Add systemd unit journal entries to error message

Signed-off-by: Daniel Weiße <dw@edgeless.systems>

debugd/internal/debugd/deploy/service.go

@@ -61,6 +61,7 @@ type SystemdUnit struct {
 type ServiceManager struct {
 	log                      *slog.Logger
 	dbus                     dbusClient
+	journal                  journalReader
 	fs                       afero.Fs
 	systemdUnitFilewriteLock sync.Mutex
 }
@@ -71,6 +72,7 @@ func NewServiceManager(log *slog.Logger) *ServiceManager {
 	return &ServiceManager{
 		log:                      log,
 		dbus:                     &dbusWrapper{},
+		journal:                  &journalctlWrapper{},
 		fs:                       fs,
 		systemdUnitFilewriteLock: sync.Mutex{},
 	}
@@ -99,6 +101,11 @@ type dbusConn interface {
 	Close()
 }
 
+type journalReader interface {
+	// ReadJournal reads the journal for a specific unit.
+	readJournal(unit string) string
+}
+
 // SystemdAction will perform a systemd action on a service unit (start, stop, restart, reload).
 func (s *ServiceManager) SystemdAction(ctx context.Context, request ServiceManagerRequest) error {
 	log := s.log.With(slog.String("unit", request.Unit), slog.String("action", request.Action.String()))
@@ -139,7 +146,8 @@ func (s *ServiceManager) SystemdAction(ctx context.Context, request ServiceManag
 		return nil
 
 	default:
-		return fmt.Errorf("performing action %q on systemd unit %q failed: expected %q but received %q", request.Action.String(), request.Unit, "done", result)
+		serviceJournal := s.journal.readJournal(request.Unit)
+		return fmt.Errorf("performing action %q on systemd unit %q failed: expected %q but received %q. systemd unit journal entries: %s", request.Action.String(), request.Unit, "done", result, serviceJournal)
 	}
 }
 

debugd/internal/debugd/deploy/service_test.go

@@ -104,6 +104,7 @@ func TestSystemdAction(t *testing.T) {
 			manager := ServiceManager{
 				log:                      logger.NewTest(t),
 				dbus:                     &tc.dbus,
+				journal:                  &stubJournalReader{},
 				fs:                       fs,
 				systemdUnitFilewriteLock: sync.Mutex{},
 			}
@@ -183,6 +184,7 @@ func TestWriteSystemdUnitFile(t *testing.T) {
 			manager := ServiceManager{
 				log:                      logger.NewTest(t),
 				dbus:                     &tc.dbus,
+				journal:                  &stubJournalReader{},
 				fs:                       fs,
 				systemdUnitFilewriteLock: sync.Mutex{},
 			}
@@ -296,6 +298,7 @@ func TestOverrideServiceUnitExecStart(t *testing.T) {
 			manager := ServiceManager{
 				log:                      logger.NewTest(t),
 				dbus:                     &tc.dbus,
+				journal:                  &stubJournalReader{},
 				fs:                       fs,
 				systemdUnitFilewriteLock: sync.Mutex{},
 			}
@@ -367,3 +370,9 @@ func (c *fakeDbusConn) ReloadContext(_ context.Context) error {
 }
 
 func (c *fakeDbusConn) Close() {}
+
+type stubJournalReader struct{}
+
+func (s *stubJournalReader) readJournal(_ string) string {
+	return ""
+}

debugd/internal/debugd/deploy/wrappers.go

@@ -8,6 +8,7 @@ package deploy
 
 import (
 	"context"
+	"os/exec"
 
 	"github.com/coreos/go-systemd/v22/dbus"
 )
@@ -48,3 +49,82 @@ func (c *dbusConnWrapper) ReloadContext(ctx context.Context) error {
 func (c *dbusConnWrapper) Close() {
 	c.conn.Close()
 }
+
+type journalctlWrapper struct{}
+
+func (j *journalctlWrapper) readJournal(unit string) string {
+	out, _ := exec.CommandContext(context.Background(), "journalctl", "-u", unit, "--no-pager").CombinedOutput()
+	return string(out)
+}
+
+/*
+type sdJournalWrapper struct{}
+
+// readJournal reads the journal for a specific unit.
+func (s *sdJournalWrapper) readJournal(unit string) string {
+	journal, err := sdjournal.NewJournal()
+	if err != nil {
+		log.Printf("opening journal: %s", err)
+		return ""
+	}
+	defer journal.Close()
+
+	// Filter the journal for the specified unit
+	filters := []string{
+		fmt.Sprintf("_SYSTEMD_UNIT=%s", unit),
+		fmt.Sprintf("UNIT=%s", unit),
+		fmt.Sprintf("OBJECT_SYSTEMD_UNIT=%s", unit),
+		fmt.Sprintf("_SYSTEMD_SLICE=%s", unit),
+		fmt.Sprintf("_SYSTEMD_USER_UNIT=%s", unit),
+		fmt.Sprintf("USER_UNIT=%s", unit),
+		fmt.Sprintf("COREDUMP_USER_UNIT=%s", unit),
+		fmt.Sprintf("OBJECT_SYSTEMD_USER_UNIT=%s", unit),
+		fmt.Sprintf("_SYSTEMD_USER_SLICE=%s", unit),
+	}
+	for _, filter := range filters {
+		if err := journal.AddMatch(filter); err != nil {
+			log.Printf("applying filter %q: %s", filter, err)
+			return ""
+		}
+		if err := journal.AddDisjunction(); err != nil {
+			log.Printf("adding disjunction to journal filter: %s", err)
+			return ""
+		}
+	}
+
+	// Seek to the beginning of the journal
+	if err := journal.SeekHead(); err != nil {
+		log.Printf("seeking journal tail: %s", err)
+		return ""
+	}
+
+	// Iterate over the journal entries
+	var previousCursor string
+	journalLog := &strings.Builder{}
+	for {
+		if _, err := journal.Next(); err != nil {
+			log.Printf("getting next entry in journal: %s", err)
+			return ""
+		}
+
+		entry, err := journal.GetEntry()
+		if err != nil {
+			log.Printf("getting journal entry: %s", err)
+			return ""
+		}
+
+		// Abort if we reached the end of the journal, i.e. the cursor didn't change
+		if entry.Cursor == previousCursor {
+			break
+		}
+		previousCursor = entry.Cursor
+
+		if _, err := journalLog.WriteString(entry.Fields[sdjournal.SD_JOURNAL_FIELD_MESSAGE] + "\n"); err != nil {
+			log.Printf("copying journal entry to buffer: %s", err)
+			return ""
+		}
+	}
+
+	return strings.TrimSpace(journalLog.String())
+}
+*/