add completion index as pod label

pkg/controller/job/indexed_job_utils.go

@@ -311,6 +311,14 @@ func addCompletionIndexAnnotation(template *v1.PodTemplateSpec, index int) {
 	template.Annotations[batch.JobCompletionIndexAnnotation] = strconv.Itoa(index)
 }
 
+func addCompletionIndexLabel(template *v1.PodTemplateSpec, index int) {
+	if template.Labels == nil {
+		template.Labels = make(map[string]string, 1)
+	}
+	// Use completion index annotation as label as well for consistency.
+	template.Labels[batch.JobCompletionIndexAnnotation] = strconv.Itoa(index)
+}
+
 func podGenerateNameWithIndex(jobName string, index int) string {
 	appendIndex := "-" + strconv.Itoa(index) + "-"
 	generateNamePrefix := jobName + appendIndex

pkg/controller/job/job_controller.go

@@ -1482,6 +1482,7 @@ func (jm *Controller) manageJob(ctx context.Context, job *batch.Job, activePods
 					if completionIndex != unknownCompletionIndex {
 						template = podTemplate.DeepCopy()
 						addCompletionIndexAnnotation(template, completionIndex)
+						addCompletionIndexLabel(template, completionIndex)
 						template.Spec.Hostname = fmt.Sprintf("%s-%d", job.Name, completionIndex)
 						generateName = podGenerateNameWithIndex(job.Name, completionIndex)
 					}

pkg/controller/job/job_controller_test.go

@@ -962,6 +962,7 @@ func checkIndexedJobPods(t *testing.T, control *controller.FakePodControl, wantI
 	gotIndexes := sets.New[int]()
 	for _, p := range control.Templates {
 		checkJobCompletionEnvVariable(t, &p.Spec)
+		checkJobCompletionLabel(t, &p)
 		ix := getCompletionIndex(p.Annotations)
 		if ix == -1 {
 			t.Errorf("Created pod %s didn't have completion index", p.Name)
@@ -4394,6 +4395,13 @@ func TestFinalizersRemovedExpectations(t *testing.T) {
 		t.Errorf("Timeout waiting for expectations (-want, +got):\n%s", diff)
 	}
 }
+func checkJobCompletionLabel(t *testing.T, p *v1.PodTemplateSpec) {
+	t.Helper()
+	labels := p.GetLabels()
+	if labels == nil || labels[batch.JobCompletionIndexAnnotation] == "" {
+		t.Errorf("missing expected pod label %s", batch.JobCompletionIndexAnnotation)
+	}
+}
 
 func checkJobCompletionEnvVariable(t *testing.T, spec *v1.PodSpec) {
 	t.Helper()