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-module(rabbit_prelaunch_sighandler).
-behaviour(gen_event).
-export([setup/0,
init/1,
handle_event/2,
handle_call/2,
handle_info/2,
terminate/2,
code_change/3]).
%% CAUTION: Signal handling in this module must be kept consistent
%% with the same handling in rabbitmq-server(8).
%% #{signal => default | ignore | stop}.
-define(SIGNALS_HANDLED_BY_US,
#{
%% SIGHUP is often used to reload the configuration or reopen
%% log files after they were rotated. We don't support any
%% of those two cases, so ignore it for now, until we can do
%% something about it.
sighup => ignore,
%% SIGTSTP is triggered by Ctrl+Z to pause a program. However
%% we can't handle SIGCONT, the signal used to resume the
%% program. Unfortunately, it makes a SIGTSTP handler less
%% useful here.
sigtstp => ignore
}).
-define(SIGNAL_HANDLED_BY_ERLANG(Signal),
Signal =:= sigusr1 orelse
Signal =:= sigquit orelse
Signal =:= sigterm).
-define(SERVER, erl_signal_server).
setup() ->
case os:type() of
{unix, _} ->
case whereis(?SERVER) of
undefined ->
ok;
_ ->
case lists:member(?MODULE, gen_event:which_handlers(?SERVER)) of
true -> ok;
false -> gen_event:add_handler(?SERVER, ?MODULE, [])
end
end;
_ ->
ok
end.
init(_Args) ->
maps:fold(
fun
(Signal, _, Ret) when ?SIGNAL_HANDLED_BY_ERLANG(Signal) -> Ret;
(Signal, default, ok) -> os:set_signal(Signal, default);
(Signal, ignore, ok) -> os:set_signal(Signal, ignore);
(Signal, _, ok) -> os:set_signal(Signal, handle)
end, ok, ?SIGNALS_HANDLED_BY_US),
{ok, #{}}.
handle_event(Signal, State) when ?SIGNAL_HANDLED_BY_ERLANG(Signal) ->
{ok, State};
handle_event(Signal, State) ->
case ?SIGNALS_HANDLED_BY_US of
%% The code below can be uncommented if we introduce a signal
%% which should stop RabbitMQ.
%
%#{Signal := stop} ->
% error_logger:info_msg(
% "~s received - shutting down~n",
% [string:uppercase(atom_to_list(Signal))]),
% ok = init:stop();
_ ->
error_logger:info_msg(
"~s received - unhandled signal~n",
[string:uppercase(atom_to_list(Signal))])
end,
{ok, State}.
handle_info(_, State) ->
{ok, State}.
handle_call(_, State) ->
{ok, ok, State}.
code_change(_OldVsn, State, _Extra) ->
{ok, State}.
terminate(_Args, _State) ->
ok.
|
