add wheel

apps/sdlan/include/dns_proxy.hrl

@@ -8,6 +8,9 @@
 %%%-------------------------------------------------------------------
 -author("anlicheng").
 
+-define(PENDING_TAB, ets_dns_pending_queries).
+-define(PENDING_INDEX_TAB, ets_dns_expire_index).
+
 -record(dns_cache, {
     %% {Qname, QType, QClass}
     key,

apps/sdlan/src/dns_proxy/dns_pending_wheel.erl

@@ -0,0 +1,69 @@
+-module(dns_pending_wheel).
+
+-export([start/0, put/2, get/1, delete/1]).
+
+-define(TTL, 5).
+-define(TICK_MS, 1000).
+-define(WHEEL_SIZE, (?TTL + 1)).
+
+%%% =====================================================
+%%% Public API
+%%% =====================================================
+
+start() ->
+    ets:new(dns_pending_data, [ordered_set, public, named_table]),
+    ets:new(dns_pending_wheel, [bag, public, named_table]),
+    start_scanner().
+
+-spec put(Key :: any(), Val :: any()) -> ok.
+put(Key, Val) ->
+    Tick = now_tick(),
+    Slot = Tick rem ?WHEEL_SIZE,
+    ets:insert(dns_pending_data, {Key, {Val, Tick}}),
+    ets:insert(dns_pending_wheel, {Slot, {Key, Tick}}),
+    ok.
+
+-spec get(Key :: any()) -> error | {ok, Val :: any()}.
+get(Key) ->
+    case ets:lookup(dns_pending_data, Key) of
+        [{Key, {Val, _Tick}}] ->
+            {ok, Val};
+        [] ->
+            error
+    end.
+
+-spec delete(Key :: any()) -> ok.
+delete(Key) ->
+    ets:delete(dns_pending_data, Key),
+    ok.
+
+%%% =====================================================
+%%% Internal
+%%% =====================================================
+
+start_scanner() ->
+    {ok, spawn_link(fun tick_loop/0)}.
+
+%% 当前插入数据是在Tick, 而清理是从 Tick + 1 开始的，没有问题
+tick_loop() ->
+    Tick = now_tick(),
+    CleanSlot = (Tick + 1) rem ?WHEEL_SIZE,
+    spawn(fun() -> clean_slot(CleanSlot) end),
+    timer:sleep(?TICK_MS),
+    tick_loop().
+
+clean_slot(Slot) ->
+    Items = ets:lookup(dns_pending_wheel, Slot),
+    true = ets:delete(dns_pending_wheel, Slot),
+    lists:foreach(fun({_, {Key, InsertTick}}) ->
+        case ets:lookup(dns_pending_data, Key) of
+            [{Key, {_Val, InsertTick}}] ->
+                ets:delete(dns_pending_data, Key);
+            _ ->
+                ok
+        end
+                  end, Items).
+
+-spec now_tick() -> integer().
+now_tick() ->
+    erlang:system_time(second).

apps/sdlan/src/sdlan_app.erl

@@ -19,6 +19,7 @@ start(_StartType, _StartArgs) ->
     %% 启动注册表
     sdlan_hostname_regedit:init(),
     sdlan_domain_regedit:init(),
+    dns_pending_wheel:start(),
 
     start_http_server(),
     start_tcp_server(),