%%%----------------------------------------------------------------------
%%% File : ejabberd_systemd.erl
%%% Author : Holger Weiss <holger@zedat.fu-berlin.de>
%%% Purpose : Integrate with systemd
%%% Created : 5 Jan 2021 by Holger Weiss <holger@zedat.fu-berlin.de>
%%%
%%%
%%% ejabberd, Copyright (C) 2021 ProcessOne
%%%
%%% This program is free software; you can redistribute it and/or
%%% modify it under the terms of the GNU General Public License as
%%% published by the Free Software Foundation; either version 2 of the
%%% License, or (at your option) any later version.
%%%
%%% This program is distributed in the hope that it will be useful,
%%% but WITHOUT ANY WARRANTY; without even the implied warranty of
%%% MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
%%% General Public License for more details.
%%%
%%% You should have received a copy of the GNU General Public License along
%%% with this program; if not, write to the Free Software Foundation, Inc.,
%%% 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
%%%
%%%----------------------------------------------------------------------
-module(ejabberd_systemd).
-author('holger@zedat.fu-berlin.de').
-behaviour(gen_server).
-export([start_link/0,
ready/0,
reloading/0,
stopping/0]).
-export([init/1,
handle_call/3,
handle_cast/2,
handle_info/2,
terminate/2,
code_change/3]).
-include("logger.hrl").
-record(state,
{socket :: gen_udp:socket() | undefined,
destination :: inet:local_address() | undefined,
interval :: pos_integer() | undefined,
last_ping :: integer() | undefined}).
-type watchdog_timeout() :: pos_integer() | hibernate.
-type state() :: #state{}.
%%--------------------------------------------------------------------
%% API.
%%--------------------------------------------------------------------
-spec start_link() -> {ok, pid()} | ignore | {error, term()}.
start_link() ->
gen_server:start_link({local, ?MODULE}, ?MODULE, [], []).
-spec ready() -> ok.
ready() ->
cast_notification(<<"READY=1">>).
-spec reloading() -> ok.
reloading() ->
cast_notification(<<"RELOADING=1">>).
-spec stopping() -> ok.
stopping() ->
cast_notification(<<"STOPPING=1">>).
%%--------------------------------------------------------------------
%% gen_server callbacks.
%%--------------------------------------------------------------------
-spec init(any())
-> {ok, state()} | {ok, state(), watchdog_timeout()} | {stop, term()}.
init(_Opts) ->
process_flag(trap_exit, true),
case os:getenv("NOTIFY_SOCKET") of
[$@ | _Abstract] ->
?CRITICAL_MSG("Abstract NOTIFY_SOCKET not supported", []),
{stop, esocktnosupport};
Path when is_list(Path), length(Path) > 0 ->
?DEBUG("Got NOTIFY_SOCKET: ~s", [Path]),
Destination = {local, Path},
case gen_udp:open(0, [local]) of
{ok, Socket} ->
Interval = get_watchdog_interval(),
State = #state{socket = Socket,
destination = Destination,
interval = Interval},
if is_integer(Interval), Interval > 0 ->
?INFO_MSG("Watchdog notifications enabled", []),
{ok, set_last_ping(State), Interval};
true ->
?INFO_MSG("Watchdog notifications disabled", []),
{ok, State}
end;
{error, Reason} ->
?CRITICAL_MSG("Cannot open IPC socket: ~p", [Reason]),
{stop, Reason}
end;
_ ->
?INFO_MSG("Got no NOTIFY_SOCKET, notifications disabled", []),
{ok, #state{}}
end.
-spec handle_call(term(), {pid(), term()}, state())
-> {reply, {error, badarg}, state(), watchdog_timeout()}.
handle_call(Request, From, State) ->
?ERROR_MSG("Got unexpected request from ~p: ~p", [From, Request]),
{reply, {error, badarg}, State, get_timeout(State)}.
-spec handle_cast({notify, binary()} | term(), state())
-> {noreply, state(), watchdog_timeout()}.
handle_cast({notify, Notification},
#state{destination = undefined} = State) ->
?DEBUG("No NOTIFY_SOCKET, dropping ~s notification", [Notification]),
{noreply, State, get_timeout(State)};
handle_cast({notify, Notification}, State) ->
try notify(State, Notification)
catch _:Err ->
?ERROR_MSG("Cannot send ~s notification: ~p", [Notification, Err])
end,
{noreply, State, get_timeout(State)};
handle_cast(Msg, State) ->
?ERROR_MSG("Got unexpected message: ~p", [Msg]),
{noreply, State, get_timeout(State)}.
-spec handle_info(timeout | term(), state())
-> {noreply, state(), watchdog_timeout()}.
handle_info(timeout, #state{interval = Interval} = State)
when is_integer(Interval), Interval > 0 ->
try notify(State, <<"WATCHDOG=1">>)
catch _:Err ->
?ERROR_MSG("Cannot ping watchdog: ~p", [Err])
end,
{noreply, set_last_ping(State), Interval};
handle_info(Info, State) ->
?ERROR_MSG("Got unexpected info: ~p", [Info]),
{noreply, State, get_timeout(State)}.
-spec terminate(normal | shutdown | {shutdown, term()} | term(), state()) -> ok.
terminate(Reason, #state{socket = undefined}) ->
?DEBUG("Terminating ~s (~p)", [?MODULE, Reason]),
ok;
terminate(Reason, #state{socket = Socket}) ->
?DEBUG("Closing socket and terminating ~s (~p)", [?MODULE, Reason]),
ok = gen_udp:close(Socket).
-spec code_change({down, term()} | term(), state(), term()) -> {ok, state()}.
code_change(_OldVsn, State, _Extra) ->
?INFO_MSG("Got code change request", []),
{ok, State}.
%%--------------------------------------------------------------------
%% Internal functions.
%%--------------------------------------------------------------------
-spec get_watchdog_interval() -> integer() | undefined.
get_watchdog_interval() ->
case os:getenv("WATCHDOG_USEC") of
WatchdogUSec when is_list(WatchdogUSec), length(WatchdogUSec) > 0 ->
Interval = round(0.5 * list_to_integer(WatchdogUSec)),
?DEBUG("Watchdog interval: ~B microseconds", [Interval]),
erlang:convert_time_unit(Interval, microsecond, millisecond);
_ ->
undefined
end.
-spec get_timeout(state()) -> watchdog_timeout().
get_timeout(#state{interval = undefined}) ->
?DEBUG("Watchdog interval is undefined, hibernating", []),
hibernate;
get_timeout(#state{interval = Interval, last_ping = LastPing}) ->
case Interval - (erlang:monotonic_time(millisecond) - LastPing) of
Timeout when Timeout > 0 ->
?DEBUG("Calculated new timeout value: ~B", [Timeout]),
Timeout;
_ ->
?DEBUG("Calculated new timeout value: 1", []),
1
end.
-spec set_last_ping(state()) -> state().
set_last_ping(State) ->
LastPing = erlang:monotonic_time(millisecond),
State#state{last_ping = LastPing}.
-spec notify(state(), binary()) -> ok.
notify(#state{socket = Socket, destination = Destination},
Notification) ->
?DEBUG("Notifying systemd: ~s", [Notification]),
ok = gen_udp:send(Socket, Destination, 0, Notification).
-spec cast_notification(binary()) -> ok.
cast_notification(Notification) ->
gen_server:cast(?MODULE, {notify, Notification}).
