Preserve Annotation to Prevent GC

pkg/apis/serving/metadata_validation.go

@@ -39,6 +39,7 @@ var (
 		RevisionLastPinnedAnnotationKey,
 		RoutingStateModifiedAnnotationKey,
 		GroupNamePrefix+"forceUpgrade",
+		RevisionPreservedAnnotationKey,
 	)
 )
 

pkg/apis/serving/metadata_validation_test.go

@@ -133,6 +133,14 @@ func TestValidateObjectMetadata(t *testing.T) {
 				RevisionLastPinnedAnnotationKey: "pinned-val",
 			},
 		},
+	}, {
+		name: "valid preserve annotation label",
+		objectMeta: &metav1.ObjectMeta{
+			GenerateName: "some-name",
+			Annotations: map[string]string{
+				RevisionLastPinnedAnnotationKey: "true",
+			},
+		},
 	}, {
 		name: "invalid knative prefix annotation",
 		objectMeta: &metav1.ObjectMeta{

pkg/apis/serving/register.go

@@ -33,6 +33,10 @@ const (
 	// pinned a revision
 	RevisionLastPinnedAnnotationKey = GroupName + "/lastPinned"
 
+	// RevisionPreservedAnnotationKey is the annotation key used for preventing garbage collector
+	// from automatically deleting the revision.
+	RevisionPreservedAnnotationKey = GroupName + "/no-gc"
+
 	// RouteLabelKey is the label key attached to a Configuration indicating by
 	// which Route it is configured as traffic target.
 	// The key is also attached to Revision resources to indicate they are directly

pkg/reconciler/gc/v2/gc.go

@@ -19,6 +19,7 @@ package v2
 import (
 	"context"
 	"sort"
+	"strings"
 	"time"
 
 	"go.uber.org/zap"
@@ -61,6 +62,9 @@ func Collect(
 	})
 
 	for _, rev := range revs[gcSkipOffset:] {
+		if strings.EqualFold(rev.ObjectMeta.Annotations[serving.RevisionPreservedAnnotationKey], "true") {
+			continue
+		}
 		if isRevisionStale(ctx, rev, config) {
 			err := client.ServingV1().Revisions(rev.Namespace).Delete(rev.Name, &metav1.DeleteOptions{})
 			if err != nil {

pkg/reconciler/gc/v2/gc_test.go

@@ -208,6 +208,43 @@ func TestCollect(t *testing.T) {
 				WithCreationTimestamp(oldest),
 				WithLastPinned(old)),
 		},
+	}, {
+		name: "keep oldest because of the preserve annotation",
+		cfg: cfg("keep-oldest", "foo", 5556,
+			WithLatestCreated("5556"),
+			WithLatestReady("5556"),
+			WithConfigObservedGen),
+		revs: []*v1.Revision{
+			rev("keep-oldest", "foo", 5554, MarkRevisionReady,
+				WithRevName("5554"),
+				WithCreationTimestamp(oldest),
+				WithLastPinned(oldest),
+				WithRevisionPreserveAnnotation()),
+			rev("keep-oldest", "foo", 5555, MarkRevisionReady,
+				WithRevName("5555"),
+				WithCreationTimestamp(older),
+				WithLastPinned(older)),
+			rev("keep-oldest", "foo", 5556, MarkRevisionReady,
+				WithRevName("5556"),
+				WithCreationTimestamp(old),
+				WithLastPinned(old)),
+			rev("keep-oldest", "foo", 5557, MarkRevisionReady,
+				WithRevName("5557"),
+				WithCreationTimestamp(tenMinutesAgo),
+				WithLastPinned(tenMinutesAgo)),
+		},
+		wantDeletes: []clientgotesting.DeleteActionImpl{{
+			ActionImpl: clientgotesting.ActionImpl{
+				Namespace: "foo",
+				Verb:      "delete",
+				Resource: schema.GroupVersionResource{
+					Group:    "serving.knative.dev",
+					Version:  "v1",
+					Resource: "revisions",
+				},
+			},
+			Name: "5555",
+		}},
 	}}
 
 	cfgMap := &config.Config{

pkg/testing/v1/revision.go

@@ -92,6 +92,16 @@ func WithLastPinned(t time.Time) RevisionOption {
 	}
 }
 
+// WithRevisionPreserveAnnotation updates the annotation with preserve key.
+func WithRevisionPreserveAnnotation() RevisionOption {
+	return func(rev *v1.Revision) {
+		rev.Annotations = kmeta.UnionMaps(rev.Annotations,
+			map[string]string{
+				serving.RevisionPreservedAnnotationKey: "true",
+			})
+	}
+}
+
 // WithRoutingStateModified updates the annotation to the provided timestamp.
 func WithRoutingStateModified(t time.Time) RevisionOption {
 	return func(rev *v1.Revision) {