diff --git a/src/emqx_alarm_handler.erl b/src/emqx_alarm_handler.erl
index 77cc09c60..e84665488 100644
--- a/src/emqx_alarm_handler.erl
+++ b/src/emqx_alarm_handler.erl
@@ -38,10 +38,11 @@
 -export([ load/0
         , unload/0
         , get_alarms/0
+        , get_alarms/1
         ]).
 
 -record(common_alarm, {id, desc}).
--record(alarm_history, {id, clear_at}).
+-record(alarm_history, {id, desc, clear_at}).
 
 -define(ALARM_TAB, emqx_alarm).
 -define(ALARM_HISTORY_TAB, emqx_alarm_history).
@@ -79,7 +80,14 @@ unload() ->
     gen_event:swap_handler(alarm_handler, {?MODULE, swap}, {alarm_handler, []}).
 
 get_alarms() ->
-    gen_event:call(alarm_handler, ?MODULE, get_alarms).
+    get_alarms(present).
+
+get_alarms(present) ->
+    Alarms = ets:tab2list(?ALARM_TAB),
+    [{Id, Desc} || #common_alarm{id = Id, desc = Desc} <- Alarms];
+get_alarms(history) ->
+    Alarms = ets:tab2list(?ALARM_HISTORY_TAB),
+    [{Id, Desc, ClearAt} || #alarm_history{id = Id, desc = Desc, clear_at = ClearAt} <- Alarms].
 
 %%----------------------------------------------------------------------
 %% gen_event callbacks
@@ -117,14 +125,14 @@ handle_event({clear_alarm, AlarmId}, State) ->
 handle_event(_, State) ->
     {ok, State}.
 
-handle_info(_, State) -> {ok, State}.
+handle_info(_, State) ->
+    {ok, State}.
 
-handle_call(get_alarms, State) ->
-    {ok, get_alarms_(), State};
-handle_call(_Query, State)     -> {ok, {error, bad_query}, State}.
+handle_call(_Query, State) ->
+    {ok, {error, bad_query}, State}.
 
 terminate(swap, _State) ->
-    {emqx_alarm_handler, get_alarms_()};
+    {emqx_alarm_handler, get_alarms()};
 terminate(_, _) ->
     ok.
 
@@ -134,8 +142,8 @@ terminate(_, _) ->
 
 init_tables(ExistingAlarms) ->
     mnesia:clear_table(?ALARM_TAB),
-    lists:foreach(fun({Id, _Desc}) ->
-                      set_alarm_history(Id)
+    lists:foreach(fun({Id, Desc}) ->
+                      set_alarm_history(Id, Desc)
                   end, ExistingAlarms).
 
 encode_alarm({AlarmId, #alarm{severity  = Severity,
@@ -146,12 +154,12 @@ encode_alarm({AlarmId, #alarm{severity  = Severity,
                            {desc, [{severity, Severity},
                                    {title, iolist_to_binary(Title)},
                                    {summary, iolist_to_binary(Summary)},
-                                   {ts, emqx_time:now_secs(Ts)}]}]);
+                                   {timestamp, emqx_time:now_ms(Ts)}]}]);
 encode_alarm({AlarmId, undefined}) ->
     emqx_json:safe_encode([{id, maybe_to_binary(AlarmId)}]);
 encode_alarm({AlarmId, AlarmDesc}) ->
     emqx_json:safe_encode([{id, maybe_to_binary(AlarmId)},
-                           {description, maybe_to_binary(AlarmDesc)}]).
+                           {desc, maybe_to_binary(AlarmDesc)}]).
 
 alarm_msg(Topic, Payload) ->
     Msg = emqx_message:make(?MODULE, Topic, Payload),
@@ -172,14 +180,15 @@ set_alarm_(Id, Desc) ->
     mnesia:dirty_write(?ALARM_TAB, #common_alarm{id = Id, desc = Desc}).
 
 clear_alarm_(Id) ->
-    mnesia:dirty_delete(?ALARM_TAB, Id),
-    set_alarm_history(Id).
+    case mnesia:dirty_read(?ALARM_TAB, Id) of
+        [#common_alarm{desc = Desc}] ->
+            set_alarm_history(Id, Desc),
+            mnesia:dirty_delete(?ALARM_TAB, Id);
+        [] -> ok
+    end.
 
-get_alarms_() ->
-    Alarms = ets:tab2list(?ALARM_TAB),
-    [{Id, Desc} || #common_alarm{id = Id, desc = Desc} <- Alarms].
-
-set_alarm_history(Id) ->
+set_alarm_history(Id, Desc) ->
     mnesia:dirty_write(?ALARM_HISTORY_TAB, #alarm_history{id = Id,
-                                                          clear_at = undefined}).
+                                                          desc = Desc,
+                                                          clear_at = os:timestamp()}).