APIs for hot reload of configuration

src/emqttd_config.erl

@@ -0,0 +1,59 @@
+%%--------------------------------------------------------------------
+%% Copyright (c) 2013-2017 EMQ Enterprise, Inc. (http://emqtt.io)
+%%
+%% Licensed under the Apache License, Version 2.0 (the "License");
+%% you may not use this file except in compliance with the License.
+%% You may obtain a copy of the License at
+%%
+%%     http://www.apache.org/licenses/LICENSE-2.0
+%%
+%% Unless required by applicable law or agreed to in writing, software
+%% distributed under the License is distributed on an "AS IS" BASIS,
+%% WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+%% See the License for the specific language governing permissions and
+%% limitations under the License.
+%%--------------------------------------------------------------------
+
+%% @doc Hot Configuration
+
+-module(emqttd_config).
+
+-export([read/1, dump/2, reload/1, get/2, get/3, set/3]).
+
+-type(env() :: {atom(), term()}).
+
+%% @doc Read the configuration of an application.
+-spec(read(atom()) -> {ok, list(env())} | {error, term()}).
+read(_App) ->
+    %% TODO
+    %% 1. Read the app.conf from etc folder
+    %% 2. Cuttlefish to read the conf
+    %% 3. Return the terms and schema
+    {error, unsupported}.
+
+%% @doc Reload configuration of an application.
+-spec(reload(atom()) -> ok | {error, term()}).
+reload(_App) ->
+    %% TODO
+    %% 1. Read the app.conf from etc folder
+    %% 2. Cuttlefish to generate config terms.
+    %% 3. set/3 to apply the config
+    ok.
+
+-spec(dump(atom(), list(env())) -> ok | {error, term()}).
+dump(_App, _Terms) ->
+    %% TODO
+    ok.
+
+-spec(set(atom(), atom(), term()) -> ok).
+set(App, Par, Val) ->
+    application:set_env(App, Par, Val).
+
+-spec(get(atom(), atom()) -> undefined | {ok, term()}).
+get(App, Par) ->
+    application:get_env(App, Par).
+
+-spec(get(atom(), atom(), atom()) -> term()).
+get(App, Par, Def) ->
+    application:get_env(App, Par, Def).
+