fix issue #182 - etained message expiration

rel/files/emqttd.config.development

@@ -132,8 +132,12 @@
 
         %% Retained messages
         {retained, [
+            %% Expired after seconds, never expired if 0
+            {expired_after, 0},
+
             %% Max number of retained messages
             {max_message_num, 100000},
+
             %% Max Payload Size of retained message
             {max_playload_size, 65536}
         ]},

rel/files/emqttd.config.production

@@ -124,8 +124,12 @@
 
         %% Retained messages
         {retained, [
+            %% Expired after seconds, never expired if 0
+            {expired_after, 0},
+
             %% Max number of retained messages
             {max_message_num, 100000},
+
             %% Max Payload Size of retained message
             {max_playload_size, 65536}
         ]},

src/emqttd_app.erl

@@ -75,6 +75,7 @@ start_listeners() ->
 start_servers(Sup) ->
     Servers = [{"emqttd ctl", emqttd_ctl},
                {"emqttd trace", emqttd_trace},
+               {"emqttd retained", emqttd_retained},
                {"emqttd pooler", {supervisor, emqttd_pooler_sup}},
                {"emqttd client manager", {supervisor, emqttd_cm_sup}},
                {"emqttd session manager", {supervisor, emqttd_sm_sup}},

src/emqttd_retained.erl

@@ -31,6 +31,8 @@
 
 -include("emqttd.hrl").
 
+-include_lib("stdlib/include/ms_transform.hrl").
+
 %% Mnesia callbacks
 -export([mnesia/1]).
 
@@ -40,8 +42,19 @@
 %% API Function Exports
 -export([retain/1, dispatch/2]).
 
+%% API Function Exports
+-export([start_link/0, expire/1]).
+
+-behaviour(gen_server).
+
+%% gen_server Function Exports
+-export([init/1, handle_call/3, handle_cast/2, handle_info/2,
+         terminate/2, code_change/3]).
+
 -record(mqtt_retained, {topic, message}).
 
+-record(state, {stats_fun, expired_after, stats_timer, expire_timer}).
+
 %%%=============================================================================
 %%% Mnesia callbacks
 %%%=============================================================================
@@ -60,6 +73,14 @@ mnesia(copy) ->
 %%% API
 %%%=============================================================================
 
+%%------------------------------------------------------------------------------
+%% @doc Start a retained server
+%% @end
+%%------------------------------------------------------------------------------
+-spec start_link() -> {ok, pid()} | ignore | {error, any()}.
+start_link() ->
+    gen_server:start_link({local, ?MODULE}, ?MODULE, [], []).
+
 %%%-----------------------------------------------------------------------------
 %% @doc Retain message
 %% @end
@@ -71,9 +92,7 @@ retain(#mqtt_message{retain = false}) -> ignore;
 retain(#mqtt_message{retain = true, topic = Topic, payload = <<>>}) ->
     mnesia:async_dirty(fun mnesia:delete/1, [{retained, Topic}]);
 
-retain(Msg = #mqtt_message{topic = Topic,
-                           retain = true,
-                           payload = Payload}) ->
+retain(Msg = #mqtt_message{topic = Topic, retain = true, payload = Payload}) ->
     TabSize = mnesia:table_info(retained, size),
     case {TabSize < limit(table), size(Payload) < limit(payload)} of
         {true, true} ->
@@ -82,23 +101,23 @@ retain(Msg = #mqtt_message{topic = Topic,
             mnesia:async_dirty(fun mnesia:write/3, [retained, Retained, write]),
             emqttd_metrics:set('messages/retained', mnesia:table_info(retained, size));
        {false, _}->
-            lager:error("Dropped retained message(topic=~s) for table is full!", [Topic]);
+            lager:error("Cannot retain message(topic=~s) for table is full!", [Topic]);
        {_, false}->
-            lager:error("Dropped retained message(topic=~s, payload_size=~p) for payload is too big!", [Topic, size(Payload)])
+            lager:error("Cannot retain message(topic=~s, payload_size=~p)"
+                            " for payload is too big!", [Topic, size(Payload)])
     end, ok.
 
-limit(table) ->
-    proplists:get_value(max_message_num, env());
-limit(payload) ->
-    proplists:get_value(max_playload_size, env()).
+limit(table)   -> env(max_message_num);
+limit(payload) -> env(max_playload_size).
 
-env() -> 
-    case get({env, retained}) of
+env(Key) ->
+    case get({retained, Key}) of
         undefined ->
             Env = emqttd_broker:env(retained),
-            put({env, retained}, Env), Env;
-        Env -> 
-            Env
+            Val = proplists:get_value(Key, Env),
+            put({retained, Key}, Val), Val;
+        Val ->
+            Val
     end.
 
 %%%-----------------------------------------------------------------------------
@@ -124,3 +143,55 @@ dispatch(Topic, CPid) when is_binary(Topic) ->
     end,
     lists:foreach(fun(Msg) -> CPid ! {dispatch, Msg} end, lists:reverse(Msgs)).
 
+%%%=============================================================================
+%%% gen_server callbacks
+%%%=============================================================================
+
+init([]) ->
+    StatsFun = emqttd_stats:statsfun('retained/count', 'retained/max'),
+    {ok, #state{stats_fun     = StatsFun,
+                expired_after = env(expired_after),
+                stats_timer   = timer:send_interval(1000, stats),
+                expire_timer  = timer:send_interval(300 * 1000, expire)}}.
+
+handle_call(_Request, _From, State) ->
+    {reply, ok, State}.
+
+handle_cast(Msg, State) ->
+    lager:critical("Unexpected Msg: ~p", [Msg]),
+    {noreply, State}.
+
+handle_info(stats, State = #state{stats_fun = StatsFun}) ->
+    StatsFun(mnesia:table_info(retained, size)),
+    {noreply, State, hibernate};
+
+handle_info(expire, State = #state{expired_after = ExpiredAfter}) ->
+    expire(emqttd_util:now_to_secs(os:timestamp()) - ExpiredAfter),
+    {noreply, State, hibernate};
+
+handle_info(Info, State) ->
+    lager:critical("Unexpected Info: ~p", [Info]),
+    {noreply, State}.
+
+terminate(_Reason, _State = #state{stats_timer = TRef1, expire_timer = TRef2}) ->
+    timer:cancel(TRef1),
+    timer:cancel(TRef2).
+
+code_change(_OldVsn, State, _Extra) ->
+    {ok, State}.
+
+%%%=============================================================================
+%%% Internal functions
+%%%=============================================================================
+
+expire(Time) ->
+    mnesia:async_dirty(
+        fun() ->
+            Match = ets:fun2ms(
+                        fun(#mqtt_retained{topic = Topic, message = #mqtt_message{timestamp = {MegaSecs, Secs, _}}})
+                            when Time > (MegaSecs * 1000000 + Secs) -> Topic
+                        end),
+            Topics = mnesia:select(retained, Match, write),
+            lists:foreach(fun(Topic) -> mnesia:delete({retained, Topic}) end, Topics)
+        end).
+

src/emqttd_stats.erl

@@ -72,6 +72,11 @@
     'queues/max'         % ...
 ]).
 
+%% $SYS Topic for retained
+-define(SYSTOP_RETAINED, [
+    'retained/count',
+    'retained/max'
+]).
 
 %%%=============================================================================
 %%% API
@@ -139,7 +144,7 @@ setstats(Stat, MaxStat, Val) ->
 init([]) ->
     random:seed(now()),
     ets:new(?STATS_TAB, [set, public, named_table, {write_concurrency, true}]),
-    Topics = ?SYSTOP_CLIENTS ++ ?SYSTOP_SESSIONS ++ ?SYSTOP_PUBSUB,
+    Topics = ?SYSTOP_CLIENTS ++ ?SYSTOP_SESSIONS ++ ?SYSTOP_PUBSUB ++ ?SYSTOP_RETAINED,
     [ets:insert(?STATS_TAB, {Topic, 0}) || Topic <- Topics],
     % Create $SYS Topics
     [ok = emqttd_pubsub:create(stats_topic(Topic)) || Topic <- Topics],