shimv2: handle sigint/sigterm

cpuguy83 · cpuguy83 · commit 3ffb6a611302 · 2022-01-25T17:57:28.000Z
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 &lt;cpuguy83@gmail.com&gt;
diff --git a/runtime/v2/shim/shim.go b/runtime/v2/shim/shim.go
@@ -305,7 +305,7 @@ func run(ctx context.Context, manager Manager, initFunc Init, name string, confi
 			"pid":       os.Getpid(),
 			"namespace": namespaceFlag,
 		})
-		go handleSignals(ctx, logger, signals)
+		go reap(ctx, logger, signals)
 		ss, err := manager.Stop(ctx, id)
 		if err != nil {
 			return err
@@ -428,7 +428,7 @@ func run(ctx context.Context, manager Manager, initFunc Init, name string, confi
 		}
 	}
 
-	if err := serve(ctx, server, signals); err != nil {
+	if err := serve(ctx, server, signals, sd.Shutdown); err != nil {
 		if err != shutdown.ErrShutdown {
 			return err
 		}
@@ -450,7 +450,7 @@ func run(ctx context.Context, manager Manager, initFunc Init, name string, confi
 
 // serve serves the ttrpc API over a unix socket in the current working directory
 // and blocks until the context is canceled
-func serve(ctx context.Context, server *ttrpc.Server, signals chan os.Signal) error {
+func serve(ctx context.Context, server *ttrpc.Server, signals chan os.Signal, shutdown func()) error {
 	dump := make(chan os.Signal, 32)
 	setupDumpStacks(dump)
 
@@ -480,7 +480,9 @@ func serve(ctx context.Context, server *ttrpc.Server, signals chan os.Signal) er
 			dumpStacks(logger)
 		}
 	}()
-	return handleSignals(ctx, logger, signals)
+
+	go handleExitSignals(ctx, logger, shutdown)
+	return reap(ctx, logger, signals)
 }
 
 func dumpStacks(logger *logrus.Entry) {
diff --git a/runtime/v2/shim/shim_unix.go b/runtime/v2/shim/shim_unix.go
@@ -71,14 +71,16 @@ 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 {
@@ -90,6 +92,22 @@ 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()))
 }
diff --git a/runtime/v2/shim/shim_windows.go b/runtime/v2/shim/shim_windows.go
@@ -46,10 +46,13 @@ 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")
 }

Original file line number	Diff line number	Diff line change
`@@ -46,10 +46,13 @@ func serveListener(path string) (net.Listener, error) {`
`46`	`46`	`return nil, errors.New("not supported")`
`47`	`47`	`}`
`48`	`48`
`49`		`-func handleSignals(ctx context.Context, logger *logrus.Entry, signals chan os.Signal) error {`
	`49`	`+func reap(ctx context.Context, logger *logrus.Entry, signals chan os.Signal) error {`
`50`	`50`	`return errors.New("not supported")`
`51`	`51`	`}`
`52`	`52`
	`53`	`+func handleExitSignals(ctx context.Context, logger *logrus.Entry, cancel context.CancelFunc) {`
	`54`	`+}`
	`55`	`+`
`53`	`56`	`func openLog(ctx context.Context, _ string) (io.Writer, error) {`
`54`	`57`	`return nil, errors.New("not supported")`
`55`	`58`	`}`