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