Reduce a deployments selector to only match the revision uid (#2818)

Prior the selector criteria would include all the revision's labels.
This would cause reconciliation of a revision's deployment to fail
when a revision label was added/removed.

pkg/reconciler/v1alpha1/revision/cruds.go

@@ -63,6 +63,10 @@ func (c *Reconciler) checkAndUpdateDeployment(ctx context.Context, rev *v1alpha1
 	// Preserve the current scale of the Deployment.
 	deployment.Spec.Replicas = have.Spec.Replicas
 
+	// Preserve the label selector since it's immutable
+	// TODO(dprotaso) Determine other immutable properties
+	deployment.Spec.Selector = have.Spec.Selector
+
 	// If the spec we want is the spec we have, then we're good.
 	if equality.Semantic.DeepEqual(have.Spec, deployment.Spec) {
 		return have, Unchanged, nil

pkg/reconciler/v1alpha1/revision/resources/deploy_test.go

@@ -1160,9 +1160,7 @@ func TestMakeDeployment(t *testing.T) {
 				Replicas: &one,
 				Selector: &metav1.LabelSelector{
 					MatchLabels: map[string]string{
-						serving.RevisionLabelKey: "bar",
-						serving.RevisionUID:      "1234",
-						AppLabelKey:              "bar",
+						serving.RevisionUID: "1234",
 					},
 				},
 				ProgressDeadlineSeconds: &ProgressDeadlineSeconds,
@@ -1232,9 +1230,7 @@ func TestMakeDeployment(t *testing.T) {
 				Replicas: &one,
 				Selector: &metav1.LabelSelector{
 					MatchLabels: map[string]string{
-						serving.RevisionLabelKey: "bar",
-						serving.RevisionUID:      "1234",
-						AppLabelKey:              "bar",
+						serving.RevisionUID: "1234",
 					},
 				},
 				ProgressDeadlineSeconds: &ProgressDeadlineSeconds,
@@ -1299,9 +1295,7 @@ func TestMakeDeployment(t *testing.T) {
 				Replicas: &one,
 				Selector: &metav1.LabelSelector{
 					MatchLabels: map[string]string{
-						serving.RevisionLabelKey: "bar",
-						serving.RevisionUID:      "1234",
-						AppLabelKey:              "bar",
+						serving.RevisionUID: "1234",
 					},
 				},
 				ProgressDeadlineSeconds: &ProgressDeadlineSeconds,
@@ -1372,9 +1366,7 @@ func TestMakeDeployment(t *testing.T) {
 				Replicas: &one,
 				Selector: &metav1.LabelSelector{
 					MatchLabels: map[string]string{
-						serving.RevisionLabelKey: "bar",
-						serving.RevisionUID:      "1234",
-						AppLabelKey:              "bar",
+						serving.RevisionUID: "1234",
 					},
 				},
 				ProgressDeadlineSeconds: &ProgressDeadlineSeconds,

pkg/reconciler/v1alpha1/revision/resources/meta.go

@@ -44,7 +44,11 @@ func makeLabels(revision *v1alpha1.Revision) map[string]string {
 
 // makeSelector constructs the Selector we will apply to K8s resources.
 func makeSelector(revision *v1alpha1.Revision) *metav1.LabelSelector {
-	return &metav1.LabelSelector{MatchLabels: makeLabels(revision)}
+	return &metav1.LabelSelector{
+		MatchLabels: map[string]string{
+			serving.RevisionUID: string(revision.UID),
+		},
+	}
 }
 
 // makeAnnotations creates the annotations we will apply to

pkg/reconciler/v1alpha1/revision/resources/meta_test.go

@@ -90,7 +90,10 @@ func TestMakeLabels(t *testing.T) {
 			if diff := cmp.Diff(test.want, got); diff != "" {
 				t.Errorf("makeLabels (-want, +got) = %v", diff)
 			}
-			wantSelector := &metav1.LabelSelector{MatchLabels: test.want}
+
+			wantSelector := &metav1.LabelSelector{
+				MatchLabels: map[string]string{serving.RevisionUID: "1234"},
+			}
 			gotSelector := makeSelector(test.rev)
 			if diff := cmp.Diff(wantSelector, gotSelector); diff != "" {
 				t.Errorf("makeLabels (-want, +got) = %v", diff)