load_module,emqx_app,brutal_purge,soft_purge,[]}]},
    {"4.3.0",
-    [{load_module,emqx_pqueue,brutal_purge,soft_purge,[]},
+    [{load_module,emqx_vm,brutal_purge,soft_purge,[]},
+     {load_module,emqx_sys_mon,brutal_purge,soft_purge,[]},
+     {load_module,emqx_pqueue,brutal_purge,soft_purge,[]},
      {load_module,emqx_mqueue,brutal_purge,soft_purge,[]},
      {load_module,emqx_alarm_handler,brutal_purge,soft_purge,[]},
      {load_module,emqx_misc,brutal_purge,soft_purge,[]},
@@ -168,13 +192,19 @@
      {load_module,emqx_app,brutal_purge,soft_purge,[]}]},
    {<<".*">>,[]}],
   [{"4.3.11",
-    [{load_module,emqx_http_lib,brutal_purge,soft_purge,[]}]},
+    [{load_module,emqx_vm,brutal_purge,soft_purge,[]},
+     {load_module,emqx_sys_mon,brutal_purge,soft_purge,[]},
+     {load_module,emqx_http_lib,brutal_purge,soft_purge,[]}]},
    {"4.3.10",
-    [{load_module,emqx_http_lib,brutal_purge,soft_purge,[]},
+    [{load_module,emqx_vm,brutal_purge,soft_purge,[]},
+     {load_module,emqx_sys_mon,brutal_purge,soft_purge,[]},
+     {load_module,emqx_http_lib,brutal_purge,soft_purge,[]},
      {load_module,emqx_app,brutal_purge,soft_purge,[]},
      {load_module,emqx_connection,brutal_purge,soft_purge,[]}]},
    {"4.3.9",
-    [{load_module,emqx_http_lib,brutal_purge,soft_purge,[]},
+    [{load_module,emqx_vm,brutal_purge,soft_purge,[]},
+     {load_module,emqx_sys_mon,brutal_purge,soft_purge,[]},
+     {load_module,emqx_http_lib,brutal_purge,soft_purge,[]},
      {load_module,emqx_connection,brutal_purge,soft_purge,[]},
      {load_module,emqx_channel,brutal_purge,soft_purge,[]},
      {load_module,emqx_cm,brutal_purge,soft_purge,[]},
@@ -185,7 +215,9 @@
      {load_module,emqx_rpc,brutal_purge,soft_purge,[]},
      {load_module,emqx_app,brutal_purge,soft_purge,[]}]},
    {"4.3.8",
-    [{load_module,emqx_http_lib,brutal_purge,soft_purge,[]},
+    [{load_module,emqx_vm,brutal_purge,soft_purge,[]},
+     {load_module,emqx_sys_mon,brutal_purge,soft_purge,[]},
+     {load_module,emqx_http_lib,brutal_purge,soft_purge,[]},
      {load_module,emqx_connection,brutal_purge,soft_purge,[]},
      {load_module,emqx_channel,brutal_purge,soft_purge,[]},
      {load_module,emqx_cm,brutal_purge,soft_purge,[]},
@@ -196,7 +228,9 @@
      {load_module,emqx_rpc,brutal_purge,soft_purge,[]},
      {load_module,emqx_app,brutal_purge,soft_purge,[]}]},
    {"4.3.7",
-    [{load_module,emqx_http_lib,brutal_purge,soft_purge,[]},
+    [{load_module,emqx_vm,brutal_purge,soft_purge,[]},
+     {load_module,emqx_sys_mon,brutal_purge,soft_purge,[]},
+     {load_module,emqx_http_lib,brutal_purge,soft_purge,[]},
      {load_module,emqx_connection,brutal_purge,soft_purge,[]},
      {load_module,emqx_channel,brutal_purge,soft_purge,[]},
      {load_module,emqx_cm,brutal_purge,soft_purge,[]},
@@ -209,7 +243,9 @@
      {load_module,emqx_rpc,brutal_purge,soft_purge,[]},
      {load_module,emqx_app,brutal_purge,soft_purge,[]}]},
    {"4.3.6",
-    [{load_module,emqx_http_lib,brutal_purge,soft_purge,[]},
+    [{load_module,emqx_vm,brutal_purge,soft_purge,[]},
+     {load_module,emqx_sys_mon,brutal_purge,soft_purge,[]},
+     {load_module,emqx_http_lib,brutal_purge,soft_purge,[]},
      {load_module,emqx_connection,brutal_purge,soft_purge,[]},
      {load_module,emqx_channel,brutal_purge,soft_purge,[]},
      {load_module,emqx_cm,brutal_purge,soft_purge,[]},
@@ -223,7 +259,9 @@
      {load_module,emqx_rpc,brutal_purge,soft_purge,[]},
      {load_module,emqx_app,brutal_purge,soft_purge,[]}]},
    {"4.3.5",
-    [{load_module,emqx_http_lib,brutal_purge,soft_purge,[]},
+    [{load_module,emqx_vm,brutal_purge,soft_purge,[]},
+     {load_module,emqx_sys_mon,brutal_purge,soft_purge,[]},
+     {load_module,emqx_http_lib,brutal_purge,soft_purge,[]},
      {load_module,emqx_connection,brutal_purge,soft_purge,[]},
      {load_module,emqx_channel,brutal_purge,soft_purge,[]},
      {load_module,emqx_ws_connection,brutal_purge,soft_purge,[]},
@@ -238,7 +276,9 @@
      {load_module,emqx_rpc,brutal_purge,soft_purge,[]},
      {load_module,emqx_app,brutal_purge,soft_purge,[]}]},
    {"4.3.4",
-    [{load_module,emqx_http_lib,brutal_purge,soft_purge,[]},
+    [{load_module,emqx_vm,brutal_purge,soft_purge,[]},
+     {load_module,emqx_sys_mon,brutal_purge,soft_purge,[]},
+     {load_module,emqx_http_lib,brutal_purge,soft_purge,[]},
      {load_module,emqx_connection,brutal_purge,soft_purge,[]},
      {load_module,emqx_channel,brutal_purge,soft_purge,[]},
      {load_module,emqx_ws_connection,brutal_purge,soft_purge,[]},
@@ -254,7 +294,9 @@
      {load_module,emqx_rpc,brutal_purge,soft_purge,[]},
      {load_module,emqx_app,brutal_purge,soft_purge,[]}]},
    {"4.3.3",
-    [{load_module,emqx_http_lib,brutal_purge,soft_purge,[]},
+    [{load_module,emqx_vm,brutal_purge,soft_purge,[]},
+     {load_module,emqx_sys_mon,brutal_purge,soft_purge,[]},
+     {load_module,emqx_http_lib,brutal_purge,soft_purge,[]},
      {load_module,emqx_connection,brutal_purge,soft_purge,[]},
      {load_module,emqx_channel,brutal_purge,soft_purge,[]},
      {load_module,emqx_pqueue,brutal_purge,soft_purge,[]},
@@ -271,7 +313,9 @@
      {load_module,emqx_rpc,brutal_purge,soft_purge,[]},
      {load_module,emqx_app,brutal_purge,soft_purge,[]}]},
    {"4.3.2",
-    [{load_module,emqx_pqueue,brutal_purge,soft_purge,[]},
+    [{load_module,emqx_vm,brutal_purge,soft_purge,[]},
+     {load_module,emqx_sys_mon,brutal_purge,soft_purge,[]},
+     {load_module,emqx_pqueue,brutal_purge,soft_purge,[]},
      {load_module,emqx_mqueue,brutal_purge,soft_purge,[]},
      {load_module,emqx_alarm_handler,brutal_purge,soft_purge,[]},
      {load_module,emqx_misc,brutal_purge,soft_purge,[]},
@@ -288,7 +332,9 @@
      {load_module,emqx_rpc,brutal_purge,soft_purge,[]},
      {load_module,emqx_app,brutal_purge,soft_purge,[]}]},
    {"4.3.1",
-    [{load_module,emqx_pqueue,brutal_purge,soft_purge,[]},
+    [{load_module,emqx_vm,brutal_purge,soft_purge,[]},
+     {load_module,emqx_sys_mon,brutal_purge,soft_purge,[]},
+     {load_module,emqx_pqueue,brutal_purge,soft_purge,[]},
      {load_module,emqx_mqueue,brutal_purge,soft_purge,[]},
      {load_module,emqx_alarm_handler,brutal_purge,soft_purge,[]},
      {load_module,emqx_misc,brutal_purge,soft_purge,[]},
@@ -309,7 +355,9 @@
      {load_module,emqx_rpc,brutal_purge,soft_purge,[]},
      {load_module,emqx_app,brutal_purge,soft_purge,[]}]},
    {"4.3.0",
-    [{load_module,emqx_alarm_handler,brutal_purge,soft_purge,[]},
+    [{load_module,emqx_vm,brutal_purge,soft_purge,[]},
+     {load_module,emqx_sys_mon,brutal_purge,soft_purge,[]},
+     {load_module,emqx_alarm_handler,brutal_purge,soft_purge,[]},
      {load_module,emqx_misc,brutal_purge,soft_purge,[]},
      {load_module,emqx_packet,brutal_purge,soft_purge,[]},
      {load_module,emqx_shared_sub,brutal_purge,soft_purge,[]},
diff --git a/src/emqx_sys_mon.erl b/src/emqx_sys_mon.erl
index 152f975eb..710895bcd 100644
--- a/src/emqx_sys_mon.erl
+++ b/src/emqx_sys_mon.erl
@@ -182,7 +182,15 @@ procinfo(Pid) ->
     case {emqx_vm:get_process_info(Pid), emqx_vm:get_process_gc_info(Pid)} of
         {undefined, _} -> undefined;
         {_, undefined} -> undefined;
-        {Info, GcInfo} -> Info ++ GcInfo
+        {Info, GcInfo} -> get_proc_lib_initial_call(Pid) ++ GcInfo ++ Info
+    end.
+
+get_proc_lib_initial_call(Pid) ->
+    case proc_lib:initial_call(Pid) of
+        false ->
+            [];
+        InitialCall ->
+            [{proc_lib_initial_call, InitialCall}]
     end.
 
 safe_publish(Event, WarnMsg) ->
diff --git a/src/emqx_vm.erl b/src/emqx_vm.erl
index 537330b01..adcbcabb0 100644
--- a/src/emqx_vm.erl
+++ b/src/emqx_vm.erl
@@ -58,11 +58,12 @@
                           sl_alloc,
                           ll_alloc,
                           fix_alloc,
+                          literal_alloc,
                           std_alloc
                          ]).
 
 -define(PROCESS_INFO_KEYS, [initial_call,
-                            current_function,
+                            current_stacktrace,
                             registered_name,
                             status,
                             message_queue_len,
@@ -317,7 +318,8 @@ get_process_gc_info(Pid) when is_pid(Pid) ->
     process_info(Pid, ?PROCESS_GC_KEYS).
 
 get_process_group_leader_info(LeaderPid) when is_pid(LeaderPid) ->
-    [{Key, Value}|| {Key, Value} <- process_info(LeaderPid), lists:member(Key, ?PROCESS_INFO_KEYS)].
+    [{Key, Value}
+     || {Key, Value} <- process_info(LeaderPid), lists:member(Key, ?PROCESS_INFO_KEYS)].
 
 get_process_limit() ->
     erlang:system_info(process_limit).
@@ -339,12 +341,12 @@ get_ets_info(Tab) ->
 mapping(Entries) ->
     mapping(Entries, []).
 mapping([], Acc) -> Acc;
-mapping([{owner, V}|Entries], Acc) when is_pid(V) ->
+mapping([{owner, V} | Entries], Acc) when is_pid(V) ->
     OwnerInfo = process_info(V),
     Owner = proplists:get_value(registered_name, OwnerInfo, undefined),
-    mapping(Entries, [{owner, Owner}|Acc]);
-mapping([{Key, Value}|Entries], Acc) ->
-    mapping(Entries, [{Key, Value}|Acc]).
+    mapping(Entries, [{owner, Owner} | Acc]);
+mapping([{Key, Value} | Entries], Acc) ->
+    mapping(Entries, [{Key, Value} | Acc]).
 
 avg1() ->
     compat_windows(fun cpu_sup:avg1/0).
diff --git a/test/emqx_channel_SUITE.erl b/test/emqx_channel_SUITE.erl
index 60e2541aa..92d191b2a 100644
--- a/test/emqx_channel_SUITE.erl
+++ b/test/emqx_channel_SUITE.erl
@@ -85,7 +85,7 @@ t_chan_caps(_) ->
      #{max_clientid_len := 65535,
        max_qos_allowed := 2,
        max_topic_alias := 65535,
-       max_topic_levels := 0,
+       max_topic_levels := 128,
        retain_available := true,
        shared_subscription := true,
        subscription_identifiers := true,
diff --git a/test/emqx_sys_mon_SUITE.erl b/test/emqx_sys_mon_SUITE.erl
index 70f518ad5..63e7c376a 100644
--- a/test/emqx_sys_mon_SUITE.erl
+++ b/test/emqx_sys_mon_SUITE.erl
@@ -70,23 +70,51 @@ init_per_testcase(t_sys_mon2, Config) ->
            (_) -> ok
         end),
     Config;
+init_per_testcase(t_procinfo, Config) ->
+    emqx_ct_helpers:boot_modules(all),
+    emqx_ct_helpers:start_apps([]),
+    ok = meck:new(emqx_vm, [passthrough, no_history]),
+    Config;
 init_per_testcase(_, Config) ->
     emqx_ct_helpers:boot_modules(all),
     emqx_ct_helpers:start_apps([]),
     Config.
 
+end_per_testcase(t_procinfo, _Config) ->
+    ok = meck:unload(emqx_vm),
+    emqx_ct_helpers:stop_apps([]);
 end_per_testcase(_, _Config) ->
     emqx_ct_helpers:stop_apps([]).
 
 t_procinfo(_) ->
-    ok = meck:new(emqx_vm, [passthrough, no_history]),
     ok = meck:expect(emqx_vm, get_process_info, fun(_) -> [] end),
     ok = meck:expect(emqx_vm, get_process_gc_info, fun(_) -> [] end),
     ?assertEqual([], emqx_sys_mon:procinfo([])),
     ok = meck:expect(emqx_vm, get_process_info, fun(_) -> ok end),
     ok = meck:expect(emqx_vm, get_process_gc_info, fun(_) -> undefined end),
-    ?assertEqual(undefined, emqx_sys_mon:procinfo([])),
-    ok = meck:unload(emqx_vm).
+    ?assertEqual(undefined, emqx_sys_mon:procinfo([])).
+
+t_procinfo_initial_call_and_stacktrace(_) ->
+    SomePid = proc_lib:spawn(?MODULE, some_function, [self(), arg2]),
+    receive
+        {spawned, SomePid} ->
+            ok
+    after 100 ->
+            error(process_not_spawned)
+    end,
+    ProcInfo = emqx_sys_mon:procinfo(SomePid),
+    ?assertEqual(
+       {?MODULE, some_function, ['Argument__1','Argument__2']},
+       proplists:get_value(proc_lib_initial_call, ProcInfo)),
+    ?assertMatch(
+       [{?MODULE, some_function, 2,
+         [{file, _},
+          {line, _}]},
+        {proc_lib, init_p_do_apply, 3,
+         [{file, _},
+          {line, _}]}],
+       proplists:get_value(current_stacktrace, ProcInfo)),
+    SomePid ! stop.
 
 t_sys_mon(_Config) ->
     lists:foreach(
@@ -120,3 +148,10 @@ validate_sys_mon_info(PidOrPort, SysMonName,ValidateInfo, InfoOrPort) ->
 concat_str(ValidateInfo, InfoOrPort, Info) ->
     WarnInfo = io_lib:format(ValidateInfo, [InfoOrPort, Info]),
     lists:flatten(WarnInfo).
+
+some_function(Parent, _Arg2) ->
+    Parent ! {spawned, self()},
+    receive
+        stop ->
+            ok
+    end.