shimv2: handle sigint/sigterm

This causes sigint/sigterm to trigger a shutdown of the shim.
It is needed because otherwise the v2 shim hangs system shutdown.

Signed-off-by: Brian Goff <cpuguy83@gmail.com>
(cherry picked from commit 3ffb6a6)
Signed-off-by: Varsha Teratipally <teratipally@google.com>

runtime/v2/shim/shim.go

@@ -214,7 +214,7 @@ func run(id string, initFunc Init, config Config) error {
 			"pid":       os.Getpid(),
 			"namespace": namespaceFlag,
 		})
-		go handleSignals(ctx, logger, signals)
+		go reap(ctx, logger, signals)
 		response, err := service.Cleanup(ctx)
 		if err != nil {
 			return err
@@ -310,7 +310,9 @@ func (s *Client) Serve() error {
 			dumpStacks(logger)
 		}
 	}()
-	return handleSignals(s.context, logger, s.signals)
+	ctx, cancel := context.WithCancel(s.context)
+	go handleExitSignals(ctx, logger, cancel)
+	return reap(ctx, logger, s.signals)
 }
 
 // serve serves the ttrpc API over a unix socket at the provided path

runtime/v2/shim/shim_unix.go

@@ -70,14 +70,16 @@ func serveListener(path string) (net.Listener, error) {
 	return l, nil
 }
 
-func handleSignals(ctx context.Context, logger *logrus.Entry, signals chan os.Signal) error {
+func reap(ctx context.Context, logger *logrus.Entry, signals chan os.Signal) error {
 	logger.Info("starting signal loop")
 
 	for {
 		select {
 		case <-ctx.Done():
 			return ctx.Err()
 		case s := <-signals:
+			// Exit signals are handled separately from this loop
+			// They get registered with this channel so that we can ignore such signals for short-running actions (e.g. `delete`)
 			switch s {
 			case unix.SIGCHLD:
 				if err := reaper.Reap(); err != nil {
@@ -89,6 +91,22 @@ func handleSignals(ctx context.Context, logger *logrus.Entry, signals chan os.Si
 	}
 }
 
+func handleExitSignals(ctx context.Context, logger *logrus.Entry, cancel context.CancelFunc) {
+	ch := make(chan os.Signal, 32)
+	signal.Notify(ch, syscall.SIGINT, syscall.SIGTERM)
+
+	for {
+		select {
+		case s := <-ch:
+			logger.WithField("signal", s).Debugf("Caught exit signal")
+			cancel()
+			return
+		case <-ctx.Done():
+			return
+		}
+	}
+}
+
 func openLog(ctx context.Context, _ string) (io.Writer, error) {
 	return fifo.OpenFifoDup2(ctx, "log", unix.O_WRONLY, 0700, int(os.Stderr.Fd()))
 }

runtime/v2/shim/shim_windows.go

@@ -48,10 +48,13 @@ func serveListener(path string) (net.Listener, error) {
 	return nil, errors.New("not supported")
 }
 
-func handleSignals(ctx context.Context, logger *logrus.Entry, signals chan os.Signal) error {
+func reap(ctx context.Context, logger *logrus.Entry, signals chan os.Signal) error {
 	return errors.New("not supported")
 }
 
+func handleExitSignals(ctx context.Context, logger *logrus.Entry, cancel context.CancelFunc) {
+}
+
 func openLog(ctx context.Context, _ string) (io.Writer, error) {
 	return nil, errors.New("not supported")
 }