diff --git a/.gitignore b/.gitignore
index 2e19823c3..ded111ff0 100644
--- a/.gitignore
+++ b/.gitignore
@@ -42,3 +42,11 @@ erlang.mk
 etc/emqx.conf.rendered
 Mnesia.*/
 .stamp
+erlang_ls.config
+# Emacs Backup files
+*~
+# Emacs temporary files
+.#*
+*#
+# For direnv
+.envrc
diff --git a/priv/emqx.schema b/priv/emqx.schema
index 0ff956869..10daac600 100644
--- a/priv/emqx.schema
+++ b/priv/emqx.schema
@@ -255,6 +255,27 @@ end}.
 {validator, "range4ports", "must be 1024 to 134217727",
  fun(X) -> X >= 1024 andalso X =< 134217727 end}.
 
+{validator, "range:0-2", "must be 0 to 2",
+ fun(X) -> X >= 0 andalso X =< 2 end}.
+
+{validator, "range:0-128", "must be 0 to 128",
+  fun(X) -> X >= 0 andalso X =< 128 end}.
+
+{validator, "range:0-65535", "must be 0 to 65535",
+ fun(X) -> X >= 0 andalso X =< 65535 end}.
+
+{validator, "range:1-65535", "must be 1 to 65535",
+  fun(X) -> X >= 1 andalso X =< 65535 end}.
+
+{validator, "range:1-9", "must be 1 to 9",
+  fun(X) -> X >= 1 andalso X =< 9 end}.
+
+{validator, "range:8-15", "must be 8 to 15",
+    fun(X) -> X >= 8 andalso X =< 15 end}.
+
+{validator, "range:0-1024", "must be 0 to 1024",
+  fun(X) -> X >= 0 andalso X =< 1024 end}.
+
 %% @doc http://www.erlang.org/doc/man/erl.html#%2bzdbbl
 {mapping, "node.dist_buffer_size", "vm_args.+zdbbl", [
   {datatype, bytesize},
@@ -290,10 +311,10 @@ end}.
   {default, 1000},
   {datatype, integer},
   hidden,
-  {validators, ["positive_integer"]}
+  {validators, ["range:0-inf"]}
 ]}.
 
-{validator, "positive_integer", "must be a positive integer",
+{validator, "range:0-inf", "must be non neg_integer",
   fun(X) -> X >= 0 end}.
 
 %% Note: OTP R15 and earlier uses -env ERL_MAX_ETS_TABLES,
@@ -758,7 +779,8 @@ end}.
 %% @doc Set the Maximum topic levels.
 {mapping, "mqtt.max_topic_levels", "emqx.max_topic_levels", [
   {default, 128},
-  {datatype, integer}
+  {datatype, integer},
+  {validators, ["range:0-inf"]}
 ]}.
 
 %% @doc Set the Maximum QoS allowed.
@@ -771,7 +793,8 @@ end}.
 %% @doc Set the Maximum Topic Alias.
 {mapping, "mqtt.max_topic_alias", "emqx.max_topic_alias", [
   {default, 65535},
-  {datatype, integer}
+  {datatype, integer},
+  {validators, ["range:0-65535"]}
 ]}.
 
 %% @doc Whether the server supports MQTT retained messages.
@@ -868,7 +891,8 @@ end}.
 
 %% @doc Set the Maximum topic levels.
 {mapping, "zone.$name.max_topic_levels", "emqx.zones", [
-  {datatype, integer}
+  {datatype, integer},
+  {validators, ["range:0-128"]}
 ]}.
 
 %% @doc Set the Maximum QoS allowed.
diff --git a/src/emqx.appup.src b/src/emqx.appup.src
index d37dc20c1..dbaeae143 100644
--- a/src/emqx.appup.src
+++ b/src/emqx.appup.src
@@ -3,12 +3,15 @@
 {VSN,
  [
    {"4.2.0", [
+     {load_module, emqx_message, brutal_purge, soft_purge, []},
      {add_module, emqx_congestion},
      {load_module, emqx_alarm, brutal_purge, soft_purge, []},
      {load_module, emqx_channel, brutal_purge, soft_purge, []},
      {load_module, emqx_session, brutal_purge, soft_purge, []},
      {load_module, emqx_metrics, brutal_purge, soft_purge, []},
      {load_module, emqx_limiter, brutal_purge, soft_purge, []},
+     {load_module, emqx_listeners, brutal_purge, soft_purge, []},
+     {load_module, emqx_sys, brutal_purge, soft_purge, []},
      {suspend, [esockd_acceptor,emqx_connection, emqx_ws_connection]},
      {load_module, emqx_frame, brutal_purge, soft_purge, []},
      {update, emqx_connection, {advanced, []}},
@@ -22,17 +25,22 @@
      {load_module, emqx_router, soft_purge, soft_purge, [emqx_trie]},
      {load_module, emqx_cm, brutal_purge, soft_purge, []},
      {load_module, emqx_access_rule, 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,[]}
+     {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_app, brutal_purge, soft_purge, []},
+     {load_module, emqx_misc,brutal_purge,soft_purge,[]},
+     {load_module, emqx_plugins, brutal_purge, soft_purge, []}
    ]},
    {"4.2.1", [
+     {load_module, emqx_message, brutal_purge, soft_purge, []},
      {add_module, emqx_congestion},
      {load_module, emqx_alarm, brutal_purge, soft_purge, []},
      {load_module, emqx_channel, brutal_purge, soft_purge, []},
      {load_module, emqx_session, brutal_purge, soft_purge, []},
      {load_module, emqx_limiter, brutal_purge, soft_purge, []},
+     {load_module, emqx_listeners, brutal_purge, soft_purge, []},
+     {load_module, emqx_sys, brutal_purge, soft_purge, []},
      {suspend, [esockd_acceptor, emqx_connection, emqx_ws_connection]},
      {load_module, emqx_frame, brutal_purge, soft_purge, []},
      {update, emqx_connection, {advanced, []}},
@@ -46,12 +54,15 @@
      {load_module, emqx_router, soft_purge, soft_purge, [emqx_trie]},
      {load_module, emqx_cm, brutal_purge, soft_purge, []},
      {load_module, emqx_access_rule, 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,[]}
+     {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_app, brutal_purge, soft_purge, []},
+     {load_module, emqx_misc,brutal_purge,soft_purge,[]},
+     {load_module, emqx_plugins, brutal_purge, soft_purge, []}
    ]},
    {<<"4.2.[23]">>, [
+     {load_module, emqx_message, brutal_purge, soft_purge, []},
      {add_module, emqx_congestion},
      {load_module, emqx_frame, brutal_purge, soft_purge, []},
      {load_module, emqx_alarm, brutal_purge, soft_purge, []},
@@ -67,19 +78,25 @@
      {load_module, emqx_router, soft_purge, soft_purge, [emqx_trie]},
      {load_module, emqx_cm, brutal_purge, soft_purge, []},
      {load_module, emqx_access_rule, 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,[]},
-     {load_module, emqx_limiter, 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,[]},
+     {load_module, emqx_app, brutal_purge, soft_purge, []},
+     {load_module, emqx_limiter, brutal_purge, soft_purge, []},
+     {load_module, emqx_listeners, brutal_purge, soft_purge, []},
+     {load_module, emqx_sys, brutal_purge, soft_purge, []},
+     {load_module, emqx_plugins, brutal_purge, soft_purge, []}
    ]},
    {<<"4.2.4">>, [
+     {load_module, emqx_message, brutal_purge, soft_purge, []},
      {load_module, emqx_frame, brutal_purge, soft_purge, []},
      {load_module, emqx_channel, brutal_purge, soft_purge, []},
      {load_module, emqx_session, brutal_purge, soft_purge, []},
      {load_module, emqx_congestion, brutal_purge, soft_purge, []},
      {update, emqx_connection, {advanced, []}},
      {load_module, emqx_ws_connection, brutal_purge, soft_purge, []},
+     {load_module, emqx_os_mon, brutal_purge, soft_purge, []},
      {load_module, emqx_alarm, brutal_purge, soft_purge, []},
      {load_module, emqx_router_sup, soft_purge, soft_purge, []},
      {load_module, emqx_broker, soft_purge, soft_purge, []},
@@ -87,19 +104,25 @@
      {load_module, emqx_router, soft_purge, soft_purge, [emqx_trie]},
      {load_module, emqx_cm, brutal_purge, soft_purge, []},
      {load_module, emqx_access_rule, 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,[]},
-     {load_module, emqx_limiter, 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,[]},
+     {load_module, emqx_app, brutal_purge, soft_purge, []},
+     {load_module, emqx_limiter, brutal_purge, soft_purge, []},
+     {load_module, emqx_listeners, brutal_purge, soft_purge, []},
+     {load_module, emqx_sys, brutal_purge, soft_purge, []},
+     {load_module, emqx_plugins, brutal_purge, soft_purge, []}
    ]},
    {<<"4.2.5">>, [
+     {load_module, emqx_message, brutal_purge, soft_purge, []},
      {load_module, emqx_frame, brutal_purge, soft_purge, []},
      {load_module, emqx_channel, brutal_purge, soft_purge, []},
      {load_module, emqx_session, brutal_purge, soft_purge, []},
      {load_module, emqx_congestion, brutal_purge, soft_purge, []},
      {update, emqx_connection, {advanced, []}},
      {load_module, emqx_ws_connection, brutal_purge, soft_purge, []},
+     {load_module, emqx_os_mon, brutal_purge, soft_purge, []},
      {load_module, emqx_alarm, brutal_purge, soft_purge, []},
      {load_module, emqx_router_sup, soft_purge, soft_purge, []},
      {load_module, emqx_broker, soft_purge, soft_purge, []},
@@ -107,48 +130,88 @@
      {load_module, emqx_router, soft_purge, soft_purge, [emqx_trie]},
      {load_module, emqx_cm, brutal_purge, soft_purge, []},
      {load_module, emqx_access_rule, 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,[]},
-     {load_module, emqx_limiter, 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,[]},
+     {load_module, emqx_app, brutal_purge, soft_purge, []},
+     {load_module, emqx_limiter, brutal_purge, soft_purge, []},
+     {load_module, emqx_listeners, brutal_purge, soft_purge, []},
+     {load_module, emqx_plugins, brutal_purge, soft_purge, []}
    ]},
    {<<"4.2.[6-7]">>, [
+     {load_module, emqx_message, brutal_purge, soft_purge, []},
      {load_module, emqx_frame, brutal_purge, soft_purge, []},
      {load_module, emqx_channel, brutal_purge, soft_purge, []},
      {load_module, emqx_connection, brutal_purge, soft_purge, []},
      {load_module, emqx_ws_connection, brutal_purge, soft_purge, []},
      {load_module, emqx_cm, brutal_purge, soft_purge, []},
      {load_module, emqx_access_rule, 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,[]},
-     {load_module, emqx_limiter, 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,[]},
+     {load_module, emqx_app, brutal_purge, soft_purge, []},
+     {load_module, emqx_alarm, brutal_purge, soft_purge, []},
+     {load_module, emqx_os_mon, brutal_purge, soft_purge, []},
+     {load_module, emqx_limiter, brutal_purge, soft_purge, []},
+     {load_module, emqx_listeners, brutal_purge, soft_purge, []},
+     {load_module, emqx_sys, brutal_purge, soft_purge, []},
+     {load_module, emqx_plugins, brutal_purge, soft_purge, []}
    ]},
    {<<"4.2.8">>, [
+     {load_module, emqx_message, brutal_purge, soft_purge, []},
      {load_module, emqx_frame, brutal_purge, soft_purge, []},
      {load_module, emqx_channel, brutal_purge, soft_purge, []},
      {load_module, emqx_connection, brutal_purge, soft_purge, []},
      {load_module, emqx_ws_connection, brutal_purge, soft_purge, []},
      {load_module, emqx_cm, brutal_purge, soft_purge, []},
-     {load_module, emqx_limiter, brutal_purge, soft_purge, []}
+     {load_module, emqx_limiter, brutal_purge, soft_purge, []},
+     {load_module, emqx_listeners, brutal_purge, soft_purge, []},
+     {load_module, emqx_sys, brutal_purge, soft_purge, []},
+     {load_module, emqx_app, brutal_purge, soft_purge, []},
+     {load_module, emqx_alarm, brutal_purge, soft_purge, []},
+     {load_module, emqx_os_mon, brutal_purge, soft_purge, []},
+     {load_module, emqx_plugins, brutal_purge, soft_purge, []}
    ]},
    {<<"4.2.9">>, [
+     {load_module, emqx_message, brutal_purge, soft_purge, []},
      {load_module, emqx_frame, brutal_purge, soft_purge, []},
+     {load_module, emqx_channel, brutal_purge, soft_purge, []},
      {load_module, emqx_connection, brutal_purge, soft_purge, []},
      {load_module, emqx_ws_connection, brutal_purge, soft_purge, []},
-     {load_module, emqx_limiter, brutal_purge, soft_purge, []}
+     {load_module, emqx_limiter, brutal_purge, soft_purge, []},
+     {load_module, emqx_listeners, brutal_purge, soft_purge, []},
+     {load_module, emqx_sys, brutal_purge, soft_purge, []},
+     {load_module, emqx_app, brutal_purge, soft_purge, []},
+     {load_module, emqx_alarm, brutal_purge, soft_purge, []},
+     {load_module, emqx_os_mon, brutal_purge, soft_purge, []},
+     {load_module, emqx_plugins, brutal_purge, soft_purge, []}
+   ]},
+   {<<"4.2.10">>, [
+     {load_module, emqx_message, brutal_purge, soft_purge, []},
+     {load_module, emqx_channel, brutal_purge, soft_purge, []},
+     {load_module, emqx_frame, brutal_purge, soft_purge, []},
+     {load_module, emqx_app, brutal_purge, soft_purge, []},
+     {load_module, emqx_os_mon, brutal_purge, soft_purge, []},
+     {load_module, emqx_alarm, brutal_purge, soft_purge, []},
+     {load_module, emqx_limiter, brutal_purge, soft_purge, []},
+     {load_module, emqx_listeners, brutal_purge, soft_purge, []},
+     {load_module, emqx_sys, brutal_purge, soft_purge, []},
+     {load_module, emqx_plugins, brutal_purge, soft_purge, []}
    ]},
    {<<".*">>, []}
  ],
  [
    {"4.2.0", [
+     {load_module, emqx_message, brutal_purge, soft_purge, []},
      {load_module, emqx_shared_sub, brutal_purge, soft_purge, []},
      {load_module, emqx_os_mon, brutal_purge, soft_purge, []},
      {load_module, emqx_alarm, brutal_purge, soft_purge, []},
      {load_module, emqx_metrics, brutal_purge, soft_purge, []},
      {load_module, emqx_limiter, brutal_purge, soft_purge, []},
+     {load_module, emqx_listeners, brutal_purge, soft_purge, []},
+     {load_module, emqx_sys, brutal_purge, soft_purge, []},
      {suspend, [esockd_acceptor, emqx_connection, emqx_ws_connection]},
      {load_module, emqx_frame, brutal_purge, soft_purge, []},
      {update, emqx_connection, {advanced, []}},
@@ -163,15 +226,20 @@
      {load_module, emqx_router, soft_purge, soft_purge, []},
      {load_module, emqx_cm, brutal_purge, soft_purge, []},
      {load_module, emqx_access_rule, 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,[]}
+     {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_app, brutal_purge, soft_purge, []},
+     {load_module, emqx_misc,brutal_purge,soft_purge,[]},
+     {load_module, emqx_plugins, brutal_purge, soft_purge, []}
    ]},
    {"4.2.1", [
+     {load_module, emqx_message, brutal_purge, soft_purge, []},
      {load_module, emqx_shared_sub, brutal_purge, soft_purge, []},
      {load_module, emqx_os_mon, brutal_purge, soft_purge, []},
      {load_module, emqx_limiter, brutal_purge, soft_purge, []},
+     {load_module, emqx_listeners, brutal_purge, soft_purge, []},
+     {load_module, emqx_sys, brutal_purge, soft_purge, []},
      {suspend, [esockd_acceptor, emqx_connection, emqx_ws_connection]},
      {load_module, emqx_channel, brutal_purge, soft_purge, []},
      {load_module, emqx_session, brutal_purge, soft_purge, []},
@@ -187,12 +255,15 @@
      {load_module, emqx_router, soft_purge, soft_purge, []},
      {load_module, emqx_cm, brutal_purge, soft_purge, []},
      {load_module, emqx_access_rule, 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,[]}
+     {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_app, brutal_purge, soft_purge, []},
+     {load_module, emqx_misc,brutal_purge,soft_purge,[]},
+     {load_module, emqx_plugins, brutal_purge, soft_purge, []}
    ]},
    {<<"4.2.[23]">>, [
+     {load_module, emqx_message, brutal_purge, soft_purge, []},
      {load_module, emqx_shared_sub, brutal_purge, soft_purge, []},
      {load_module, emqx_os_mon, brutal_purge, soft_purge, []},
      {update, emqx_connection, {advanced, []}},
@@ -208,13 +279,18 @@
      {load_module, emqx_router, soft_purge, soft_purge, []},
      {load_module, emqx_cm, brutal_purge, soft_purge, []},
      {load_module, emqx_access_rule, 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,[]},
-     {load_module, emqx_limiter, 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,[]},
+     {load_module, emqx_app, brutal_purge, soft_purge, []},
+     {load_module, emqx_limiter, brutal_purge, soft_purge, []},
+     {load_module, emqx_listeners, brutal_purge, soft_purge, []},
+     {load_module, emqx_sys, brutal_purge, soft_purge, []},
+     {load_module, emqx_plugins, brutal_purge, soft_purge, []}
    ]},
    {<<"4.2.4">>, [
+     {load_module, emqx_message, brutal_purge, soft_purge, []},
      {load_module, emqx_frame, brutal_purge, soft_purge, []},
      {load_module, emqx_channel, brutal_purge, soft_purge, []},
      {load_module, emqx_congestion, brutal_purge, soft_purge, []},
@@ -228,13 +304,19 @@
      {load_module, emqx_router, soft_purge, soft_purge, []},
      {load_module, emqx_cm, brutal_purge, soft_purge, []},
      {load_module, emqx_access_rule, 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,[]},
-     {load_module, emqx_limiter, 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_app, brutal_purge, soft_purge, []},
+     {load_module, emqx_os_mon, brutal_purge, soft_purge, []},
+     {load_module, emqx_misc,brutal_purge,soft_purge,[]},
+     {load_module, emqx_limiter, brutal_purge, soft_purge, []},
+     {load_module, emqx_listeners, brutal_purge, soft_purge, []},
+     {load_module, emqx_sys, brutal_purge, soft_purge, []},
+     {load_module, emqx_plugins, brutal_purge, soft_purge, []}
    ]},
    {<<"4.2.5">>, [
+     {load_module, emqx_message, brutal_purge, soft_purge, []},
      {load_module, emqx_frame, brutal_purge, soft_purge, []},
      {load_module, emqx_channel, brutal_purge, soft_purge, []},
      {load_module, emqx_session, brutal_purge, soft_purge, []},
@@ -248,38 +330,77 @@
      {load_module, emqx_router, soft_purge, soft_purge, []},
      {load_module, emqx_cm, brutal_purge, soft_purge, []},
      {load_module, emqx_access_rule, 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,[]},
-     {load_module, emqx_limiter, 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_app, brutal_purge, soft_purge, []},
+     {load_module, emqx_os_mon, brutal_purge, soft_purge, []},
+     {load_module, emqx_misc,brutal_purge,soft_purge,[]},
+     {load_module, emqx_limiter, brutal_purge, soft_purge, []},
+     {load_module, emqx_listeners, brutal_purge, soft_purge, []},
+     {load_module, emqx_sys, brutal_purge, soft_purge, []},
+     {load_module, emqx_plugins, brutal_purge, soft_purge, []}
    ]},
    {<<"4.2.[6-7]">>, [
+     {load_module, emqx_message, brutal_purge, soft_purge, []},
      {load_module, emqx_frame, brutal_purge, soft_purge, []},
      {load_module, emqx_channel, brutal_purge, soft_purge, []},
      {load_module, emqx_connection, brutal_purge, soft_purge, []},
      {load_module, emqx_ws_connection, brutal_purge, soft_purge, []},
      {load_module, emqx_cm, brutal_purge, soft_purge, []},
      {load_module, emqx_access_rule, 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,[]},
-     {load_module, emqx_limiter, 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_app, brutal_purge, soft_purge, []},
+     {load_module, emqx_os_mon, brutal_purge, soft_purge, []},
+     {load_module, emqx_alarm, brutal_purge, soft_purge, []},
+     {load_module, emqx_misc,brutal_purge,soft_purge,[]},
+     {load_module, emqx_limiter, brutal_purge, soft_purge, []},
+     {load_module, emqx_listeners, brutal_purge, soft_purge, []},
+     {load_module, emqx_sys, brutal_purge, soft_purge, []},
+     {load_module, emqx_plugins, brutal_purge, soft_purge, []}
    ]},
    {<<"4.2.8">>, [
+     {load_module, emqx_message, brutal_purge, soft_purge, []},
      {load_module, emqx_frame, brutal_purge, soft_purge, []},
      {load_module, emqx_channel, brutal_purge, soft_purge, []},
      {load_module, emqx_connection, brutal_purge, soft_purge, []},
      {load_module, emqx_ws_connection, brutal_purge, soft_purge, []},
      {load_module, emqx_cm, brutal_purge, soft_purge, []},
-     {load_module, emqx_limiter, brutal_purge, soft_purge, []}
+     {load_module, emqx_app, brutal_purge, soft_purge, []},
+     {load_module, emqx_os_mon, brutal_purge, soft_purge, []},
+     {load_module, emqx_alarm, brutal_purge, soft_purge, []},
+     {load_module, emqx_limiter, brutal_purge, soft_purge, []},
+     {load_module, emqx_listeners, brutal_purge, soft_purge, []},
+     {load_module, emqx_sys, brutal_purge, soft_purge, []},
+     {load_module, emqx_plugins, brutal_purge, soft_purge, []}
    ]},
    {<<"4.2.9">>, [
+     {load_module, emqx_message, brutal_purge, soft_purge, []},
      {load_module, emqx_frame, brutal_purge, soft_purge, []},
+     {load_module, emqx_channel, brutal_purge, soft_purge, []},
      {load_module, emqx_connection, brutal_purge, soft_purge, []},
      {load_module, emqx_ws_connection, brutal_purge, soft_purge, []},
-     {load_module, emqx_limiter, brutal_purge, soft_purge, []}
+     {load_module, emqx_limiter, brutal_purge, soft_purge, []},
+     {load_module, emqx_listeners, brutal_purge, soft_purge, []},
+     {load_module, emqx_sys, brutal_purge, soft_purge, []},
+     {load_module, emqx_app, brutal_purge, soft_purge, []},
+     {load_module, emqx_os_mon, brutal_purge, soft_purge, []},
+     {load_module, emqx_alarm, brutal_purge, soft_purge, []},
+     {load_module, emqx_plugins, brutal_purge, soft_purge, []}
+   ]},
+   {<<"4.2.10">>, [
+     {load_module, emqx_message, brutal_purge, soft_purge, []},
+     {load_module, emqx_channel, brutal_purge, soft_purge, []},
+     {load_module, emqx_frame, brutal_purge, soft_purge, []},
+     {load_module, emqx_app, brutal_purge, soft_purge, []},
+     {load_module, emqx_os_mon, brutal_purge, soft_purge, []},
+     {load_module, emqx_alarm, brutal_purge, soft_purge, []},
+     {load_module, emqx_limiter, brutal_purge, soft_purge, []},
+     {load_module, emqx_listeners, brutal_purge, soft_purge, []},
+     {load_module, emqx_sys, brutal_purge, soft_purge, []},
+     {load_module, emqx_plugins, brutal_purge, soft_purge, []}
    ]},
    {<<".*">>, []}
  ]
diff --git a/src/emqx_alarm.erl b/src/emqx_alarm.erl
index ced6622bf..d07354105 100644
--- a/src/emqx_alarm.erl
+++ b/src/emqx_alarm.erl
@@ -56,9 +56,9 @@
           name :: binary() | atom(),
 
           details :: map() | list(),
-    
+
           message :: binary(),
-    
+
           activate_at :: integer()
         }).
 
@@ -68,9 +68,9 @@
           name :: binary() | atom(),
 
           details :: map() | list(),
-    
+
           message :: binary(),
-    
+
           deactivate_at :: integer() | infinity
         }).
 
@@ -165,6 +165,8 @@ init([Opts]) ->
     Actions = proplists:get_value(actions, Opts),
     SizeLimit = proplists:get_value(size_limit, Opts),
     ValidityPeriod = timer:seconds(proplists:get_value(validity_period, Opts)),
+    emqx_alarm_handler:load(),
+    process_flag(trap_exit, true),
     {ok, ensure_delete_timer(#state{actions = Actions,
                                     size_limit = SizeLimit,
                                     validity_period = ValidityPeriod})}.
@@ -228,6 +230,7 @@ handle_info(Info, State) ->
     {noreply, State}.
 
 terminate(_Reason, _State) ->
+    emqx_alarm_handler:unload(),
     ok.
 
 code_change(_OldVsn, State, _Extra) ->
diff --git a/src/emqx_app.erl b/src/emqx_app.erl
index 881a1ee99..077b9c889 100644
--- a/src/emqx_app.erl
+++ b/src/emqx_app.erl
@@ -38,13 +38,11 @@ start(_Type, _Args) ->
     ok = emqx_plugins:init(),
     emqx_plugins:load(),
     register(emqx, self()),
-    emqx_alarm_handler:load(),
     print_vsn(),
     {ok, Sup}.
 
 -spec(stop(State :: term()) -> term()).
 stop(_State) ->
-    emqx_alarm_handler:unload(),
     emqx_boot:is_enabled(listeners)
       andalso emqx_listeners:stop().
 
@@ -68,4 +66,3 @@ start_autocluster() ->
     ekka:callback(prepare, fun emqx:shutdown/1),
     ekka:callback(reboot,  fun emqx:reboot/0),
     ekka:autocluster(?APP).
-
diff --git a/src/emqx_channel.erl b/src/emqx_channel.erl
index 1b20753aa..6c03a1a04 100644
--- a/src/emqx_channel.erl
+++ b/src/emqx_channel.erl
@@ -1455,11 +1455,13 @@ enrich_connack_caps(AckProps, _Channel) -> AckProps.
 %%--------------------------------------------------------------------
 %% Enrich server keepalive
 
-enrich_server_keepalive(AckProps, #channel{clientinfo = #{zone := Zone}}) ->
+enrich_server_keepalive(AckProps, ?IS_MQTT_V5 = #channel{clientinfo = #{zone := Zone}}) ->
     case emqx_zone:server_keepalive(Zone) of
         undefined -> AckProps;
         Keepalive -> AckProps#{'Server-Keep-Alive' => Keepalive}
-    end.
+    end;
+
+enrich_server_keepalive(AckProps, _Channel) -> AckProps.
 
 %%--------------------------------------------------------------------
 %% Enrich response information
@@ -1505,7 +1507,7 @@ init_alias_maximum(#mqtt_packet_connect{proto_ver  = ?MQTT_PROTO_V5,
 init_alias_maximum(_ConnPkt, _ClientInfo) -> undefined.
 
 %%--------------------------------------------------------------------
-%% Enrich Keepalive
+%% Ensure Keepalive
 
 ensure_keepalive(#{'Server-Keep-Alive' := Interval}, Channel) ->
     ensure_keepalive_timer(Interval, Channel);
@@ -1671,4 +1673,3 @@ flag(false) -> 0.
 set_field(Name, Value, Channel) ->
     Pos = emqx_misc:index_of(Name, record_info(fields, channel)),
     setelement(Pos+1, Channel, Value).
-
diff --git a/src/emqx_frame.erl b/src/emqx_frame.erl
index f0e2f6e4e..8dd657253 100644
--- a/src/emqx_frame.erl
+++ b/src/emqx_frame.erl
@@ -78,6 +78,10 @@
 
 -dialyzer({no_match, [serialize_utf8_string/2]}).
 
+-ifdef(TEST).
+-export([parse_variable_byte_integer/1]).
+-endif.
+
 %%--------------------------------------------------------------------
 %% Init Parse State
 %%--------------------------------------------------------------------
@@ -196,8 +200,9 @@ packet(Header, Variable) ->
 packet(Header, Variable, Payload) ->
     #mqtt_packet{header = Header, variable = Variable, payload = Payload}.
 
-parse_packet(#mqtt_packet_header{type = ?CONNECT}, FrameBin, _Options) ->
-    {ProtoName, Rest} = parse_utf8_string(FrameBin),
+parse_packet(#mqtt_packet_header{type = ?CONNECT}, FrameBin,
+             #{strict_mode := StrictMode}) ->
+    {ProtoName, Rest} = parse_utf8_string(FrameBin, StrictMode),
     <<BridgeTag:4, ProtoVer:4, Rest1/binary>> = Rest,
     % Note: Crash when reserved flag doesn't equal to 0, there is no strict
     % compliance with the MQTT5.0.
@@ -211,8 +216,8 @@ parse_packet(#mqtt_packet_header{type = ?CONNECT}, FrameBin, _Options) ->
       KeepAlive    : 16/big,
       Rest2/binary>> = Rest1,
 
-    {Properties, Rest3} = parse_properties(Rest2, ProtoVer),
-    {ClientId, Rest4} = parse_utf8_string(Rest3),
+    {Properties, Rest3} = parse_properties(Rest2, ProtoVer, StrictMode),
+    {ClientId, Rest4} = parse_utf8_string(Rest3, StrictMode),
     ConnPacket = #mqtt_packet_connect{proto_name  = ProtoName,
                                       proto_ver   = ProtoVer,
                                       is_bridge   = (BridgeTag =:= 8),
@@ -224,14 +229,14 @@ parse_packet(#mqtt_packet_header{type = ?CONNECT}, FrameBin, _Options) ->
                                       properties  = Properties,
                                       clientid    = ClientId
                                      },
-    {ConnPacket1, Rest5} = parse_will_message(ConnPacket, Rest4),
-    {Username, Rest6} = parse_utf8_string(Rest5, bool(UsernameFlag)),
-    {Passsword, <<>>} = parse_utf8_string(Rest6, bool(PasswordFlag)),
+    {ConnPacket1, Rest5} = parse_will_message(ConnPacket, Rest4, StrictMode),
+    {Username, Rest6} = parse_utf8_string(Rest5, StrictMode, bool(UsernameFlag)),
+    {Passsword, <<>>} = parse_utf8_string(Rest6, StrictMode, bool(PasswordFlag)),
     ConnPacket1#mqtt_packet_connect{username = Username, password = Passsword};
 
-parse_packet(#mqtt_packet_header{type = ?CONNACK},
-             <<AckFlags:8, ReasonCode:8, Rest/binary>>, #{version := Ver}) ->
-    {Properties, <<>>} = parse_properties(Rest, Ver),
+parse_packet(#mqtt_packet_header{type = ?CONNACK}, <<AckFlags:8, ReasonCode:8, Rest/binary>>,
+             #{strict_mode := StrictMode, version := Ver}) ->
+    {Properties, <<>>} = parse_properties(Rest, Ver, StrictMode),
     #mqtt_packet_connack{ack_flags   = AckFlags,
                          reason_code = ReasonCode,
                          properties  = Properties
@@ -239,21 +244,23 @@ parse_packet(#mqtt_packet_header{type = ?CONNACK},
 
 parse_packet(#mqtt_packet_header{type = ?PUBLISH, qos = QoS}, Bin,
              #{strict_mode := StrictMode, version := Ver}) ->
-    {TopicName, Rest} = parse_utf8_string(Bin),
+    {TopicName, Rest} = parse_utf8_string(Bin, StrictMode),
     {PacketId, Rest1} = case QoS of
                             ?QOS_0 -> {undefined, Rest};
                             _ -> parse_packet_id(Rest)
                         end,
     (PacketId =/= undefined) andalso
       StrictMode andalso validate_packet_id(PacketId),
-    {Properties, Payload} = parse_properties(Rest1, Ver),
+    {Properties, Payload} = parse_properties(Rest1, Ver, StrictMode),
+    ok = ensure_topic_name_valid(StrictMode, TopicName, Properties),
     Publish = #mqtt_packet_publish{topic_name = TopicName,
                                    packet_id  = PacketId,
                                    properties = Properties
                                   },
     {Publish, Payload};
 
-parse_packet(#mqtt_packet_header{type = PubAck}, <<PacketId:16/big>>, #{strict_mode := StrictMode})
+parse_packet(#mqtt_packet_header{type = PubAck}, <<PacketId:16/big>>,
+             #{strict_mode := StrictMode})
   when ?PUBACK =< PubAck, PubAck =< ?PUBCOMP ->
     StrictMode andalso validate_packet_id(PacketId),
     #mqtt_packet_puback{packet_id = PacketId, reason_code = 0};
@@ -262,7 +269,7 @@ parse_packet(#mqtt_packet_header{type = PubAck}, <<PacketId:16/big, ReasonCode,
              #{strict_mode := StrictMode, version := Ver = ?MQTT_PROTO_V5})
   when ?PUBACK =< PubAck, PubAck =< ?PUBCOMP ->
     StrictMode andalso validate_packet_id(PacketId),
-    {Properties, <<>>} = parse_properties(Rest, Ver),
+    {Properties, <<>>} = parse_properties(Rest, Ver, StrictMode),
     #mqtt_packet_puback{packet_id   = PacketId,
                         reason_code = ReasonCode,
                         properties  = Properties
@@ -271,7 +278,7 @@ parse_packet(#mqtt_packet_header{type = PubAck}, <<PacketId:16/big, ReasonCode,
 parse_packet(#mqtt_packet_header{type = ?SUBSCRIBE}, <<PacketId:16/big, Rest/binary>>,
              #{strict_mode := StrictMode, version := Ver}) ->
     StrictMode andalso validate_packet_id(PacketId),
-    {Properties, Rest1} = parse_properties(Rest, Ver),
+    {Properties, Rest1} = parse_properties(Rest, Ver, StrictMode),
     TopicFilters = parse_topic_filters(subscribe, Rest1),
     ok = validate_subqos([QoS || {_, #{qos := QoS}} <- TopicFilters]),
     #mqtt_packet_subscribe{packet_id     = PacketId,
@@ -282,7 +289,7 @@ parse_packet(#mqtt_packet_header{type = ?SUBSCRIBE}, <<PacketId:16/big, Rest/bin
 parse_packet(#mqtt_packet_header{type = ?SUBACK}, <<PacketId:16/big, Rest/binary>>,
              #{strict_mode := StrictMode, version := Ver}) ->
     StrictMode andalso validate_packet_id(PacketId),
-    {Properties, Rest1} = parse_properties(Rest, Ver),
+    {Properties, Rest1} = parse_properties(Rest, Ver, StrictMode),
     ReasonCodes = parse_reason_codes(Rest1),
     #mqtt_packet_suback{packet_id    = PacketId,
                         properties   = Properties,
@@ -292,7 +299,7 @@ parse_packet(#mqtt_packet_header{type = ?SUBACK}, <<PacketId:16/big, Rest/binary
 parse_packet(#mqtt_packet_header{type = ?UNSUBSCRIBE}, <<PacketId:16/big, Rest/binary>>,
              #{strict_mode := StrictMode, version := Ver}) ->
     StrictMode andalso validate_packet_id(PacketId),
-    {Properties, Rest1} = parse_properties(Rest, Ver),
+    {Properties, Rest1} = parse_properties(Rest, Ver, StrictMode),
     TopicFilters = parse_topic_filters(unsubscribe, Rest1),
     #mqtt_packet_unsubscribe{packet_id     = PacketId,
                              properties    = Properties,
@@ -307,7 +314,7 @@ parse_packet(#mqtt_packet_header{type = ?UNSUBACK}, <<PacketId:16/big>>,
 parse_packet(#mqtt_packet_header{type = ?UNSUBACK}, <<PacketId:16/big, Rest/binary>>,
              #{strict_mode := StrictMode, version := Ver}) ->
     StrictMode andalso validate_packet_id(PacketId),
-    {Properties, Rest1} = parse_properties(Rest, Ver),
+    {Properties, Rest1} = parse_properties(Rest, Ver, StrictMode),
     ReasonCodes = parse_reason_codes(Rest1),
     #mqtt_packet_unsuback{packet_id    = PacketId,
                           properties   = Properties,
@@ -315,115 +322,120 @@ parse_packet(#mqtt_packet_header{type = ?UNSUBACK}, <<PacketId:16/big, Rest/bina
                          };
 
 parse_packet(#mqtt_packet_header{type = ?DISCONNECT}, <<ReasonCode, Rest/binary>>,
-             #{version := ?MQTT_PROTO_V5}) ->
-    {Properties, <<>>} = parse_properties(Rest, ?MQTT_PROTO_V5),
+             #{strict_mode := StrictMode, version := ?MQTT_PROTO_V5}) ->
+    {Properties, <<>>} = parse_properties(Rest, ?MQTT_PROTO_V5, StrictMode),
     #mqtt_packet_disconnect{reason_code = ReasonCode,
                             properties  = Properties
                            };
 
 parse_packet(#mqtt_packet_header{type = ?AUTH}, <<ReasonCode, Rest/binary>>,
-             #{version := ?MQTT_PROTO_V5}) ->
-    {Properties, <<>>} = parse_properties(Rest, ?MQTT_PROTO_V5),
+             #{strict_mode := StrictMode, version := ?MQTT_PROTO_V5}) ->
+    {Properties, <<>>} = parse_properties(Rest, ?MQTT_PROTO_V5, StrictMode),
     #mqtt_packet_auth{reason_code = ReasonCode, properties = Properties}.
 
 parse_will_message(Packet = #mqtt_packet_connect{will_flag = true,
-                                                 proto_ver = Ver}, Bin) ->
-    {Props, Rest} = parse_properties(Bin, Ver),
-    {Topic, Rest1} = parse_utf8_string(Rest),
+                                                 proto_ver = Ver},
+                   Bin, StrictMode) ->
+    {Props, Rest} = parse_properties(Bin, Ver, StrictMode),
+    {Topic, Rest1} = parse_utf8_string(Rest, StrictMode),
     {Payload, Rest2} = parse_binary_data(Rest1),
+    ok = ensure_topic_name_valid(StrictMode, Topic, Props),
     {Packet#mqtt_packet_connect{will_props   = Props,
                                 will_topic   = Topic,
                                 will_payload = Payload
                                }, Rest2};
-parse_will_message(Packet, Bin) -> {Packet, Bin}.
+parse_will_message(Packet, Bin, _StrictMode) -> {Packet, Bin}.
 
 -compile({inline, [parse_packet_id/1]}).
 parse_packet_id(<<PacketId:16/big, Rest/binary>>) ->
     {PacketId, Rest}.
 
-parse_properties(Bin, Ver) when Ver =/= ?MQTT_PROTO_V5 ->
+parse_properties(Bin, Ver, _StrictMode) when Ver =/= ?MQTT_PROTO_V5 ->
     {#{}, Bin};
 %% TODO: version mess?
-parse_properties(<<>>, ?MQTT_PROTO_V5) ->
+parse_properties(<<>>, ?MQTT_PROTO_V5, _StrictMode) ->
     {#{}, <<>>};
-parse_properties(<<0, Rest/binary>>, ?MQTT_PROTO_V5) ->
+parse_properties(<<0, Rest/binary>>, ?MQTT_PROTO_V5, _StrictMode) ->
     {#{}, Rest};
-parse_properties(Bin, ?MQTT_PROTO_V5) ->
+parse_properties(Bin, ?MQTT_PROTO_V5, StrictMode) ->
     {Len, Rest} = parse_variable_byte_integer(Bin),
     <<PropsBin:Len/binary, Rest1/binary>> = Rest,
-    {parse_property(PropsBin, #{}), Rest1}.
+    {parse_property(PropsBin, #{}, StrictMode), Rest1}.
 
-parse_property(<<>>, Props) ->
+parse_property(<<>>, Props, _StrictMode) ->
     Props;
-parse_property(<<16#01, Val, Bin/binary>>, Props) ->
-    parse_property(Bin, Props#{'Payload-Format-Indicator' => Val});
-parse_property(<<16#02, Val:32/big, Bin/binary>>, Props) ->
-    parse_property(Bin, Props#{'Message-Expiry-Interval' => Val});
-parse_property(<<16#03, Bin/binary>>, Props) ->
-    {Val, Rest} = parse_utf8_string(Bin),
-    parse_property(Rest, Props#{'Content-Type' => Val});
-parse_property(<<16#08, Bin/binary>>, Props) ->
-    {Val, Rest} = parse_utf8_string(Bin),
-    parse_property(Rest, Props#{'Response-Topic' => Val});
-parse_property(<<16#09, Len:16/big, Val:Len/binary, Bin/binary>>, Props) ->
-    parse_property(Bin, Props#{'Correlation-Data' => Val});
-parse_property(<<16#0B, Bin/binary>>, Props) ->
+parse_property(<<16#01, Val, Bin/binary>>, Props, StrictMode) ->
+    parse_property(Bin, Props#{'Payload-Format-Indicator' => Val}, StrictMode);
+parse_property(<<16#02, Val:32/big, Bin/binary>>, Props, StrictMode) ->
+    parse_property(Bin, Props#{'Message-Expiry-Interval' => Val}, StrictMode);
+parse_property(<<16#03, Bin/binary>>, Props, StrictMode) ->
+    {Val, Rest} = parse_utf8_string(Bin, StrictMode),
+    parse_property(Rest, Props#{'Content-Type' => Val}, StrictMode);
+parse_property(<<16#08, Bin/binary>>, Props, StrictMode) ->
+    {Val, Rest} = parse_utf8_string(Bin, StrictMode),
+    parse_property(Rest, Props#{'Response-Topic' => Val}, StrictMode);
+parse_property(<<16#09, Len:16/big, Val:Len/binary, Bin/binary>>, Props, StrictMode) ->
+    parse_property(Bin, Props#{'Correlation-Data' => Val}, StrictMode);
+parse_property(<<16#0B, Bin/binary>>, Props, StrictMode) ->
     {Val, Rest} = parse_variable_byte_integer(Bin),
-    parse_property(Rest, Props#{'Subscription-Identifier' => Val});
-parse_property(<<16#11, Val:32/big, Bin/binary>>, Props) ->
-    parse_property(Bin, Props#{'Session-Expiry-Interval' => Val});
-parse_property(<<16#12, Bin/binary>>, Props) ->
-    {Val, Rest} = parse_utf8_string(Bin),
-    parse_property(Rest, Props#{'Assigned-Client-Identifier' => Val});
-parse_property(<<16#13, Val:16, Bin/binary>>, Props) ->
-    parse_property(Bin, Props#{'Server-Keep-Alive' => Val});
-parse_property(<<16#15, Bin/binary>>, Props) ->
-    {Val, Rest} = parse_utf8_string(Bin),
-    parse_property(Rest, Props#{'Authentication-Method' => Val});
-parse_property(<<16#16, Len:16/big, Val:Len/binary, Bin/binary>>, Props) ->
-    parse_property(Bin, Props#{'Authentication-Data' => Val});
-parse_property(<<16#17, Val, Bin/binary>>, Props) ->
-    parse_property(Bin, Props#{'Request-Problem-Information' => Val});
-parse_property(<<16#18, Val:32, Bin/binary>>, Props) ->
-    parse_property(Bin, Props#{'Will-Delay-Interval' => Val});
-parse_property(<<16#19, Val, Bin/binary>>, Props) ->
-    parse_property(Bin, Props#{'Request-Response-Information' => Val});
-parse_property(<<16#1A, Bin/binary>>, Props) ->
-    {Val, Rest} = parse_utf8_string(Bin),
-    parse_property(Rest, Props#{'Response-Information' => Val});
-parse_property(<<16#1C, Bin/binary>>, Props) ->
-    {Val, Rest} = parse_utf8_string(Bin),
-    parse_property(Rest, Props#{'Server-Reference' => Val});
-parse_property(<<16#1F, Bin/binary>>, Props) ->
-    {Val, Rest} = parse_utf8_string(Bin),
-    parse_property(Rest, Props#{'Reason-String' => Val});
-parse_property(<<16#21, Val:16/big, Bin/binary>>, Props) ->
-    parse_property(Bin, Props#{'Receive-Maximum' => Val});
-parse_property(<<16#22, Val:16/big, Bin/binary>>, Props) ->
-    parse_property(Bin, Props#{'Topic-Alias-Maximum' => Val});
-parse_property(<<16#23, Val:16/big, Bin/binary>>, Props) ->
-    parse_property(Bin, Props#{'Topic-Alias' => Val});
-parse_property(<<16#24, Val, Bin/binary>>, Props) ->
-    parse_property(Bin, Props#{'Maximum-QoS' => Val});
-parse_property(<<16#25, Val, Bin/binary>>, Props) ->
-    parse_property(Bin, Props#{'Retain-Available' => Val});
-parse_property(<<16#26, Bin/binary>>, Props) ->
-    {Pair, Rest} = parse_utf8_pair(Bin),
+    parse_property(Rest, Props#{'Subscription-Identifier' => Val}, StrictMode);
+parse_property(<<16#11, Val:32/big, Bin/binary>>, Props, StrictMode) ->
+    parse_property(Bin, Props#{'Session-Expiry-Interval' => Val}, StrictMode);
+parse_property(<<16#12, Bin/binary>>, Props, StrictMode) ->
+    {Val, Rest} = parse_utf8_string(Bin, StrictMode),
+    parse_property(Rest, Props#{'Assigned-Client-Identifier' => Val}, StrictMode);
+parse_property(<<16#13, Val:16, Bin/binary>>, Props, StrictMode) ->
+    parse_property(Bin, Props#{'Server-Keep-Alive' => Val}, StrictMode);
+parse_property(<<16#15, Bin/binary>>, Props, StrictMode) ->
+    {Val, Rest} = parse_utf8_string(Bin, StrictMode),
+    parse_property(Rest, Props#{'Authentication-Method' => Val}, StrictMode);
+parse_property(<<16#16, Len:16/big, Val:Len/binary, Bin/binary>>, Props, StrictMode) ->
+    parse_property(Bin, Props#{'Authentication-Data' => Val}, StrictMode);
+parse_property(<<16#17, Val, Bin/binary>>, Props, StrictMode) ->
+    parse_property(Bin, Props#{'Request-Problem-Information' => Val}, StrictMode);
+parse_property(<<16#18, Val:32, Bin/binary>>, Props, StrictMode) ->
+    parse_property(Bin, Props#{'Will-Delay-Interval' => Val}, StrictMode);
+parse_property(<<16#19, Val, Bin/binary>>, Props, StrictMode) ->
+    parse_property(Bin, Props#{'Request-Response-Information' => Val}, StrictMode);
+parse_property(<<16#1A, Bin/binary>>, Props, StrictMode) ->
+    {Val, Rest} = parse_utf8_string(Bin, StrictMode),
+    parse_property(Rest, Props#{'Response-Information' => Val}, StrictMode);
+parse_property(<<16#1C, Bin/binary>>, Props, StrictMode) ->
+    {Val, Rest} = parse_utf8_string(Bin, StrictMode),
+    parse_property(Rest, Props#{'Server-Reference' => Val}, StrictMode);
+parse_property(<<16#1F, Bin/binary>>, Props, StrictMode) ->
+    {Val, Rest} = parse_utf8_string(Bin, StrictMode),
+    parse_property(Rest, Props#{'Reason-String' => Val}, StrictMode);
+parse_property(<<16#21, Val:16/big, Bin/binary>>, Props, StrictMode) ->
+    parse_property(Bin, Props#{'Receive-Maximum' => Val}, StrictMode);
+parse_property(<<16#22, Val:16/big, Bin/binary>>, Props, StrictMode) ->
+    parse_property(Bin, Props#{'Topic-Alias-Maximum' => Val}, StrictMode);
+parse_property(<<16#23, Val:16/big, Bin/binary>>, Props, StrictMode) ->
+    parse_property(Bin, Props#{'Topic-Alias' => Val}, StrictMode);
+parse_property(<<16#24, Val, Bin/binary>>, Props, StrictMode) ->
+    parse_property(Bin, Props#{'Maximum-QoS' => Val}, StrictMode);
+parse_property(<<16#25, Val, Bin/binary>>, Props, StrictMode) ->
+    parse_property(Bin, Props#{'Retain-Available' => Val}, StrictMode);
+parse_property(<<16#26, Bin/binary>>, Props, StrictMode) ->
+    {Pair, Rest} = parse_utf8_pair(Bin, StrictMode),
     case maps:find('User-Property', Props) of
         {ok, UserProps} ->
             UserProps1 = lists:append(UserProps, [Pair]),
-            parse_property(Rest, Props#{'User-Property' := UserProps1});
+            parse_property(Rest, Props#{'User-Property' := UserProps1}, StrictMode);
         error ->
-            parse_property(Rest, Props#{'User-Property' => [Pair]})
+            parse_property(Rest, Props#{'User-Property' => [Pair]}, StrictMode)
     end;
-parse_property(<<16#27, Val:32, Bin/binary>>, Props) ->
-    parse_property(Bin, Props#{'Maximum-Packet-Size' => Val});
-parse_property(<<16#28, Val, Bin/binary>>, Props) ->
-    parse_property(Bin, Props#{'Wildcard-Subscription-Available' => Val});
-parse_property(<<16#29, Val, Bin/binary>>, Props) ->
-    parse_property(Bin, Props#{'Subscription-Identifier-Available' => Val});
-parse_property(<<16#2A, Val, Bin/binary>>, Props) ->
-    parse_property(Bin, Props#{'Shared-Subscription-Available' => Val}).
+parse_property(<<16#27, Val:32, Bin/binary>>, Props, StrictMode) ->
+    parse_property(Bin, Props#{'Maximum-Packet-Size' => Val}, StrictMode);
+parse_property(<<16#28, Val, Bin/binary>>, Props, StrictMode) ->
+    parse_property(Bin, Props#{'Wildcard-Subscription-Available' => Val}, StrictMode);
+parse_property(<<16#29, Val, Bin/binary>>, Props, StrictMode) ->
+    parse_property(Bin, Props#{'Subscription-Identifier-Available' => Val}, StrictMode);
+parse_property(<<16#2A, Val, Bin/binary>>, Props, StrictMode) ->
+    parse_property(Bin, Props#{'Shared-Subscription-Available' => Val}, StrictMode);
+parse_property(<<Property:8, _Rest/binary>>, _Props, _StrictMode) ->
+    error(#{invalid_property_code => Property}).
+%% TODO: invalid property in specific packet.
 
 parse_variable_byte_integer(Bin) ->
     parse_variable_byte_integer(Bin, 1, 0).
@@ -445,20 +457,62 @@ parse_topic_filters(unsubscribe, Bin) ->
 parse_reason_codes(Bin) ->
     [Code || <<Code>> <= Bin].
 
-parse_utf8_pair(<<Len1:16/big, Key:Len1/binary,
-                  Len2:16/big, Val:Len2/binary, Rest/binary>>) ->
-    {{Key, Val}, Rest}.
+%%--------------------
+%% parse utf8 pair
+parse_utf8_pair( <<Len1:16/big, Key:Len1/binary,
+                   Len2:16/big, Val:Len2/binary, Rest/binary>>
+               , true) ->
+    {{validate_utf8(Key), validate_utf8(Val)}, Rest};
+parse_utf8_pair( <<Len1:16/big, Key:Len1/binary,
+                   Len2:16/big, Val:Len2/binary, Rest/binary>>
+               , false) ->
+    {{Key, Val}, Rest};
+parse_utf8_pair(<<LenK:16/big, Rest/binary>>, _StrictMode)
+  when LenK > byte_size(Rest) ->
+    error(user_property_not_enough_bytes);
+parse_utf8_pair(<<LenK:16/big, _Key:LenK/binary, %% key maybe malformed
+                  LenV:16/big, Rest/binary>>, _StrictMode)
+  when LenV > byte_size(Rest) ->
+    error(malformed_user_property_value);
+parse_utf8_pair(Bin, _StrictMode)
+  when 4 > byte_size(Bin) ->
+    error(user_property_not_enough_bytes).
 
-parse_utf8_string(Bin, false) ->
+%%--------------------
+%% parse utf8 string
+parse_utf8_string(Bin, _StrictMode, false) ->
     {undefined, Bin};
-parse_utf8_string(Bin, true) ->
-    parse_utf8_string(Bin).
+parse_utf8_string(Bin, StrictMode, true) ->
+    parse_utf8_string(Bin, StrictMode).
 
-parse_utf8_string(<<Len:16/big, Str:Len/binary, Rest/binary>>) ->
-    {Str, Rest}.
+parse_utf8_string(<<Len:16/big, Str:Len/binary, Rest/binary>>, true) ->
+    {validate_utf8(Str), Rest};
+parse_utf8_string(<<Len:16/big, Str:Len/binary, Rest/binary>>, false) ->
+    {Str, Rest};
+parse_utf8_string(<<Len:16/big, Rest/binary>>, _)
+  when Len > byte_size(Rest) ->
+    error(malformed_utf8_string);
+parse_utf8_string(Bin, _)
+  when 2 > byte_size(Bin) ->
+    error(malformed_utf8_string_length).
 
 parse_binary_data(<<Len:16/big, Data:Len/binary, Rest/binary>>) ->
-    {Data, Rest}.
+    {Data, Rest};
+parse_binary_data(<<Len:16/big, Rest/binary>>)
+  when Len > byte_size(Rest) ->
+    error(malformed_binary_data);
+parse_binary_data(Bin)
+  when 2 > byte_size(Bin) ->
+    error(malformed_binary_data_length).
+
+ensure_topic_name_valid(false, _TopicName, _Properties) ->
+    ok;
+ensure_topic_name_valid(true, TopicName, _Properties) when TopicName =/= <<>> ->
+    ok;
+ensure_topic_name_valid(true, <<>>, #{'Topic-Alias' := _}) ->
+    ok;
+ensure_topic_name_valid(true, <<>>, _) ->
+    error(empty_topic_name).
 
 %%--------------------------------------------------------------------
 %% Serialize MQTT Packet
@@ -796,3 +850,52 @@ fixqos(?PUBREL, 0)      -> 1;
 fixqos(?SUBSCRIBE, 0)   -> 1;
 fixqos(?UNSUBSCRIBE, 0) -> 1;
 fixqos(_Type, QoS)      -> QoS.
+
+validate_utf8(Bin) ->
+    case unicode:characters_to_binary(Bin) of
+        {error, _, _} ->
+            error(utf8_string_invalid);
+        {incomplete, _, _} ->
+            error(utf8_string_invalid);
+        Bin when is_binary(Bin) ->
+            case validate_mqtt_utf8_char(Bin) of
+                true -> Bin;
+                false -> error(utf8_string_invalid)
+            end
+    end.
+
+%% Is the utf8 string respecting UTF-8 characters defined by MQTT Spec?
+%% i.e. contains invalid UTF-8 char or control char
+validate_mqtt_utf8_char(<<>>) ->
+    true;
+%% ==== 1-Byte UTF-8 invalid: [[U+0000 .. U+001F] && [U+007F]]
+validate_mqtt_utf8_char(<<B1, Bs/binary>>)
+  when B1 >= 16#20, B1 =< 16#7E ->
+    validate_mqtt_utf8_char(Bs);
+validate_mqtt_utf8_char(<<B1, _Bs/binary>>)
+  when B1 >=  16#00, B1 =< 16#1F;
+       B1 =:= 16#7F ->
+    %% [U+0000 .. U+001F] && [U+007F]
+    false;
+%% ==== 2-Bytes UTF-8 invalid: [U+0080 .. U+009F]
+validate_mqtt_utf8_char(<<B1, B2, Bs/binary>>)
+  when B1 =:= 16#C2;
+       B2 >=  16#A0, B2 =< 16#BF;
+       B1  >  16#C3, B1 =< 16#DE;
+       B2 >=  16#80, B2 =< 16#BF ->
+    validate_mqtt_utf8_char(Bs);
+validate_mqtt_utf8_char(<<16#C2, B2, _Bs/binary>>)
+  when B2 >= 16#80, B2 =< 16#9F ->
+    %% [U+0080 .. U+009F]
+    false;
+%% ==== 3-Bytes UTF-8 invalid: [U+D800 .. U+DFFF]
+validate_mqtt_utf8_char(<<B1, _B2, _B3, Bs/binary>>)
+  when B1 >= 16#E0, B1 =< 16#EE;
+       B1 =:= 16#EF ->
+    validate_mqtt_utf8_char(Bs);
+validate_mqtt_utf8_char(<<16#ED, _B2, _B3, _Bs/binary>>) ->
+    false;
+%% ==== 4-Bytes UTF-8
+validate_mqtt_utf8_char(<<B1, _B2, _B3, _B4, Bs/binary>>)
+  when B1 =:= 16#0F ->
+    validate_mqtt_utf8_char(Bs).
diff --git a/src/emqx_limiter.erl b/src/emqx_limiter.erl
index 8acd50d32..4fe3a98e1 100644
--- a/src/emqx_limiter.erl
+++ b/src/emqx_limiter.erl
@@ -23,7 +23,8 @@
         , init/4 %% XXX: Compatible with before 4.2 version
         , info/1
         , check/2
-        , update_overall_limiter/4
+        , update_overall_limiter/3
+        , delete_overall_limiter/1
         ]).
 
 -record(limiter, {
@@ -154,14 +155,18 @@ is_message_limiter(conn_messages_routing) -> true;
 is_message_limiter(overall_messages_routing) -> true;
 is_message_limiter(_) -> false.
 
-update_overall_limiter(Zone, Name, Capacity, Interval) ->
-    case is_overall_limiter(Name) of
-        false -> false;
-        _ ->
-            try
-                esockd_limiter:update({Zone, Name}, Capacity, Interval),
-                true
-            catch _:_:_ ->
-                    false
-            end
+update_overall_limiter(Zone, Capacity, Interval) ->
+    try
+        esockd_limiter:update({Zone, overall_messages_routing}, Capacity, Interval),
+        true
+    catch _:_:_ ->
+        false
+    end.
+
+delete_overall_limiter(Zone) ->
+    try
+        esockd_limiter:delete({Zone, overall_messages_routing}),
+        true
+    catch _:_:_ ->
+        false
     end.
diff --git a/src/emqx_listeners.erl b/src/emqx_listeners.erl
index ce256d147..7dbd2c37d 100644
--- a/src/emqx_listeners.erl
+++ b/src/emqx_listeners.erl
@@ -29,6 +29,7 @@
         , start_listener/3
         , stop_listener/1
         , stop_listener/3
+        , update_listeners_env/2
         , restart_listener/1
         , restart_listener/3
         ]).
@@ -114,6 +115,20 @@ with_port({Addr, Port}, Opts = #{socket_opts := SocketOption}) ->
 restart() ->
     lists:foreach(fun restart_listener/1, emqx:get_env(listeners, [])).
 
+update_listeners_env(Action, NewConf = #{name := NewName, proto := NewProto}) ->
+    Listener = emqx:get_env(listeners, []),
+    Listener1 = lists:filter(
+        fun(#{name := Name, proto := Proto}) ->
+            not (Name =:= NewName andalso Proto =:= NewProto)
+        end, Listener),
+    Listener2 =
+        case Action of
+            update -> [NewConf | Listener1];
+            delete -> Listener1
+        end,
+    application:set_env(emqx, listeners, Listener2),
+    ok.
+
 -spec(restart_listener(listener()) -> any()).
 restart_listener({Proto, ListenOn, Options}) ->
     restart_listener(Proto, ListenOn, Options).
diff --git a/src/emqx_message.erl b/src/emqx_message.erl
index decbb0c18..7c626fa94 100644
--- a/src/emqx_message.erl
+++ b/src/emqx_message.erl
@@ -298,7 +298,8 @@ elapsed(Since) ->
 
 format(#message{id = Id, qos = QoS, topic = Topic, from = From, flags = Flags, headers = Headers}) ->
     io_lib:format("Message(Id=~s, QoS=~w, Topic=~s, From=~p, Flags=~s, Headers=~s)",
-                  [Id, QoS, Topic, From, format(flags, Flags), format(headers, Headers)]).
+                  [emqx_guid:to_hexstr(Id), QoS, Topic, From, format(flags, Flags),
+                   format(headers, Headers)]).
 
 format(flags, Flags) ->
     io_lib:format("~p", [[Flag || {Flag, true} <- maps:to_list(Flags)]]);
diff --git a/src/emqx_os_mon.erl b/src/emqx_os_mon.erl
index 2852c917b..5e580e032 100644
--- a/src/emqx_os_mon.erl
+++ b/src/emqx_os_mon.erl
@@ -81,7 +81,7 @@ get_mem_check_interval() ->
 
 set_mem_check_interval(Seconds) when Seconds < 60 ->
     memsup:set_check_interval(1);
-set_mem_check_interval(Seconds) -> 
+set_mem_check_interval(Seconds) ->
     memsup:set_check_interval(Seconds div 60).
 
 get_sysmem_high_watermark() ->
@@ -105,8 +105,10 @@ call(Req) ->
 
 init([Opts]) ->
     set_mem_check_interval(proplists:get_value(mem_check_interval, Opts)),
-    set_sysmem_high_watermark(proplists:get_value(sysmem_high_watermark, Opts)),
+    HW = proplists:get_value(sysmem_high_watermark, Opts),
+    set_sysmem_high_watermark(HW),
     set_procmem_high_watermark(proplists:get_value(procmem_high_watermark, Opts)),
+    ensure_system_memory_alarm(HW),
     {ok, ensure_check_timer(#{cpu_high_watermark => proplists:get_value(cpu_high_watermark, Opts),
                               cpu_low_watermark => proplists:get_value(cpu_low_watermark, Opts),
                               cpu_check_interval => proplists:get_value(cpu_check_interval, Opts),
@@ -177,3 +179,20 @@ ensure_check_timer(State = #{cpu_check_interval := Interval}) ->
         "x86_64-pc-linux-musl" -> State;
         _ -> State#{timer := emqx_misc:start_timer(timer:seconds(Interval), check)}
     end.
+
+%% At startup, memsup starts first and checks for memory alarms,
+%% but emqx_alarm_handler is not yet used instead of alarm_handler,
+%% so alarm_handler is used directly for notification (normally emqx_alarm_handler should be used).
+%%The internal memsup will no longer trigger events that have been alerted,
+%% and there is no exported function to remove the alerted flag,
+%% so it can only be checked again at startup.
+ensure_system_memory_alarm(HW) ->
+    case erlang:whereis(memsup) of
+        undefined -> ok;
+        _Pid ->
+            {Total, Allocated, _Worst} = memsup:get_memory_data(),
+            case Total =/= 0 andalso Allocated/Total * 100 >= HW of
+                true -> emqx_alarm:activate(high_system_memory_usage, #{high_watermark => HW});
+                false -> ok
+            end
+    end.
diff --git a/src/emqx_plugins.erl b/src/emqx_plugins.erl
index faa6abae3..e22cd2058 100644
--- a/src/emqx_plugins.erl
+++ b/src/emqx_plugins.erl
@@ -103,7 +103,7 @@ unload(PluginName) when is_atom(PluginName) ->
             ?LOG(error, "Plugin ~s is not started", [PluginName]),
             {error, not_started};
         {_, _} ->
-            unload_plugin(PluginName, true)            
+            unload_plugin(PluginName, true)
     end.
 
 reload(PluginName) when is_atom(PluginName)->
@@ -204,10 +204,21 @@ with_loaded_file(File, SuccFun) ->
     end.
 
 filter_plugins(Names) ->
-    lists:filtermap(fun(Name1) when is_atom(Name1) -> {true, Name1};
-                       ({Name1, true}) -> {true, Name1};
-                       ({_Name1, false}) -> false
-                    end, Names).
+    filter_plugins(Names, []).
+
+filter_plugins([], Plugins) ->
+    lists:reverse(Plugins);
+filter_plugins([{Name, Load} | Names], Plugins) ->
+    case {Load, lists:member(Name, Plugins)} of
+        {true, false} ->
+            filter_plugins(Names, [Name | Plugins]);
+        {false, true} ->
+            filter_plugins(Names, Plugins -- [Name]);
+        _ ->
+            filter_plugins(Names, Plugins)
+    end;
+filter_plugins([Name | Names], Plugins) when is_atom(Name) ->
+    filter_plugins([{Name, true} | Names], Plugins).
 
 load_plugins(Names, Persistent) ->
     Plugins = list(), NotFound = Names -- names(Plugins),
diff --git a/src/emqx_sys.erl b/src/emqx_sys.erl
index 38387b3ce..4bfe20a89 100644
--- a/src/emqx_sys.erl
+++ b/src/emqx_sys.erl
@@ -96,7 +96,15 @@ sysdescr() ->
 %% @doc Get sys uptime
 -spec(uptime() -> string()).
 uptime() ->
-    gen_server:call(?SYS, uptime).
+    {TotalWallClock, _} = erlang:statistics(wall_clock),
+    uptime(TotalWallClock div 1000).
+
+uptime(Seconds) ->
+    {D, {H, M, S}} = calendar:seconds_to_daystime(Seconds),
+    L0 = [{D, " days"}, {H, " hours"}, {M, " minutes"}, {S, " seconds"}],
+    L1 = lists:dropwhile(fun({K, _}) ->  K =:= 0 end, L0),
+    L2 = lists:map(fun({Time, Unit}) -> [integer_to_list(Time), Unit] end, L1),
+    lists:flatten(lists:join(", ", L2)).
 
 %% @doc Get sys datetime
 -spec(datetime() -> string()).
@@ -139,9 +147,6 @@ heartbeat(State) ->
 tick(State) ->
     State#state{ticker = start_timer(sys_interval(), tick)}.
 
-handle_call(uptime, _From, State) ->
-    {reply, uptime(State), State};
-
 handle_call(Req, _From, State) ->
     ?LOG(error, "Unexpected call: ~p", [Req]),
     {reply, ignored, State}.
@@ -151,7 +156,7 @@ handle_cast(Msg, State) ->
     {noreply, State}.
 
 handle_info({timeout, TRef, heartbeat}, State = #state{heartbeat = TRef}) ->
-    publish(uptime, iolist_to_binary(uptime(State))),
+    publish(uptime, iolist_to_binary(uptime())),
     publish(datetime, iolist_to_binary(datetime())),
     {noreply, heartbeat(State)};
 
@@ -174,24 +179,6 @@ terminate(_Reason, #state{heartbeat = TRef1, ticker = TRef2}) ->
 %% Internal functions
 %%-----------------------------------------------------------------------------
 
-uptime(#state{start_time = Ts}) ->
-    Secs = timer:now_diff(erlang:timestamp(), Ts) div 1000000,
-    lists:flatten(uptime(seconds, Secs)).
-uptime(seconds, Secs) when Secs < 60 ->
-    [integer_to_list(Secs), " seconds"];
-uptime(seconds, Secs) ->
-    [uptime(minutes, Secs div 60), integer_to_list(Secs rem 60), " seconds"];
-uptime(minutes, M) when M < 60 ->
-    [integer_to_list(M), " minutes, "];
-uptime(minutes, M) ->
-    [uptime(hours, M div 60), integer_to_list(M rem 60), " minutes, "];
-uptime(hours, H) when H < 24 ->
-    [integer_to_list(H), " hours, "];
-uptime(hours, H) ->
-    [uptime(days, H div 24), integer_to_list(H rem 24), " hours, "];
-uptime(days, D) ->
-    [integer_to_list(D), " days, "].
-
 publish(uptime, Uptime) ->
     safe_publish(systop(uptime), Uptime);
 publish(datetime, Datetime) ->
diff --git a/test/emqx_frame_SUITE.erl b/test/emqx_frame_SUITE.erl
index aef88cf9f..eca130bbe 100644
--- a/test/emqx_frame_SUITE.erl
+++ b/test/emqx_frame_SUITE.erl
@@ -43,7 +43,12 @@ groups() ->
     [{parse, [parallel],
       [t_parse_cont,
        t_parse_frame_too_large,
-       t_parse_frame_malformed_variable_byte_integer
+       t_parse_frame_malformed_variable_byte_integer,
+       t_parse_frame_variable_byte_integer,
+       t_parse_malformed_utf8_string,
+       t_parse_empty_topic_name,
+       t_parse_empty_topic_name_with_alias,
+       t_parse_frame_proxy_protocol %% proxy_protocol_config_disabled packet.
       ]},
      {connect, [parallel],
       [t_serialize_parse_v3_connect,
@@ -136,6 +141,50 @@ t_parse_frame_malformed_variable_byte_integer(_) ->
     ?catch_error(malformed_variable_byte_integer,
         emqx_frame:parse(MalformedPayload, ParseState)).
 
+t_parse_frame_variable_byte_integer(_) ->
+    Bin = <<2#10010011, 2#10000000, 2#10001000, 2#10011001, 2#10101101, 2#00110010>>,
+    ?catch_error(malformed_variable_byte_integer,
+        emqx_frame:parse_variable_byte_integer(Bin)).
+
+t_parse_malformed_utf8_string(_) ->
+    MalformedPacket = <<16,31,0,4,
+                        %% Specification name, should be "MQTT"
+                        %% 77,81,84,84,
+                        %% malformed 1-Byte UTF-8 in (U+0000 .. U+001F] && [U+007F])
+                        16#00,16#01,16#1F,16#7F,
+
+                        4,194,0,60,
+                        0,4,101,109,
+                        113,120,0,5,
+                        97,100,109,105,
+                        110,0,6,112,
+                        117,98,108,105,
+                        99>>,
+    ParseState = emqx_frame:initial_parse_state(#{strict_mode => true}),
+    ?catch_error(utf8_string_invalid, emqx_frame:parse(MalformedPacket, ParseState)).
+
+t_parse_empty_topic_name(_) ->
+    Packet = ?PUBLISH_PACKET(?QOS_1, <<>>, 1, #{}, <<>>),
+    ?assertEqual(Packet, parse_serialize(Packet, #{strict_mode => false})),
+    ?catch_error(empty_topic_name, parse_serialize(Packet, #{strict_mode => true})).
+
+t_parse_empty_topic_name_with_alias(_) ->
+    Props = #{'Topic-Alias' => 16#AB},
+    Packet = ?PUBLISH_PACKET(?QOS_1, <<>>, 1, Props, <<>>),
+    ?assertEqual(
+       Packet, parse_serialize(Packet, #{strict_mode => false, version => ?MQTT_PROTO_V5})
+      ),
+    ?assertEqual(
+       Packet, parse_serialize(Packet, #{strict_mode => true, version => ?MQTT_PROTO_V5})
+      ).
+
+t_parse_frame_proxy_protocol(_) ->
+    BinList = [ <<"PROXY TCP4 ">>, <<"PROXY TCP6 ">>, <<"PROXY UNKNOWN">>
+              , <<"\r\n\r\n\0\r\nQUIT\n">>],
+    [?assertError( proxy_protocol_config_disabled
+                 , emqx_frame:parse(Bin))
+     || Bin <- BinList].
+
 t_serialize_parse_v3_connect(_) ->
     Bin = <<16,37,0,6,77,81,73,115,100,112,3,2,0,60,0,23,109,111,115,
             113,112,117, 98,47,49,48,52,53,49,45,105,77,97,99,46,108,
@@ -531,4 +580,3 @@ parse_to_packet(Bin, Opts) ->
     Packet.
 
 payload(Len) -> iolist_to_binary(lists:duplicate(Len, 1)).
-
diff --git a/test/emqx_os_mon_SUITE.erl b/test/emqx_os_mon_SUITE.erl
index cb57b900f..07a7a5271 100644
--- a/test/emqx_os_mon_SUITE.erl
+++ b/test/emqx_os_mon_SUITE.erl
@@ -24,10 +24,23 @@
 all() -> emqx_ct:all(?MODULE).
 
 init_per_suite(Config) ->
+    emqx_ct_helpers:boot_modules(all),
+    emqx_ct_helpers:start_apps([],
+        fun(emqx) ->
+            application:set_env(emqx, os_mon, [
+                {cpu_check_interval, 1},
+                {cpu_high_watermark, 5},
+                {cpu_low_watermark, 80},
+                {mem_check_interval, 60},
+                {sysmem_high_watermark, 70},
+                {procmem_high_watermark, 5}]);
+            (_) -> ok
+        end),
     application:ensure_all_started(os_mon),
     Config.
 
 end_per_suite(_Config) ->
+    emqx_ct_helpers:stop_apps([]),
     application:stop(os_mon).
 
 % t_set_mem_check_interval(_) ->
@@ -40,13 +53,6 @@ end_per_suite(_Config) ->
 %     error('TODO').
 
 t_api(_) ->
-    gen_event:swap_handler(alarm_handler, {emqx_alarm_handler, swap}, {alarm_handler, []}),
-    {ok, _} = emqx_os_mon:start_link([{cpu_check_interval, 1},
-                                      {cpu_high_watermark, 5},
-                                      {cpu_low_watermark, 80},
-                                      {mem_check_interval, 60},
-                                      {sysmem_high_watermark, 70},
-                                      {procmem_high_watermark, 5}]),
     ?assertEqual(1, emqx_os_mon:get_cpu_check_interval()),
     ?assertEqual(5, emqx_os_mon:get_cpu_high_watermark()),
     ?assertEqual(80, emqx_os_mon:get_cpu_low_watermark()),
@@ -69,4 +75,3 @@ t_api(_) ->
     emqx_os_mon ! ignored,
     gen_server:stop(emqx_os_mon),
     ok.
-
diff --git a/test/emqx_sys_SUITE.erl b/test/emqx_sys_SUITE.erl
index 0814f8b00..c6d95b8ac 100644
--- a/test/emqx_sys_SUITE.erl
+++ b/test/emqx_sys_SUITE.erl
@@ -34,7 +34,7 @@ end_per_suite(_Config) ->
     application:unload(emqx),
     ok = emqx_logger:set_log_level(error),
     ok.
-    
+
 % t_version(_) ->
 %     error('TODO').
 
@@ -42,10 +42,24 @@ end_per_suite(_Config) ->
 %     error('TODO').
 
 t_uptime(_) ->
-    ?assertEqual(<<"1 seconds">>, iolist_to_binary(emqx_sys:uptime(seconds, 1))),
-    ?assertEqual(<<"1 minutes, 0 seconds">>, iolist_to_binary(emqx_sys:uptime(seconds, 60))),
-    ?assertEqual(<<"1 hours, 0 minutes, 0 seconds">>, iolist_to_binary(emqx_sys:uptime(seconds, 3600))),
-    ?assertEqual(<<"1 days, 0 hours, 0 minutes, 0 seconds">>, iolist_to_binary(emqx_sys:uptime(seconds, 86400))).
+    ?assert(is_list(emqx_sys:uptime())),
+    ?assertEqual(<<"1 seconds">>, iolist_to_binary(emqx_sys:uptime(1))),
+    ?assertEqual(<<"1 minutes, 0 seconds">>, iolist_to_binary(emqx_sys:uptime(60))),
+    ?assertEqual(<<"1 hours, 0 minutes, 0 seconds">>, iolist_to_binary(emqx_sys:uptime(3600))),
+    ?assertEqual(<<"1 hours, 1 minutes, 1 seconds">>, iolist_to_binary(emqx_sys:uptime(3661))),
+    ?assertEqual(<<"1 days, 0 hours, 0 minutes, 0 seconds">>,
+        iolist_to_binary(emqx_sys:uptime(86400))),
+    lists:map(fun({D, H, M, S}) ->
+        Expect = <<
+            (integer_to_binary(D))/binary, " days, ",
+            (integer_to_binary(H))/binary, " hours, ",
+            (integer_to_binary(M))/binary, " minutes, ",
+            (integer_to_binary(S))/binary, " seconds"
+        >>,
+        Actual = iolist_to_binary(emqx_sys:uptime(D * 86400 + H * 3600 + M * 60 + S)),
+        ?assertEqual(Expect, Actual)
+              end,
+        [{1, 2, 3, 4}, {10, 20, 30, 40}, {2222, 3, 56, 59}, {59, 23, 59, 59}]).
 
 % t_datetime(_) ->
 %     error('TODO').