refactor: delete module emqx_license_installer

after the previous refactoring, emqx_license app is now restarted
after join/rejoin the cluster, so there is no longer a need for the
installer process which monitors the 'emqx' name registration changes
and then issue license reloading and hook re-adding etc.

lib-ee/emqx_license/src/emqx_license_installer.erl

@@ -1,86 +0,0 @@
-%%--------------------------------------------------------------------
-%% Copyright (c) 2022-2023 EMQ Technologies Co., Ltd. All Rights Reserved.
-%%--------------------------------------------------------------------
--module(emqx_license_installer).
-
--include_lib("snabbkaffe/include/snabbkaffe.hrl").
-
--behaviour(gen_server).
-
--export([
-    start_link/1,
-    start_link/4
-]).
-
-%% gen_server callbacks
--export([
-    init/1,
-    handle_call/3,
-    handle_cast/2,
-    handle_info/2
-]).
-
--define(NAME, emqx).
--define(INTERVAL, 5000).
-
-%%------------------------------------------------------------------------------
-%% API
-%%------------------------------------------------------------------------------
-
-start_link(Callback) ->
-    start_link(?NAME, ?MODULE, ?INTERVAL, Callback).
-
-start_link(Name, ServerName, Interval, Callback) ->
-    gen_server:start_link({local, ServerName}, ?MODULE, [Name, Interval, Callback], []).
-
-%%------------------------------------------------------------------------------
-%% gen_server callbacks
-%%------------------------------------------------------------------------------
-
-init([Name, Interval, Callback]) ->
-    Pid = whereis(Name),
-    State = #{
-        interval => Interval,
-        name => Name,
-        pid => Pid,
-        callback => Callback
-    },
-    {ok, ensure_timer(State)}.
-
-handle_call(_Req, _From, State) ->
-    {reply, unknown, State}.
-
-handle_cast(_Msg, State) ->
-    {noreply, State}.
-
-handle_info({timeout, Timer, check_pid}, #{timer := Timer} = State) ->
-    NewState = check_pid(State),
-    {noreply, ensure_timer(NewState)};
-handle_info(_Msg, State) ->
-    {noreply, State}.
-
-%%------------------------------------------------------------------------------
-%% Private functions
-%%------------------------------------------------------------------------------
-
-ensure_timer(#{interval := Interval} = State) ->
-    _ =
-        case State of
-            #{timer := Timer} -> erlang:cancel_timer(Timer);
-            _ -> ok
-        end,
-    State#{timer => erlang:start_timer(Interval, self(), check_pid)}.
-
-check_pid(#{name := Name, pid := OldPid, callback := Callback} = State) ->
-    case whereis(Name) of
-        undefined ->
-            ?tp(emqx_license_installer_noproc, #{old_pid => OldPid}),
-            State;
-        OldPid ->
-            ?tp(emqx_license_installer_nochange, #{old_pid => OldPid}),
-            State;
-        NewPid ->
-            _ = Callback(),
-            ?tp(info, license_reloaded_after_emqx_app_restart, #{old_pid => OldPid}),
-            State#{pid => NewPid}
-    end.

lib-ee/emqx_license/src/emqx_license_sup.erl

@@ -41,15 +41,6 @@ init([]) ->
                     shutdown => 5000,
                     type => worker,
                     modules => [emqx_license_resources]
-                },
-
-                #{
-                    id => license_installer,
-                    start => {emqx_license_installer, start_link, [fun emqx_license:load/0]},
-                    restart => permanent,
-                    shutdown => 5000,
-                    type => worker,
-                    modules => [emqx_license_installer]
                 }
             ]
         }}.

lib-ee/emqx_license/test/emqx_license_installer_SUITE.erl

@@ -1,89 +0,0 @@
-%%--------------------------------------------------------------------
-%% Copyright (c) 2022-2023 EMQ Technologies Co., Ltd. All Rights Reserved.
-%%--------------------------------------------------------------------
-
--module(emqx_license_installer_SUITE).
-
--compile(nowarn_export_all).
--compile(export_all).
-
--include_lib("eunit/include/eunit.hrl").
--include_lib("common_test/include/ct.hrl").
--include_lib("snabbkaffe/include/snabbkaffe.hrl").
-
-all() ->
-    emqx_common_test_helpers:all(?MODULE).
-
-init_per_suite(Config) ->
-    _ = application:load(emqx_conf),
-    emqx_common_test_helpers:start_apps([emqx_license], fun set_special_configs/1),
-    Config.
-
-end_per_suite(_) ->
-    emqx_common_test_helpers:stop_apps([emqx_license]),
-    ok.
-
-init_per_testcase(_Case, Config) ->
-    {ok, _} = emqx_cluster_rpc:start_link(node(), emqx_cluster_rpc, 1000),
-    Config.
-
-end_per_testcase(_Case, _Config) ->
-    ok.
-
-set_special_configs(emqx_license) ->
-    Config = #{key => emqx_license_test_lib:default_license()},
-    emqx_config:put([license], Config);
-set_special_configs(_) ->
-    ok.
-
-%%------------------------------------------------------------------------------
-%% Tests
-%%------------------------------------------------------------------------------
-
-t_update(_Config) ->
-    ?check_trace(
-        begin
-            ?wait_async_action(
-                begin
-                    Pid0 = spawn_link(fun() ->
-                        receive
-                            exit -> ok
-                        end
-                    end),
-                    register(installer_test, Pid0),
-
-                    {ok, _} = emqx_license_installer:start_link(
-                        installer_test,
-                        ?MODULE,
-                        10,
-                        fun() -> ok end
-                    ),
-
-                    {ok, _} = ?block_until(
-                        #{?snk_kind := emqx_license_installer_nochange},
-                        100
-                    ),
-
-                    Pid0 ! exit,
-
-                    {ok, _} = ?block_until(
-                        #{?snk_kind := emqx_license_installer_noproc},
-                        100
-                    ),
-
-                    Pid1 = spawn_link(fun() -> timer:sleep(100) end),
-                    register(installer_test, Pid1)
-                end,
-                #{?snk_kind := license_reloaded_after_emqx_app_restart},
-                1000
-            )
-        end,
-        fun(Trace) ->
-            ?assertMatch([_ | _], ?of_kind(license_reloaded_after_emqx_app_restart, Trace))
-        end
-    ).
-
-t_unknown_calls(_Config) ->
-    ok = gen_server:cast(emqx_license_installer, some_cast),
-    some_msg = erlang:send(emqx_license_installer, some_msg),
-    ?assertEqual(unknown, gen_server:call(emqx_license_installer, some_request)).