Implement graceful shutdown on interrupt or SIGTERM

cmd/signer/main.go

@@ -22,9 +22,13 @@ import (
 	"flag"
 	"fmt"
 	"os"
+	"os/signal"
+	"syscall"
 
 	"github.com/sirupsen/logrus"
 
+	"git.cacert.org/cacert-gosigner/pkg/protocol"
+
 	"git.cacert.org/cacert-gosigner/internal/config"
 	"git.cacert.org/cacert-gosigner/internal/handler"
 	"git.cacert.org/cacert-gosigner/internal/health"
@@ -83,6 +87,11 @@ func main() {
 		return
 	}
 
+	framer, err := protocol.NewCOBSFramer(logger)
+	if err != nil {
+		logger.WithError(err).Fatal("could not create framer")
+	}
+
 	healthHandler := health.New(version, access)
 
 	revokingRepositories, err := configureRepositories(caConfig, logger)
@@ -101,7 +110,7 @@ func main() {
 		logger.WithError(err).Fatal("could not setup protocol handler")
 	}
 
-	serialHandler, err := serial.New(caConfig.GetSerial(), logger, proto)
+	serialHandler, err := serial.New(caConfig.GetSerial(), logger, framer, proto)
 	if err != nil {
 		logger.WithError(err).Fatal("could not setup serial link handler")
 	}
@@ -110,11 +119,33 @@ func main() {
 
 	logger.Info("setup complete, starting signer operation")
 
-	if err = serialHandler.Run(context.Background()); err != nil {
-		logger.WithError(err).Fatal("error in serial handler")
+	if err = runSigner(logger, serialHandler); err != nil {
+		logger.WithError(err).Fatal("error running serial handler")
 	}
 }
 
+func runSigner(logger *logrus.Logger, serialHandler *serial.Handler) error {
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+
+	c := make(chan os.Signal, 1)
+	signal.Notify(c, os.Interrupt, syscall.SIGTERM)
+
+	go func() {
+		<-c
+
+		logger.Info("received shutdown signal")
+
+		cancel()
+	}()
+
+	if err := serialHandler.Run(ctx); err != nil {
+		return fmt.Errorf("error from serial handler: %w", err)
+	}
+
+	return nil
+}
+
 func configureRepositories(
 	caConfig *config.SignerConfig,
 	logger *logrus.Logger,

internal/serial/seriallink.go

@@ -21,6 +21,7 @@ package serial
 import (
 	"context"
 	"fmt"
+	"sync"
 
 	"github.com/sirupsen/logrus"
 	"github.com/tarm/serial"
@@ -60,26 +61,60 @@ func (h *Handler) Close() error {
 }
 
 func (h *Handler) Run(ctx context.Context) error {
+	const componentCount = 3
+
 	protocolErrors, framerErrors := make(chan error), make(chan error)
 
-	go func() {
-		err := h.framer.ReadFrames(ctx, h.port, h.framesIn)
+	subCtx, cancel := context.WithCancel(ctx)
+	wg := sync.WaitGroup{}
+	wg.Add(componentCount)
 
-		framerErrors <- err
+	defer func() {
+		cancel()
+		h.logger.Info("context canceled waiting for shutdown of components")
+		wg.Wait()
+		h.logger.Info("shutdown complete")
 	}()
 
 	go func() {
-		err := h.framer.WriteFrames(ctx, h.port, h.framesOut)
+		defer wg.Done()
 
-		framerErrors <- err
+		err := h.framer.ReadFrames(subCtx, h.port, h.framesIn)
+
+		h.logger.Info("frame reading stopped")
+
+		select {
+		case framerErrors <- err:
+		case <-subCtx.Done():
+		}
 	}()
 
 	go func() {
+		defer wg.Done()
+
+		err := h.framer.WriteFrames(subCtx, h.port, h.framesOut)
+
+		h.logger.Info("frame writing stopped")
+
+		select {
+		case framerErrors <- err:
+		case <-subCtx.Done():
+		}
+	}()
+
+	go func() {
+		defer wg.Done()
+
 		serverProtocol := protocol.NewServer(h.serverHandler, h.framesIn, h.framesOut, h.logger)
 
-		err := serverProtocol.Handle(ctx)
+		err := serverProtocol.Handle(subCtx)
 
-		protocolErrors <- err
+		h.logger.Info("server protocol stopped")
+
+		select {
+		case protocolErrors <- err:
+		case <-subCtx.Done():
+		}
 	}()
 
 	for {
@@ -105,23 +140,19 @@ func (h *Handler) Run(ctx context.Context) error {
 func New(
 	cfg *config.Serial,
 	logger *logrus.Logger,
+	framer protocol.Framer,
 	protocolHandler protocol.ServerHandler,
 ) (*Handler, error) {
-	cobsFramer, err := protocol.NewCOBSFramer(logger)
-	if err != nil {
-		return nil, fmt.Errorf("could not create COBS framer: %w", err)
-	}
-
 	h := &Handler{
 		serverHandler: protocolHandler,
 		logger:        logger,
 		framesIn:      make(chan []byte),
 		framesOut:     make(chan []byte),
-		framer:        cobsFramer,
+		framer:        framer,
 	}
 	h.config = &serial.Config{Name: cfg.Device, Baud: cfg.Baud, ReadTimeout: cfg.Timeout}
 
-	err = h.setupConnection()
+	err := h.setupConnection()
 	if err != nil {
 		return nil, err
 	}

pkg/protocol/protocol.go

@@ -421,7 +421,7 @@ func (c *COBSFramer) ReadFrames(ctx context.Context, reader io.Reader, frameChan
 		case <-ctx.Done():
 			return nil
 		default:
-			raw, err = c.readRaw(reader)
+			raw, err = c.readRaw(ctx, reader)
 			if err != nil {
 				close(frameChan)
 
@@ -469,21 +469,31 @@ func (c *COBSFramer) ReadFrames(ctx context.Context, reader io.Reader, frameChan
 	}
 }
 
-func (c *COBSFramer) readRaw(reader io.Reader) ([]byte, error) {
-	buf := make([]byte, bufferSize)
+func (c *COBSFramer) readRaw(ctx context.Context, reader io.Reader) ([]byte, error) {
+	result := make(chan []byte)
+	errChan := make(chan error)
 
-	count, err := reader.Read(buf)
-	if err != nil {
-		if errors.Is(err, io.EOF) {
-			return buf[:count], nil
+	go func() {
+		buf := make([]byte, bufferSize)
+
+		count, err := reader.Read(buf)
+		if err != nil {
+			if !errors.Is(err, io.EOF) {
+				errChan <- fmt.Errorf("could not read data: %w", err)
+			}
 		}
 
-		return nil, fmt.Errorf("could not read data: %w", err)
+		result <- buf[:count]
+	}()
+
+	select {
+	case <-ctx.Done():
+		return nil, nil
+	case raw := <-result:
+		return raw, nil
+	case err := <-errChan:
+		return nil, err
 	}
-
-	raw := buf[:count]
-
-	return raw, nil
 }
 
 func (c *COBSFramer) WriteFrames(ctx context.Context, writer io.Writer, frameChan chan []byte) error {