create probabilistic SkipNonAppliedManager

Author: jennybuckley

staging/src/k8s.io/apiserver/pkg/endpoints/handlers/fieldmanager/fieldmanager.go

@@ -33,6 +33,10 @@ import (
 // TODO(jennybuckley): Determine if this is really the best value. Ideally we wouldn't unnecessarily merge too many entries.
 const DefaultMaxUpdateManagers int = 10
 
+// DefaultTrackOnCreateProbability defines the default probability that the field management of an object
+// starts being tracked from the object's creation, instead of from the first time the object is applied to.
+const DefaultTrackOnCreateProbability float32 = 0.11494204485329620070
+
 // Managed groups a fieldpath.ManagedFields together with the timestamps associated with each operation.
 type Managed interface {
 	// Fields gets the fieldpath.ManagedFields.
@@ -92,7 +96,7 @@ func newDefaultFieldManager(f Manager, objectCreater runtime.ObjectCreater, kind
 	f = NewStripMetaManager(f)
 	f = NewBuildManagerInfoManager(f, kind.GroupVersion())
 	f = NewCapManagersManager(f, DefaultMaxUpdateManagers)
-	f = NewSkipNonAppliedManager(f, objectCreater, kind)
+	f = NewProbabilisticSkipNonAppliedManager(f, objectCreater, kind, DefaultTrackOnCreateProbability)
 	return NewFieldManager(f)
 }
 

staging/src/k8s.io/apiserver/pkg/endpoints/handlers/fieldmanager/skipnonapplied.go

@@ -18,7 +18,9 @@ package fieldmanager
 
 import (
 	"fmt"
+	"math/rand"
 
+	"k8s.io/apimachinery/pkg/api/meta"
 	"k8s.io/apimachinery/pkg/runtime"
 	"k8s.io/apimachinery/pkg/runtime/schema"
 )
@@ -28,25 +30,48 @@ type skipNonAppliedManager struct {
 	objectCreater          runtime.ObjectCreater
 	gvk                    schema.GroupVersionKind
 	beforeApplyManagerName string
+	probability            float32
 }
 
 var _ Manager = &skipNonAppliedManager{}
 
 // NewSkipNonAppliedManager creates a new wrapped FieldManager that only starts tracking managers after the first apply.
 func NewSkipNonAppliedManager(fieldManager Manager, objectCreater runtime.ObjectCreater, gvk schema.GroupVersionKind) Manager {
+	return NewProbabilisticSkipNonAppliedManager(fieldManager, objectCreater, gvk, 0.0)
+}
+
+// NewProbabilisticSkipNonAppliedManager creates a new wrapped FieldManager that starts tracking managers after the first apply,
+// or starts tracking on create with p probability.
+func NewProbabilisticSkipNonAppliedManager(fieldManager Manager, objectCreater runtime.ObjectCreater, gvk schema.GroupVersionKind, p float32) Manager {
 	return &skipNonAppliedManager{
 		fieldManager:           fieldManager,
 		objectCreater:          objectCreater,
 		gvk:                    gvk,
 		beforeApplyManagerName: "before-first-apply",
+		probability:            p,
 	}
 }
 
 // Update implements Manager.
 func (f *skipNonAppliedManager) Update(liveObj, newObj runtime.Object, managed Managed, manager string) (runtime.Object, Managed, error) {
-	if len(managed.Fields()) == 0 {
+	accessor, err := meta.Accessor(liveObj)
+	if err != nil {
 		return newObj, managed, nil
 	}
+
+	// If managed fields is empty, we need to determine whether to skip tracking managed fields.
+	if len(managed.Fields()) == 0 {
+		// Check if the operation is a create, by checking whether lastObj's UID is empty.
+		// If the operation is create, P(tracking managed fields) = f.probability
+		// If the operation is update, skip tracking managed fields, since we already know managed fields is empty.
+		if len(accessor.GetUID()) == 0 {
+			if f.probability <= rand.Float32() {
+				return newObj, managed, nil
+			}
+		} else {
+			return newObj, managed, nil
+		}
+	}
 	return f.fieldManager.Update(liveObj, newObj, managed, manager)
 }