Persist final downlink metadata

pkg/dwn/downlink.go

@@ -292,7 +292,9 @@ func (s *DownlinkSession) eventLoop() {
 	// Make sure to clean up the tmp file once we finish
 	defer os.Remove(stagingFileName)
 	defer func() {
-		s.msg.TimeEnd = timestamppb.New(time.Now().UTC())
+		if s.msg.TimeEnd == nil {
+			s.msg.TimeEnd = timestamppb.New(time.Now().UTC())
+		}
 		s.span.AddEvent(
 			"finished",
 			trace.WithAttributes(
@@ -498,16 +500,7 @@ func (s *DownlinkSession) eventLoop() {
 
 	s.msg.Size = offset
 
-	s.span.AddEvent("writing metadata file")
-	mdData, err := proto.Marshal(s.msg)
-	if err != nil {
-		s.logger.Error("failed to encode downlink metadata", "path", metadataFilePath, "err", err)
-	} else {
-		_, err = metadataFile.Write(mdData)
-		if err != nil {
-			s.logger.Error("failed to write downlink metadata", "path", metadataFilePath, "err", err)
-		}
-	}
+	s.writeMetadataFile(metadataFile, metadataFilePath)
 
 	s.span.AddEvent("syncing filesystem")
 	outFile.Sync()
@@ -538,6 +531,31 @@ func (s *DownlinkSession) eventLoop() {
 			}
 		}
 	}
+
+	s.msg.TimeEnd = timestamppb.New(time.Now().UTC())
+	s.writeMetadataFile(metadataFile, metadataFilePath)
+	metadataFile.Sync()
+}
+
+func (s *DownlinkSession) writeMetadataFile(metadataFile *os.File, metadataFilePath string) {
+	s.span.AddEvent("writing metadata file")
+	mdData, err := proto.Marshal(s.msg)
+	if err != nil {
+		s.logger.Error("failed to encode downlink metadata", "path", metadataFilePath, "err", err)
+		return
+	}
+
+	if _, err = metadataFile.Seek(0, 0); err != nil {
+		s.logger.Error("failed to seek downlink metadata", "path", metadataFilePath, "err", err)
+		return
+	}
+	if err = metadataFile.Truncate(0); err != nil {
+		s.logger.Error("failed to truncate downlink metadata", "path", metadataFilePath, "err", err)
+		return
+	}
+	if _, err = metadataFile.Write(mdData); err != nil {
+		s.logger.Error("failed to write downlink metadata", "path", metadataFilePath, "err", err)
+	}
 }
 
 // Wait for file downlink to be processed

pkg/dwn/downlink_test.go

@@ -15,6 +15,7 @@ import (
 	"github.com/nasa/hermes/pkg/log"
 	"github.com/nasa/hermes/pkg/pb"
 	"github.com/stretchr/testify/assert"
+	"google.golang.org/protobuf/proto"
 )
 
 func AssertFileContents(t *testing.T, path string, expectedContents []byte) {
@@ -45,6 +46,20 @@ func AssertFileContents(t *testing.T, path string, expectedContents []byte) {
 	assert.EqualValues(t, expectedContents, contents, "file contents don't match expected", path)
 }
 
+func ReadDownlinkMetadata(t *testing.T, path string) *pb.FileDownlink {
+	t.Helper()
+	data, err := os.ReadFile(path + ".md.pb")
+	if !assert.NoError(t, err) {
+		return nil
+	}
+
+	metadata := &pb.FileDownlink{}
+	if !assert.NoError(t, proto.Unmarshal(data, metadata)) {
+		return nil
+	}
+	return metadata
+}
+
 func ClearFromSlice(s []byte, i, j int) {
 	for ; i < j; i++ {
 		s[i] = 0
@@ -114,6 +129,13 @@ func TestCompleteSuccess(t *testing.T) {
 	assert.Equal(t, "/root/test.dat", dl.SourcePath)
 	assert.Equal(t, pb.FileDownlinkCompletionStatus_DOWNLINK_COMPLETED, dl.Status)
 	AssertFileContents(t, dl.FilePath, fullFile)
+
+	metadata := ReadDownlinkMetadata(t, dl.FilePath)
+	if metadata != nil {
+		assert.Equal(t, dl.Status, metadata.Status)
+		assert.NotNil(t, metadata.TimeEnd)
+		assert.True(t, metadata.TimeEnd.AsTime().Equal(dl.TimeEnd.AsTime()))
+	}
 }
 
 func TestMissingChunkMiddle(t *testing.T) {