systemd

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%%
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%% under the License.
%%
%% @private

-module(systemd_sup).

-behaviour(supervisor).

-include("systemd_internal.hrl").

-export([start_link/1, init/1]).

-include_lib("kernel/include/file.hrl").

start_link(Opts) ->
    supervisor:start_link({local, ?SUPERVISOR}, ?MODULE, Opts).

init(_Opts) ->
    SupFlags = #{
        strategy => one_for_one
    },
    SocketServer = #{
        id => socket,
        start => {systemd_socket, start_link, [notify_socket()]}
    },

    WatchdogConfig = watchdog(),
    Watchdog = #{
        id => watchdog,
        start => {systemd_watchdog, start_link, [WatchdogConfig]}
    },

    {ok, {SupFlags, [SocketServer, Watchdog]}}.

watchdog() ->
    Pid = os:getpid(),
    Enabled =
        case os:getenv(?WATCHDOG_PID) of
            false -> true;
            Pid -> true;
            _ -> false
        end,
    Time =
        case os:getenv(?WATCHDOG_TIMEOUT) of
            false ->
                infinity;
            EnvTime ->
                case string:to_integer(EnvTime) of
                    {Timeout, ""} when Timeout > 0 ->
                        erlang:convert_time_unit(
                            Timeout,
                            microsecond,
                            millisecond
                        );
                    _ ->
                        infinity
                end
        end,
    unset(watchdog),
    case {Enabled, Time} of
        {_, infinity} -> {false, infinity};
        Other -> Other
    end.

notify_socket() ->
    State =
        case os:getenv(?NOTIFY_SOCKET) of
            false ->
                [];
            [$@ | AbstractPath] ->
                [0 | AbstractPath];
            Path ->
                case file:read_file_info(Path) of
                    {error, _Error} ->
                        [];
                    {ok, #file_info{access = Access}} when
                        Access =:= write; Access =:= read_write
                    ->
                        Path
                end
        end,
    unset(notify),
    State.

unset(System) ->
    {ok, Unset} = application:get_env(systemd, unset_env),
    unset(System, Unset).

unset(System, true) -> systemd:unset_env(System);
unset(_System, _) -> ok.