Merge pull request #2244 from rabbitmq/only-handle-SIGHUP-and-SIGTSTP

Only handle SIGHUP and SIGTSTP

2 files changed, 88 insertions, 0 deletions

diff --git a/apps/rabbitmq_prelaunch/src/rabbit_prelaunch.erl b/apps/rabbitmq_prelaunch/src/rabbit_prelaunch.erl
index b564fadf51..ef15f47a75 100644
--- a/apps/rabbitmq_prelaunch/src/rabbit_prelaunch.erl
+++ b/apps/rabbitmq_prelaunch/src/rabbit_prelaunch.erl
@@ -48,6 +48,9 @@ do_run() ->
     %% Configure dbg if requested.
     rabbit_prelaunch_early_logging:enable_quick_dbg(rabbit_env:dbg_config()),
 
+    %% Setup signal handler.
+    ok = rabbit_prelaunch_sighandler:setup(),
+
     %% We assert Mnesia is stopped before we run the prelaunch
     %% phases.
     %%
diff --git a/apps/rabbitmq_prelaunch/src/rabbit_prelaunch_sighandler.erl b/apps/rabbitmq_prelaunch/src/rabbit_prelaunch_sighandler.erl
new file mode 100644
index 0000000000..a6b5d3c2f7
--- /dev/null
+++ b/apps/rabbitmq_prelaunch/src/rabbit_prelaunch_sighandler.erl
@@ -0,0 +1,85 @@
+-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 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.
+
+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
+        #{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.