Try to limit serial access when checking api permissions

src/ejabberd_access_permissions.erl

@@ -46,6 +46,7 @@
 	 code_change/3]).
 
 -define(SERVER, ?MODULE).
+-define(CACHE_TAB, access_permissions_cache).
 
 -record(state,
 	{definitions = none :: none | [definition()]}).
@@ -71,35 +72,10 @@
 %%%===================================================================
 -spec can_access(atom(), caller_info()) -> allow | deny.
 can_access(Cmd, CallerInfo) ->
-    gen_server:call(?MODULE, {can_access, Cmd, CallerInfo}).
+    Defs0 = show_current_definitions(),
-
--spec invalidate() -> ok.
-invalidate() ->
-    gen_server:cast(?MODULE, invalidate).
-
--spec show_current_definitions() -> [definition()].
-show_current_definitions() ->
-    gen_server:call(?MODULE, show_current_definitions).
-
-start_link() ->
-    gen_server:start_link({local, ?SERVER}, ?MODULE, [], []).
-
-%%%===================================================================
-%%% gen_server callbacks
-%%%===================================================================
--spec init([]) -> {ok, state()}.
-init([]) ->
-    ejabberd_hooks:add(config_reloaded, ?MODULE, invalidate, 90),
-    {ok, #state{}}.
-
--spec handle_call({can_access, atom(), caller_info()} |
-		  show_current_definitions | term(),
-		  term(), state()) -> {reply, term(), state()}.
-handle_call({can_access, Cmd, CallerInfo}, _From, State) ->
     CallerModule = maps:get(caller_module, CallerInfo, none),
     Host = maps:get(caller_host, CallerInfo, global),
     Tag = maps:get(tag, CallerInfo, none),
-    {State2, Defs0} = get_definitions(State),
     Defs = maps:get(extra_permissions, CallerInfo, []) ++ Defs0,
     Res = lists:foldl(
 	fun({Name, _} = Def, none) ->
@@ -114,14 +90,40 @@ handle_call({can_access, Cmd, CallerInfo}, _From, State) ->
 	   (_, Val) ->
 	       Val
 	end, none, Defs),
-    Res2 = case Res of
+    case Res of
 	allow -> allow;
 	_ ->
 	    ?DEBUG("Command '~p' execution denied "
 		   "(CallerInfo=~p)", [Cmd, CallerInfo]),
 	    deny
-	   end,
+    end.
-    {reply, Res2, State2};
+
+-spec invalidate() -> ok.
+invalidate() ->
+    gen_server:cast(?MODULE, invalidate),
+    ets_cache:delete(?CACHE_TAB, definitions).
+
+-spec show_current_definitions() -> [definition()].
+show_current_definitions() ->
+    ets_cache:lookup(?CACHE_TAB, definitions,
+		     fun() ->
+			 {cache, gen_server:call(?MODULE, show_current_definitions)}
+		     end).
+start_link() ->
+    ets_cache:new(?CACHE_TAB, [{max_size, 2}]),
+    gen_server:start_link({local, ?SERVER}, ?MODULE, [], []).
+
+%%%===================================================================
+%%% gen_server callbacks
+%%%===================================================================
+-spec init([]) -> {ok, state()}.
+init([]) ->
+    ejabberd_hooks:add(config_reloaded, ?MODULE, invalidate, 90),
+    ets_cache:new(access_permissions),
+    {ok, #state{}}.
+
+-spec handle_call(show_current_definitions | term(),
+		  term(), state()) -> {reply, term(), state()}.
 handle_call(show_current_definitions, _From, State) ->
     {State2, Defs} = get_definitions(State),
     {reply, Defs, State2};