Report a measured zero incremental instead of erasing it (#10309)

* Report a measured zero incremental instead of erasing it

A CBT incremental with an exactly zero delta -- nothing changed since
the parent -- was reported identically to a backup that moved the whole
device. `velero backup describe --details` printed only
"Moved data Size (bytes): 3221225472" with no incremental line, and
status.incrementalBytes was absent, for a run that transferred nothing.
The best possible CBT outcome displayed as the worst, and was
indistinguishable from a genuine full, a whole-device fallback, or a
backup predating incremental accounting.

The zero was being erased twice. Besides the API status fields,
datapath.BackupResult also carried omitempty, and that struct crosses a
JSON boundary from the data mover pod to the controller (see
micro_service_watcher.go), so the value was destroyed before the
controller could persist it. Every uploader always reports a figure
there, so 0 internally always means "transferred nothing" -- dropping
omitempty is sufficient and correct for that hop.

The API fields move to *int64 rather than just dropping omitempty. The
field shipped in v1.18.0-v1.18.2, so backups exist whose stored volume
info has no incrementalSize at all; with a plain int64 those unmarshal
to 0 and would render "Incremental data Size (bytes): 0", a false claim
of a perfect incremental on a run that never measured one. nil means not
measured, a pointer to 0 means measured zero. Both fields already carry
+optional, so the generated CRD schema is unchanged and no regeneration
is required.

Display gates relax from > 0 to != nil in all three places, including
volumesByPod.Add, whose signature takes *int64 now; the restore describer
passes nil, which is correct since restores measure no incremental.

Verified live: the same zero-delta scenario that reported <none> now
reports 0 and renders "Incremental data Size (bytes): 0", while an older
backup described with the new client still correctly prints no
incremental line at all.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Signed-off-by: Tiger Kaovilai <tkaovila@redhat.com>
(cherry picked from commit 6c7aa9d588f6d5eab134d4ce19c92b838f45557c)
Signed-off-by: Tiger Kaovilai <tkaovila@redhat.com>

* gofmt: fix import ordering in backup_test.go

Signed-off-by: Tiger Kaovilai <tkaovila@redhat.com>

* Regenerate CRDs for IncrementalBytes pointer type

make update-crd was missed in the original commit. Regenerated with
the pinned controller-gen v0.16.5 to avoid unrelated version-annotation
churn across other CRDs.

Signed-off-by: Tiger Kaovilai <tkaovila@redhat.com>

* Add changelog for #10309

Signed-off-by: Tiger Kaovilai <tkaovila@redhat.com>

* Address review: make IncrementalBytes a pointer to preserve backward compat

Per Lyndon-Li's review on #10309: dropping omitempty on the plain int64
field breaks compatibility with a data mover from release-1.17 or
earlier that predates IncrementalBytes and never writes the key -- the
new controller would unmarshal a zero value ("nothing transferred")
instead of recognizing the field is simply absent ("not measured").

Switch to *int64 with omitempty restored:
- an old mover's omitted key unmarshals to nil ("not measured")
- a current mover's genuine zero still serializes the key, unmarshaling
  to a non-nil pointer to 0 ("measured zero")
- nonzero values work exactly as before
- an old controller can still unmarshal a numeric value from a new mover

pkg/controller/data_upload_controller.go and pod_volume_backup_controller.go
assign the wire-struct field directly to their already-*int64,omitempty
CRD status field instead of re-wrapping it with ptr.To, since both are
now the same pointer type.

Signed-off-by: Tiger Kaovilai <tkaovila@redhat.com>

* Fix CI: update marshal-fail test assertions for IncrementalBytes pointer

Both backup_micro_service_test.go files hardcoded the %v-formatted
zero-value BackupResult struct in an error-message assertion. Now that
IncrementalBytes is *int64, its zero value prints as <nil> instead of 0.

Signed-off-by: Tiger Kaovilai <tkaovila@redhat.com>

---------

Signed-off-by: Tiger Kaovilai <tkaovila@redhat.com>
Co-authored-by: Claude Fable 5 <noreply@anthropic.com>

changelogs/unreleased/10309-kaovilai

@@ -0,0 +1 @@
+Report a measured zero-byte incremental instead of erasing it from status

config/crd/v1/bases/velero.io_podvolumebackups.yaml

@@ -205,8 +205,12 @@ spec:
                 nullable: true
                 type: string
               incrementalBytes:
-                description: IncrementalBytes holds the number of bytes new or changed
-                  since the last backup
+                description: |-
+                  IncrementalBytes holds the number of bytes new or changed since the last backup.
+                  A nil value means the uploader did not report a figure; a pointer to 0 means it
+                  reported zero, i.e. nothing changed and nothing was transferred. The two are
+                  distinct: erasing a measured zero makes a perfect incremental indistinguishable
+                  from a full transfer in every downstream report.
                 format: int64
                 type: integer
               message:

config/crd/v2alpha1/bases/velero.io_datauploads.yaml

@@ -192,8 +192,12 @@ spec:
                 nullable: true
                 type: object
               incrementalBytes:
-                description: IncrementalBytes holds the number of bytes new or changed
-                  since the last backup
+                description: |-
+                  IncrementalBytes holds the number of bytes new or changed since the last backup.
+                  A nil value means the uploader did not report a figure; a pointer to 0 means it
+                  reported zero, i.e. nothing changed and nothing was transferred. The two are
+                  distinct: erasing a measured zero makes a perfect incremental indistinguishable
+                  from a full transfer in every downstream report.
                 format: int64
                 type: integer
               message:

internal/volume/volumes_information.go

@@ -175,8 +175,11 @@ type SnapshotDataMovementInfo struct {
 	// Moved snapshot data size.
 	Size int64 `json:"size"`
 
-	// Moved snapshot incremental size.
-	IncrementalSize int64 `json:"incrementalSize,omitempty"`
+	// Moved snapshot incremental size, i.e. the bytes actually transferred. Nil means
+	// the uploader reported no figure (including backups taken before this was
+	// recorded); a pointer to 0 means it transferred nothing, which is the ideal
+	// incremental and must stay distinguishable from "unknown".
+	IncrementalSize *int64 `json:"incrementalSize,omitempty"`
 
 	// The DataUpload's Status.Phase value
 	Phase velerov2alpha1.DataUploadPhase
@@ -225,8 +228,9 @@ type PodVolumeInfo struct {
 	// The snapshot corresponding volume size.
 	Size int64 `json:"size,omitempty"`
 
-	// The incremental snapshot size.
-	IncrementalSize int64 `json:"incrementalSize,omitempty"`
+	// The incremental snapshot size, i.e. the bytes actually transferred. Nil means
+	// the uploader reported no figure; a pointer to 0 means it transferred nothing.
+	IncrementalSize *int64 `json:"incrementalSize,omitempty"`
 
 	// The type of the uploader that uploads the data. The valid values are `kopia` and `restic`.
 	UploaderType string `json:"uploaderType"`

pkg/apis/velero/v1/pod_volume_backup_types.go

@@ -124,9 +124,13 @@ type PodVolumeBackupStatus struct {
 	// +optional
 	Progress shared.DataMoveOperationProgress `json:"progress,omitempty"`
 
-	// IncrementalBytes holds the number of bytes new or changed since the last backup
+	// IncrementalBytes holds the number of bytes new or changed since the last backup.
+	// A nil value means the uploader did not report a figure; a pointer to 0 means it
+	// reported zero, i.e. nothing changed and nothing was transferred. The two are
+	// distinct: erasing a measured zero makes a perfect incremental indistinguishable
+	// from a full transfer in every downstream report.
 	// +optional
-	IncrementalBytes int64 `json:"incrementalBytes,omitempty"`
+	IncrementalBytes *int64 `json:"incrementalBytes,omitempty"`
 
 	// AcceptedTimestamp records the time the pod volume backup is to be prepared.
 	// The server's time is used for AcceptedTimestamp

pkg/apis/velero/v1/zz_generated.deepcopy.go

@@ -1055,6 +1055,11 @@ func (in *PodVolumeBackupStatus) DeepCopyInto(out *PodVolumeBackupStatus) {
 		*out = (*in).DeepCopy()
 	}
 	out.Progress = in.Progress
+	if in.IncrementalBytes != nil {
+		in, out := &in.IncrementalBytes, &out.IncrementalBytes
+		*out = new(int64)
+		**out = **in
+	}
 	if in.AcceptedTimestamp != nil {
 		in, out := &in.AcceptedTimestamp, &out.AcceptedTimestamp
 		*out = (*in).DeepCopy()

pkg/apis/velero/v2alpha1/data_upload_types.go

@@ -165,9 +165,13 @@ type DataUploadStatus struct {
 	// +optional
 	Progress shared.DataMoveOperationProgress `json:"progress,omitempty"`
 
-	// IncrementalBytes holds the number of bytes new or changed since the last backup
+	// IncrementalBytes holds the number of bytes new or changed since the last backup.
+	// A nil value means the uploader did not report a figure; a pointer to 0 means it
+	// reported zero, i.e. nothing changed and nothing was transferred. The two are
+	// distinct: erasing a measured zero makes a perfect incremental indistinguishable
+	// from a full transfer in every downstream report.
 	// +optional
-	IncrementalBytes int64 `json:"incrementalBytes,omitempty"`
+	IncrementalBytes *int64 `json:"incrementalBytes,omitempty"`
 
 	// Node is name of the node where the DataUpload is processed.
 	// +optional

pkg/apis/velero/v2alpha1/zz_generated.deepcopy.go

@@ -270,6 +270,11 @@ func (in *DataUploadStatus) DeepCopyInto(out *DataUploadStatus) {
 		*out = (*in).DeepCopy()
 	}
 	out.Progress = in.Progress
+	if in.IncrementalBytes != nil {
+		in, out := &in.IncrementalBytes, &out.IncrementalBytes
+		*out = new(int64)
+		**out = **in
+	}
 	if in.AcceptedTimestamp != nil {
 		in, out := &in.AcceptedTimestamp, &out.AcceptedTimestamp
 		*out = (*in).DeepCopy()

pkg/backup/backup_test.go

@@ -43,6 +43,7 @@ import (
 	"k8s.io/apimachinery/pkg/labels"
 	"k8s.io/apimachinery/pkg/runtime"
 	"k8s.io/apimachinery/pkg/runtime/schema"
+	"k8s.io/utils/ptr"
 
 	"github.com/vmware-tanzu/velero/internal/resourcepolicies"
 	"github.com/vmware-tanzu/velero/internal/volume"
@@ -5681,7 +5682,7 @@ func TestUpdateVolumeInfos(t *testing.T) {
 						RetainedSnapshot: "vs-1",
 						SnapshotHandle:   "snapshot-id",
 						Size:             1000,
-						IncrementalSize:  500,
+						IncrementalSize:  ptr.To(int64(500)),
 						Phase:            velerov2alpha1.DataUploadPhaseFailed,
 					},
 				},
@@ -5721,7 +5722,7 @@ func TestUpdateVolumeInfos(t *testing.T) {
 						RetainedSnapshot: "vs-1",
 						SnapshotHandle:   "snapshot-id",
 						Size:             1000,
-						IncrementalSize:  500,
+						IncrementalSize:  ptr.To(int64(500)),
 						Phase:            velerov2alpha1.DataUploadPhaseCompleted,
 					},
 				},

pkg/builder/data_upload_builder.go

@@ -147,7 +147,7 @@ func (d *DataUploadBuilder) Progress(progress shared.DataMoveOperationProgress)
 
 // IncrementalBytes sets the DataUpload's IncrementalBytes.
 func (d *DataUploadBuilder) IncrementalBytes(incrementalBytes int64) *DataUploadBuilder {
-	d.object.Status.IncrementalBytes = incrementalBytes
+	d.object.Status.IncrementalBytes = &incrementalBytes
 	return d
 }
 

pkg/cmd/util/output/backup_describer.go

@@ -739,8 +739,12 @@ func describeDataMovement(d *Describer, details bool, info *volume.BackupVolumeI
 		d.Printf("\t\t\t\tData Mover: %s\n", dataMover)
 		d.Printf("\t\t\t\tUploader Type: %s\n", info.SnapshotDataMovementInfo.UploaderType)
 		d.Printf("\t\t\t\tMoved data Size (bytes): %d\n", info.SnapshotDataMovementInfo.Size)
-		if info.SnapshotDataMovementInfo.IncrementalSize > 0 {
-			d.Printf("\t\t\t\tIncremental data Size (bytes): %d\n", info.SnapshotDataMovementInfo.IncrementalSize)
+		// Print whenever the uploader measured a figure, including zero. A zero-delta
+		// incremental transfers nothing, which is the whole point of CBT; hiding it
+		// leaves only the volume size on display and makes the best possible result
+		// indistinguishable from a full transfer.
+		if info.SnapshotDataMovementInfo.IncrementalSize != nil {
+			d.Printf("\t\t\t\tIncremental data Size (bytes): %d\n", *info.SnapshotDataMovementInfo.IncrementalSize)
 		}
 		d.Printf("\t\t\t\tResult: %s\n", info.Result)
 	} else {
@@ -915,7 +919,7 @@ type volumesByPod struct {
 // Add adds a pod volume with the specified pod namespace, name
 // and volume to the appropriate group.
 // Used for both backup and restore
-func (v *volumesByPod) Add(namespace, name, volume, phase string, progress veleroapishared.DataMoveOperationProgress, incrementalBytes int64) {
+func (v *volumesByPod) Add(namespace, name, volume, phase string, progress veleroapishared.DataMoveOperationProgress, incrementalBytes *int64) {
 	if v.volumesByPodMap == nil {
 		v.volumesByPodMap = make(map[string]*podVolumeGroup)
 	}
@@ -925,8 +929,12 @@ func (v *volumesByPod) Add(namespace, name, volume, phase string, progress veler
 	// append backup progress percentage if backup is in progress
 	if phase == "In Progress" && progress.TotalBytes != 0 {
 		volume = fmt.Sprintf("%s (%.2f%%)", volume, float64(progress.BytesDone)/float64(progress.TotalBytes)*100)
-	} else if phase == string(velerov1api.PodVolumeBackupPhaseCompleted) && incrementalBytes > 0 {
-		volume = fmt.Sprintf("%s (size: %v, incremental size: %v)", volume, progress.TotalBytes, incrementalBytes)
+	} else if phase == string(velerov1api.PodVolumeBackupPhaseCompleted) && incrementalBytes != nil {
+		// Report the incremental figure whenever it was measured, including zero. Zero is
+		// the best possible outcome - nothing changed, so nothing was transferred - and
+		// suppressing it leaves only the volume size on display, which reads as a full
+		// transfer.
+		volume = fmt.Sprintf("%s (size: %v, incremental size: %v)", volume, progress.TotalBytes, *incrementalBytes)
 	} else if (phase == string(velerov1api.PodVolumeBackupPhaseCompleted) ||
 		phase == string(velerov1api.PodVolumeRestorePhaseCompleted)) &&
 		progress.TotalBytes > 0 {

pkg/cmd/util/output/backup_describer_test.go

@@ -25,6 +25,7 @@ import (
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 	corev1api "k8s.io/api/core/v1"
+	"k8s.io/utils/ptr"
 
 	"github.com/vmware-tanzu/velero/internal/volume"
 	velerov1api "github.com/vmware-tanzu/velero/pkg/apis/velero/v1"
@@ -629,7 +630,7 @@ func TestCSISnapshots(t *testing.T) {
 						SnapshotHandle:  "fake-repo-id-5",
 						OperationID:     "fake-operation-5",
 						Size:            100,
-						IncrementalSize: 50,
+						IncrementalSize: ptr.To(int64(50)),
 						Phase:           velerov2alpha1.DataUploadPhaseFailed,
 					},
 				},

pkg/cmd/util/output/backup_structured_describer.go

@@ -467,9 +467,13 @@ func describeDataMovementInSF(details bool, info *volume.BackupVolumeInfo, snaps
 
 		dataMovement["uploaderType"] = info.SnapshotDataMovementInfo.UploaderType
 		dataMovement["result"] = string(info.Result)
-		if info.SnapshotDataMovementInfo.Size > 0 || info.SnapshotDataMovementInfo.IncrementalSize > 0 {
+		if info.SnapshotDataMovementInfo.Size > 0 {
 			dataMovement["size"] = info.SnapshotDataMovementInfo.Size
-			dataMovement["incrementalSize"] = info.SnapshotDataMovementInfo.IncrementalSize
+		}
+		// Emit whenever measured, including zero - a zero-delta incremental transferred
+		// nothing, and that has to be reportable rather than absent.
+		if info.SnapshotDataMovementInfo.IncrementalSize != nil {
+			dataMovement["incrementalSize"] = *info.SnapshotDataMovementInfo.IncrementalSize
 		}
 
 		snapshotDetail["dataMovement"] = dataMovement

pkg/cmd/util/output/restore_describer.go

@@ -417,7 +417,7 @@ func describePodVolumeRestores(d *Describer, restores []velerov1api.PodVolumeRes
 		restoresByPod := new(volumesByPod)
 
 		for _, restore := range restoresByPhase[phase] {
-			restoresByPod.Add(restore.Spec.Pod.Namespace, restore.Spec.Pod.Name, restore.Spec.Volume, phase, restore.Status.Progress, 0)
+			restoresByPod.Add(restore.Spec.Pod.Namespace, restore.Spec.Pod.Name, restore.Spec.Volume, phase, restore.Status.Progress, nil)
 		}
 
 		d.Printf("\t%s:\n", phase)

pkg/datamover/backup_micro_service_test.go

@@ -152,7 +152,7 @@ func TestOnDataUploadCompleted(t *testing.T) {
 		{
 			name:        "marshal fail",
 			marshalErr:  errors.New("fake-marshal-error"),
-			expectedErr: "Failed to marshal backup result { false { } 0 0}: fake-marshal-error",
+			expectedErr: "Failed to marshal backup result { false { } 0 <nil>}: fake-marshal-error",
 		},
 		{
 			name:                "succeed",

pkg/datapath/data_path.go

@@ -22,6 +22,7 @@ import (
 
 	"github.com/cockroachdb/errors"
 	"github.com/sirupsen/logrus"
+	"k8s.io/utils/ptr"
 	"sigs.k8s.io/controller-runtime/pkg/client"
 
 	"github.com/vmware-tanzu/velero/internal/credentials"
@@ -220,7 +221,7 @@ func (dp *generalDataPath) StartBackup(source AccessPoint, uploaderConfig map[st
 			}
 			dp.callbacks.OnFailed(context.Background(), dp.namespace, dp.jobName, dataPathErr)
 		} else {
-			dp.callbacks.OnCompleted(context.Background(), dp.namespace, dp.jobName, Result{Backup: BackupResult{snapshotID, emptySnapshot, source, totalBytes, incrementalBytes}})
+			dp.callbacks.OnCompleted(context.Background(), dp.namespace, dp.jobName, Result{Backup: BackupResult{snapshotID, emptySnapshot, source, totalBytes, ptr.To(incrementalBytes)}})
 		}
 	}()
 

pkg/datapath/data_path_test.go

@@ -24,6 +24,7 @@ import (
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/mock"
 	"github.com/stretchr/testify/require"
+	"k8s.io/utils/ptr"
 
 	velerotest "github.com/vmware-tanzu/velero/pkg/test"
 	"github.com/vmware-tanzu/velero/pkg/uploader/provider"
@@ -82,10 +83,11 @@ func TestAsyncBackup(t *testing.T) {
 			},
 			result: Result{
 				Backup: BackupResult{
-					SnapshotID:    "fake-snapshot",
-					EmptySnapshot: false,
-					Source:        AccessPoint{ByPath: "fake-path"},
-					TotalBytes:    1000,
+					SnapshotID:       "fake-snapshot",
+					EmptySnapshot:    false,
+					Source:           AccessPoint{ByPath: "fake-path"},
+					TotalBytes:       1000,
+					IncrementalBytes: ptr.To(int64(0)),
 				},
 			},
 			path: "fake-path",
@@ -96,7 +98,11 @@ func TestAsyncBackup(t *testing.T) {
 		t.Run(test.name, func(t *testing.T) {
 			dp := newGeneralDataPath("job-1", "test", nil, "velero", Callbacks{}, velerotest.NewLogger()).(*generalDataPath)
 			mockProvider := providerMock.NewProvider(t)
-			mockProvider.On("RunBackup", mock.Anything, mock.Anything, mock.Anything, mock.Anything, mock.Anything, mock.Anything, mock.Anything, mock.Anything, mock.Anything, mock.Anything).Return(test.result.Backup.SnapshotID, test.result.Backup.EmptySnapshot, test.result.Backup.TotalBytes, test.result.Backup.IncrementalBytes, test.err)
+			var incrementalBytes int64
+			if test.result.Backup.IncrementalBytes != nil {
+				incrementalBytes = *test.result.Backup.IncrementalBytes
+			}
+			mockProvider.On("RunBackup", mock.Anything, mock.Anything, mock.Anything, mock.Anything, mock.Anything, mock.Anything, mock.Anything, mock.Anything, mock.Anything, mock.Anything).Return(test.result.Backup.SnapshotID, test.result.Backup.EmptySnapshot, test.result.Backup.TotalBytes, incrementalBytes, test.err)
 			mockProvider.On("Close", mock.Anything).Return(nil)
 			dp.uploaderProv = mockProvider
 			dp.initialized = true

pkg/datapath/micro_service_watcher_test.go

@@ -34,6 +34,7 @@ import (
 	"k8s.io/client-go/kubernetes"
 	kubeclientfake "k8s.io/client-go/kubernetes/fake"
 	corev1client "k8s.io/client-go/kubernetes/typed/core/v1"
+	"k8s.io/utils/ptr"
 	"sigs.k8s.io/controller-runtime/pkg/client/fake"
 
 	"github.com/vmware-tanzu/velero/pkg/builder"
@@ -510,6 +511,42 @@ func TestGetResultFromMessage(t *testing.T) {
 				},
 			},
 		},
+		{
+			// An old data mover (release-1.17 and earlier) predates IncrementalBytes and
+			// never writes the key at all -- this pins that its absence unmarshals to nil
+			// ("not measured"), not a zero value.
+			name:     "old mover message omits incrementalBytes -> nil",
+			taskType: TaskTypeBackup,
+			message:  "{\"snapshotID\":\"fake-snapshot-id\",\"emptySnapshot\":false,\"source\":{\"byPath\":\"fake-path-1\",\"volumeMode\":\"Block\"}}",
+			expectResult: Result{
+				Backup: BackupResult{
+					SnapshotID: "fake-snapshot-id",
+					Source: AccessPoint{
+						ByPath:  "fake-path-1",
+						VolMode: uploader.PersistentVolumeBlock,
+					},
+					IncrementalBytes: nil,
+				},
+			},
+		},
+		{
+			// A current mover reports a genuine zero explicitly -- this pins that the key
+			// being present with value 0 unmarshals to a non-nil pointer to 0 ("measured
+			// zero"), distinguishing it from the omitted-key case above.
+			name:     "current mover reports measured zero incrementalBytes -> non-nil zero",
+			taskType: TaskTypeBackup,
+			message:  "{\"snapshotID\":\"fake-snapshot-id\",\"emptySnapshot\":false,\"source\":{\"byPath\":\"fake-path-1\",\"volumeMode\":\"Block\"},\"incrementalBytes\":0}",
+			expectResult: Result{
+				Backup: BackupResult{
+					SnapshotID: "fake-snapshot-id",
+					Source: AccessPoint{
+						ByPath:  "fake-path-1",
+						VolMode: uploader.PersistentVolumeBlock,
+					},
+					IncrementalBytes: ptr.To(int64(0)),
+				},
+			},
+		},
 		{
 			name:     "succeed to unmarshall restore result",
 			taskType: TaskTypeRestore,

pkg/datapath/types.go

@@ -30,11 +30,15 @@ type Result struct {
 
 // BackupResult represents the result of a backup
 type BackupResult struct {
-	SnapshotID       string      `json:"snapshotID"`
-	EmptySnapshot    bool        `json:"emptySnapshot"`
-	Source           AccessPoint `json:"source,omitempty"`
-	TotalBytes       int64       `json:"totalBytes,omitempty"`
-	IncrementalBytes int64       `json:"incrementalBytes,omitempty"`
+	SnapshotID    string      `json:"snapshotID"`
+	EmptySnapshot bool        `json:"emptySnapshot"`
+	Source        AccessPoint `json:"source,omitempty"`
+	TotalBytes    int64       `json:"totalBytes,omitempty"`
+	// IncrementalBytes is a pointer so an old data mover (release-1.17 and earlier,
+	// which predates this field) that omits it unmarshals to nil -- "not measured" --
+	// while a current mover reporting a genuine zero still serializes the key and
+	// unmarshals to a non-nil zero, distinguishing "measured zero" from "not measured".
+	IncrementalBytes *int64 `json:"incrementalBytes,omitempty"`
 }
 
 // RestoreResult represents the result of a restore

pkg/podvolume/backup_micro_service_test.go

@@ -156,7 +156,7 @@ func TestOnDataPathCompleted(t *testing.T) {
 		{
 			name:        "marshal fail",
 			marshalErr:  errors.New("fake-marshal-error"),
-			expectedErr: "Failed to marshal backup result { false { } 0 0}: fake-marshal-error",
+			expectedErr: "Failed to marshal backup result { false { } 0 <nil>}: fake-marshal-error",
 		},
 		{
 			name:                "succeed",