122 lines
3.5 KiB
Erlang
122 lines
3.5 KiB
Erlang
%%--------------------------------------------------------------------
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%% Copyright (c) 2020-2022 EMQ Technologies Co., Ltd. All Rights Reserved.
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%%
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%% Licensed under the Apache License, Version 2.0 (the "License");
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%% you may not use this file except in compliance with the License.
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%% You may obtain a copy of the License at
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%%
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%% http://www.apache.org/licenses/LICENSE-2.0
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%%
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%% Unless required by applicable law or agreed to in writing, software
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%% distributed under the License is distributed on an "AS IS" BASIS,
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%% WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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%% See the License for the specific language governing permissions and
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%% limitations under the License.
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%%--------------------------------------------------------------------
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-module(emqx_exclusive_subscription).
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-include_lib("emqx/include/emqx.hrl").
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-include_lib("emqx/include/logger.hrl").
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-logger_header("[exclusive]").
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%% Mnesia bootstrap
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-export([mnesia/1]).
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-boot_mnesia({mnesia, [boot]}).
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-copy_mnesia({mnesia, [copy]}).
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%% For upgrade
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-export([on_add_module/0, on_delete_module/0]).
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-export([
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check_subscribe/2,
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unsubscribe/2
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]).
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-record(exclusive_subscription, {
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topic :: emqx_types:topic(),
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clientid :: emqx_types:clientid()
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}).
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-define(TAB, emqx_exclusive_subscription).
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%%--------------------------------------------------------------------
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%% Mnesia bootstrap
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%%--------------------------------------------------------------------
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mnesia(boot) ->
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StoreProps = [
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{ets, [
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{read_concurrency, true},
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{write_concurrency, true}
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]}
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],
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ok = ekka_mnesia:create_table(?TAB, [
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{type, set},
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{ram_copies, [node()]},
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{record_name, exclusive_subscription},
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{attributes, record_info(fields, exclusive_subscription)},
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{storage_properties, StoreProps}
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]);
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mnesia(copy) ->
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case ekka_mnesia:copy_table(?TAB, ram_copies) of
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ok ->
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ok;
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{no_exists, _} ->
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mnesia(boot)
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end.
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%%--------------------------------------------------------------------
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%% Upgrade
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%%--------------------------------------------------------------------
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on_add_module() ->
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mnesia(boot).
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on_delete_module() ->
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mnesia:clear_table(?TAB).
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%%--------------------------------------------------------------------
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%% APIs
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%%--------------------------------------------------------------------
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-spec check_subscribe(emqx_types:clientinfo(), emqx_types:topic()) ->
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allow | deny.
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check_subscribe(#{clientid := ClientId}, Topic) ->
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Fun = fun() ->
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try_subscribe(ClientId, Topic)
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end,
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case mnesia:transaction(Fun) of
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{atomic, Res} ->
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Res;
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{aborted, Reason} ->
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?LOG(warning, "Cannot check subscribe ~p due to ~p.", [Topic, Reason]),
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deny
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end.
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unsubscribe(Topic, #{is_exclusive := true}) ->
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_ = mnesia:transaction(fun() -> mnesia:delete({?TAB, Topic}) end),
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ok;
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unsubscribe(_Topic, _SubOpts) ->
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ok.
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%%--------------------------------------------------------------------
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%% Internal functions
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%%--------------------------------------------------------------------
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try_subscribe(ClientId, Topic) ->
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case mnesia:wread({?TAB, Topic}) of
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[] ->
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mnesia:write(
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?TAB,
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#exclusive_subscription{
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clientid = ClientId,
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topic = Topic
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},
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write
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),
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allow;
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[_] ->
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deny
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end.
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