chore(emqx_retainer): refresh the timestamp when dispatch retained message (#6155)

1. refresh the timestamp when dispatch retained message
2. fix some elvis style error

apps/emqx_retainer/src/emqx_retainer.app.src

@@ -1,6 +1,6 @@
 {application, emqx_retainer,
  [{description, "EMQ X Retainer"},
-  {vsn, "4.4.0"}, % strict semver, bump manually!
+  {vsn, "4.4.1"}, % strict semver, bump manually!
   {modules, []},
   {registered, [emqx_retainer_sup]},
   {applications, [kernel,stdlib]},

apps/emqx_retainer/src/emqx_retainer.erl

@@ -78,7 +78,8 @@ dispatch(Pid, Topic) ->
                false -> read_messages(Topic);
                true  -> match_messages(Topic)
            end,
-    [Pid ! {deliver, Topic, Msg} || Msg  <- sort_retained(Msgs)].
+    Now = erlang:system_time(millisecond),
+    [Pid ! {deliver, Topic, refresh_timestamp_expiry(Msg, Now)} || Msg  <- sort_retained(Msgs)].
 
 %% RETAIN flag set to 1 and payload containing zero bytes
 on_message_publish(Msg = #message{flags   = #{retain := true},
@@ -146,7 +147,7 @@ init([Env]) ->
             ok
     end,
     StatsFun = emqx_stats:statsfun('retained.count', 'retained.max'),
-    {ok, StatsTimer} = timer:send_interval(timer:seconds(1), stats),
+    StatsTimer = erlang:send_after(timer:seconds(1), self(), stats),
     State = #state{stats_fun = StatsFun, stats_timer = StatsTimer},
     {ok, start_expire_timer(proplists:get_value(expiry_interval, Env, 0), State)}.
 
@@ -155,7 +156,7 @@ start_expire_timer(0, State) ->
 start_expire_timer(undefined, State) ->
     State;
 start_expire_timer(Ms, State) ->
-    {ok, Timer} = timer:send_interval(Ms, expire),
+    Timer = erlang:send_after(Ms, self(), stats),
     State#state{expiry_timer = Timer}.
 
 handle_call(Req, _From, State) ->
@@ -194,7 +195,7 @@ sort_retained([]) -> [];
 sort_retained([Msg]) -> [Msg];
 sort_retained(Msgs)  ->
     lists:sort(fun(#message{timestamp = Ts1}, #message{timestamp = Ts2}) ->
-                   Ts1 =< Ts2
+                       Ts1 =< Ts2
                end, Msgs).
 
 store_retained(Msg = #message{topic = Topic, payload = Payload}, Env) ->
@@ -209,11 +210,13 @@ store_retained(Msg = #message{topic = Topic, payload = Payload}, Env) ->
                 fun() ->
                     case mnesia:read(?TAB, Topic) of
                         [_] ->
-                            mnesia:write(?TAB, #retained{topic = topic2tokens(Topic),
+                            mnesia:write(?TAB,
-                                                         msg = Msg,
+                                         #retained{topic = topic2tokens(Topic),
-                                                         expiry_time = get_expiry_time(Msg, Env)}, write);
+                                                   msg = Msg,
+                                                   expiry_time = get_expiry_time(Msg, Env)}, write);
                         [] ->
-                            ?LOG(error, "Cannot retain message(topic=~s) for table is full!", [Topic])
+                            ?LOG(error,
+                                 "Cannot retain message(topic=~s) for table is full!", [Topic])
                     end
                 end),
             ok;
@@ -234,7 +237,8 @@ is_too_big(Size, Env) ->
 
 get_expiry_time(#message{headers = #{properties := #{'Message-Expiry-Interval' := 0}}}, _Env) ->
     0;
-get_expiry_time(#message{headers = #{properties := #{'Message-Expiry-Interval' := Interval}}, timestamp = Ts}, _Env) ->
+get_expiry_time(#message{headers = #{properties := #{'Message-Expiry-Interval' := Interval}},
+                         timestamp = Ts}, _Env) ->
     Ts + Interval * 1000;
 get_expiry_time(#message{timestamp = Ts}, Env) ->
     case proplists:get_value(expiry_interval, Env, 0) of
@@ -303,3 +307,18 @@ condition(Ws) ->
         false -> Ws1;
         _ -> (Ws1 -- ['#']) ++ '_'
     end.
+
+-spec(refresh_timestamp_expiry(emqx_types:message(), pos_integer()) -> emqx_types:message()).
+refresh_timestamp_expiry(Msg = #message{headers =
+                                            #{properties :=
+                                                  #{'Message-Expiry-Interval' := Interval} = Props},
+                                        timestamp = CreatedAt},
+                         Now) ->
+    Elapsed = max(0, Now - CreatedAt),
+    Interval1 = max(1, Interval - (Elapsed div 1000)),
+    emqx_message:set_header(properties,
+                            Props#{'Message-Expiry-Interval' => Interval1},
+                            Msg#message{timestamp = Now});
+
+refresh_timestamp_expiry(Msg, Now) ->
+    Msg#message{timestamp = Now}.