GODT-2039: bridge monitors bridge-gui via its PID.

internal/frontend/grpc/service.go

@@ -40,6 +40,9 @@ import (
 	"github.com/ProtonMail/proton-bridge/v2/pkg/keychain"
 	"github.com/ProtonMail/proton-bridge/v2/pkg/listener"
 	"github.com/ProtonMail/proton-bridge/v2/pkg/pmapi"
+	"github.com/bradenaw/juniper/xslices"
+	"github.com/elastic/go-sysinfo"
+	sysinfotypes "github.com/elastic/go-sysinfo/types"
 	"github.com/google/uuid"
 	"github.com/pkg/errors"
 	"github.com/sirupsen/logrus"
@@ -85,6 +88,8 @@ type Service struct { // nolint:structcheck
 	locations          *locations.Locations
 	token              string
 	pemCert            string
+	parentPID          int
+	parentPIDDoneCh    chan struct{}
 }
 
 // NewService returns a new instance of the service.
@@ -95,6 +100,7 @@ func NewService(
 	updater types.Updater,
 	restarter types.Restarter,
 	locations *locations.Locations,
+	parentPID int,
 ) *Service {
 	s := Service{
 		UnimplementedBridgeServer: UnimplementedBridgeServer{},
@@ -110,6 +116,8 @@ func NewService(
 		firstTimeAutostart: sync.Once{},
 		locations:          locations,
 		token:              uuid.NewString(),
+		parentPID:          parentPID,
+		parentPIDDoneCh:    make(chan struct{}),
 	}
 
 	// Initializing.Done is only called sync.Once. Please keep the increment
@@ -177,6 +185,12 @@ func (s *Service) Loop(b types.Bridger) error {
 	s.initAutostart()
 	s.startGRPCServer()
 
+	if s.parentPID < 0 {
+		s.log.Info("Not monitoring parent PID")
+	} else {
+		go s.monitorParentPID()
+	}
+
 	defer func() {
 		s.bridge.SetBool(settings.FirstStartGUIKey, false)
 	}()
@@ -520,3 +534,36 @@ func (s *Service) validateStreamServerToken(
 
 	return handler(srv, ss)
 }
+
+// monitorParentPID check at regular intervals that the parent process is still alive, and if not shuts down the server
+// and the applications.
+func (s *Service) monitorParentPID() {
+	s.log.Infof("Starting to monitor parent PID %v", s.parentPID)
+	ticker := time.NewTicker(5 * time.Second)
+
+	for {
+		select {
+		case <-ticker.C:
+			if s.parentPID < 0 {
+				continue
+			}
+
+			processes, err := sysinfo.Processes() // sysinfo.Process(pid) does not seem to work on Windows.
+			if err != nil {
+				s.log.Debug("Could not retrieve process list")
+				continue
+			}
+
+			if !xslices.Any(processes, func(p sysinfotypes.Process) bool { return p != nil && p.PID() == s.parentPID }) {
+				s.log.Info("Parent process does not exist anymore. Initiating shutdown")
+				go s.quit() // quit will write to the parentPIDDoneCh, so we launch a goroutine.
+			} else {
+				s.log.Tracef("Parent process %v is still alive", s.parentPID)
+			}
+
+		case <-s.parentPIDDoneCh:
+			s.log.Infof("Stopping process monitoring for PID %v", s.parentPID)
+			return
+		}
+	}
+}

internal/frontend/grpc/service_methods.go

@@ -95,15 +95,19 @@ func (s *Service) GuiReady(ctx context.Context, _ *emptypb.Empty) (*emptypb.Empt
 // Quit implement the Quit gRPC service call.
 func (s *Service) Quit(ctx context.Context, empty *emptypb.Empty) (*emptypb.Empty, error) {
 	s.log.Debug("Quit")
-	return &emptypb.Empty{}, s.quit()
+	s.quit()
+	return &emptypb.Empty{}, nil
 }
 
-func (s *Service) quit() error {
+func (s *Service) quit() {
 	// Windows is notably slow at Quitting. We do it in a goroutine to speed things up a bit.
 	go func() {
-		var err error
+		if s.parentPID >= 0 {
+			s.parentPIDDoneCh <- struct{}{}
+		}
+
 		if s.isStreamingEvents() {
-			if err = s.stopEventStream(); err != nil {
+			if err := s.stopEventStream(); err != nil {
 				s.log.WithError(err).Error("Quit failed.")
 			}
 		}
@@ -111,8 +115,6 @@ func (s *Service) quit() error {
 		// The following call is launched as a goroutine, as it will wait for current calls to end, including this one.
 		s.grpcServer.GracefulStop()
 	}()
-
-	return nil
 }
 
 // Restart implement the Restart gRPC service call.

internal/frontend/grpc/service_stream.go

@@ -71,8 +71,9 @@ func (s *Service) RunEventStream(request *EventStreamRequest, server Bridge_RunE
 				return err
 			}
 		case <-server.Context().Done():
-			s.log.Debug("Client closed the stream, exiting")
-			return s.quit()
+			s.log.Info("Client closed the stream, initiating shutdown")
+			s.quit()
+			return nil
 		}
 	}
 }