Merge pull request #106388 from alexzielenski/ssa-ignore-nonsemantic-changes

Ignore non-semantic changes to objects

staging/src/k8s.io/apimachinery/pkg/conversion/deep_equal.go

@@ -34,3 +34,14 @@ func EqualitiesOrDie(funcs ...interface{}) Equalities {
 	}
 	return e
 }
+
+// Performs a shallow copy of the equalities map
+func (e Equalities) Copy() Equalities {
+	result := Equalities{reflect.Equalities{}}
+
+	for key, value := range e.Equalities {
+		result.Equalities[key] = value
+	}
+
+	return result
+}

staging/src/k8s.io/apimachinery/third_party/forked/golang/reflect/deep_equal.go

@@ -100,7 +100,8 @@ func makeUsefulPanic(v reflect.Value) {
 // Tests for deep equality using reflected types. The map argument tracks
 // comparisons that have already been seen, which allows short circuiting on
 // recursive types.
-func (e Equalities) deepValueEqual(v1, v2 reflect.Value, visited map[visit]bool, depth int) bool {
+// equateNilAndEmpty controls whether empty maps/slices are equivalent to nil
+func (e Equalities) deepValueEqual(v1, v2 reflect.Value, visited map[visit]bool, equateNilAndEmpty bool, depth int) bool {
 	defer makeUsefulPanic(v1)
 
 	if !v1.IsValid() || !v2.IsValid() {
@@ -150,17 +151,36 @@ func (e Equalities) deepValueEqual(v1, v2 reflect.Value, visited map[visit]bool,
 		// We don't need to check length here because length is part of
 		// an array's type, which has already been filtered for.
 		for i := 0; i < v1.Len(); i++ {
-			if !e.deepValueEqual(v1.Index(i), v2.Index(i), visited, depth+1) {
+			if !e.deepValueEqual(v1.Index(i), v2.Index(i), visited, equateNilAndEmpty, depth+1) {
 				return false
 			}
 		}
 		return true
 	case reflect.Slice:
-		if (v1.IsNil() || v1.Len() == 0) != (v2.IsNil() || v2.Len() == 0) {
-			return false
-		}
-		if v1.IsNil() || v1.Len() == 0 {
-			return true
+		if equateNilAndEmpty {
+			if (v1.IsNil() || v1.Len() == 0) != (v2.IsNil() || v2.Len() == 0) {
+				return false
+			}
+
+			if v1.IsNil() || v1.Len() == 0 {
+				return true
+			}
+		} else {
+			if v1.IsNil() != v2.IsNil() {
+				return false
+			}
+
+			// Optimize nil and empty cases
+			// Two lists that are BOTH nil are equal
+			// No need to check v2 is nil since v1.IsNil == v2.IsNil from above
+			if v1.IsNil() {
+				return true
+			}
+
+			// Two lists that are both empty and both non nil are equal
+			if v1.Len() == 0 || v2.Len() == 0 {
+				return true
+			}
 		}
 		if v1.Len() != v2.Len() {
 			return false
@@ -169,7 +189,7 @@ func (e Equalities) deepValueEqual(v1, v2 reflect.Value, visited map[visit]bool,
 			return true
 		}
 		for i := 0; i < v1.Len(); i++ {
-			if !e.deepValueEqual(v1.Index(i), v2.Index(i), visited, depth+1) {
+			if !e.deepValueEqual(v1.Index(i), v2.Index(i), visited, equateNilAndEmpty, depth+1) {
 				return false
 			}
 		}
@@ -178,22 +198,40 @@ func (e Equalities) deepValueEqual(v1, v2 reflect.Value, visited map[visit]bool,
 		if v1.IsNil() || v2.IsNil() {
 			return v1.IsNil() == v2.IsNil()
 		}
-		return e.deepValueEqual(v1.Elem(), v2.Elem(), visited, depth+1)
-	case reflect.Pointer:
-		return e.deepValueEqual(v1.Elem(), v2.Elem(), visited, depth+1)
+		return e.deepValueEqual(v1.Elem(), v2.Elem(), visited, equateNilAndEmpty, depth+1)
+	case reflect.Ptr:
+		return e.deepValueEqual(v1.Elem(), v2.Elem(), visited, equateNilAndEmpty, depth+1)
 	case reflect.Struct:
 		for i, n := 0, v1.NumField(); i < n; i++ {
-			if !e.deepValueEqual(v1.Field(i), v2.Field(i), visited, depth+1) {
+			if !e.deepValueEqual(v1.Field(i), v2.Field(i), visited, equateNilAndEmpty, depth+1) {
 				return false
 			}
 		}
 		return true
 	case reflect.Map:
-		if (v1.IsNil() || v1.Len() == 0) != (v2.IsNil() || v2.Len() == 0) {
-			return false
-		}
-		if v1.IsNil() || v1.Len() == 0 {
-			return true
+		if equateNilAndEmpty {
+			if (v1.IsNil() || v1.Len() == 0) != (v2.IsNil() || v2.Len() == 0) {
+				return false
+			}
+			if v1.IsNil() || v1.Len() == 0 {
+				return true
+			}
+		} else {
+			if v1.IsNil() != v2.IsNil() {
+				return false
+			}
+
+			// Optimize nil and empty cases
+			// Two maps that are BOTH nil are equal
+			// No need to check v2 is nil since v1.IsNil == v2.IsNil from above
+			if v1.IsNil() {
+				return true
+			}
+
+			// Two maps that are both empty and both non nil are equal
+			if v1.Len() == 0 || v2.Len() == 0 {
+				return true
+			}
 		}
 		if v1.Len() != v2.Len() {
 			return false
@@ -202,7 +240,7 @@ func (e Equalities) deepValueEqual(v1, v2 reflect.Value, visited map[visit]bool,
 			return true
 		}
 		for _, k := range v1.MapKeys() {
-			if !e.deepValueEqual(v1.MapIndex(k), v2.MapIndex(k), visited, depth+1) {
+			if !e.deepValueEqual(v1.MapIndex(k), v2.MapIndex(k), visited, equateNilAndEmpty, depth+1) {
 				return false
 			}
 		}
@@ -232,6 +270,14 @@ func (e Equalities) deepValueEqual(v1, v2 reflect.Value, visited map[visit]bool,
 // Unexported field members cannot be compared and will cause an informative panic; you must add an Equality
 // function for these types.
 func (e Equalities) DeepEqual(a1, a2 interface{}) bool {
+	return e.deepEqual(a1, a2, true)
+}
+
+func (e Equalities) DeepEqualWithNilDifferentFromEmpty(a1, a2 interface{}) bool {
+	return e.deepEqual(a1, a2, false)
+}
+
+func (e Equalities) deepEqual(a1, a2 interface{}, equateNilAndEmpty bool) bool {
 	if a1 == nil || a2 == nil {
 		return a1 == a2
 	}
@@ -240,7 +286,7 @@ func (e Equalities) DeepEqual(a1, a2 interface{}) bool {
 	if v1.Type() != v2.Type() {
 		return false
 	}
-	return e.deepValueEqual(v1, v2, make(map[visit]bool), 0)
+	return e.deepValueEqual(v1, v2, make(map[visit]bool), equateNilAndEmpty, 0)
 }
 
 func (e Equalities) deepValueDerive(v1, v2 reflect.Value, visited map[visit]bool, depth int) bool {

staging/src/k8s.io/apimachinery/third_party/forked/golang/reflect/deep_equal_test.go

@@ -16,6 +16,10 @@ func TestEqualities(t *testing.T) {
 	type Baz struct {
 		Y Bar
 	}
+	type Zap struct {
+		A []int
+		B map[string][]int
+	}
 	err := e.AddFuncs(
 		func(a, b int) bool {
 			return a+1 == b
@@ -32,10 +36,12 @@ func TestEqualities(t *testing.T) {
 		X int
 	}
 
-	table := []struct {
+	type Case struct {
 		a, b  interface{}
 		equal bool
-	}{
+	}
+
+	table := []Case{
 		{1, 2, true},
 		{2, 1, false},
 		{"foo", "fo", false},
@@ -70,6 +76,26 @@ func TestEqualities(t *testing.T) {
 			t.Errorf("Expected (%+v == %+v) == %v, but got %v", item.a, item.b, e, a)
 		}
 	}
+
+	// Cases which hinge upon implicit nil/empty map/slice equality
+	implicitTable := []Case{
+		{map[string][]int{}, map[string][]int(nil), true},
+		{[]int{}, []int(nil), true},
+		{map[string][]int{"foo": nil}, map[string][]int{"foo": {}}, true},
+		{Zap{A: nil, B: map[string][]int{"foo": nil}}, Zap{A: []int{}, B: map[string][]int{"foo": {}}}, true},
+	}
+
+	for _, item := range implicitTable {
+		if e, a := item.equal, e.DeepEqual(item.a, item.b); e != a {
+			t.Errorf("Expected (%+v == %+v) == %v, but got %v", item.a, item.b, e, a)
+		}
+	}
+
+	for _, item := range implicitTable {
+		if e, a := !item.equal, e.DeepEqualWithNilDifferentFromEmpty(item.a, item.b); e != a {
+			t.Errorf("Expected (%+v == %+v) == %v, but got %v", item.a, item.b, e, a)
+		}
+	}
 }
 
 func TestDerivatives(t *testing.T) {

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

@@ -0,0 +1,180 @@
+/*
+Copyright 2021 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package fieldmanager
+
+import (
+	"context"
+	"fmt"
+	"os"
+	"reflect"
+	"strconv"
+	"time"
+
+	"k8s.io/apimachinery/pkg/api/equality"
+	"k8s.io/apimachinery/pkg/api/meta"
+	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+	"k8s.io/apimachinery/pkg/conversion"
+	"k8s.io/apimachinery/pkg/runtime"
+	"k8s.io/apiserver/pkg/endpoints/metrics"
+	"k8s.io/klog/v2"
+)
+
+func determineAvoidNoopTimestampUpdatesEnabled() bool {
+	if avoidNoopTimestampUpdatesString, exists := os.LookupEnv("KUBE_APISERVER_AVOID_NOOP_SSA_TIMESTAMP_UPDATES"); exists {
+		if ret, err := strconv.ParseBool(avoidNoopTimestampUpdatesString); err == nil {
+			return ret
+		} else {
+			klog.Errorf("failed to parse envar KUBE_APISERVER_AVOID_NOOP_SSA_TIMESTAMP_UPDATES: %v", err)
+		}
+	}
+
+	// enabled by default
+	return true
+}
+
+var (
+	avoidNoopTimestampUpdatesEnabled = determineAvoidNoopTimestampUpdatesEnabled()
+)
+
+var avoidTimestampEqualities = func() conversion.Equalities {
+	var eqs = equality.Semantic.Copy()
+
+	err := eqs.AddFunc(
+		func(a, b metav1.ManagedFieldsEntry) bool {
+			// Two objects' managed fields are equivalent if, ignoring timestamp,
+			//	the objects are deeply equal.
+			a.Time = nil
+			b.Time = nil
+			return reflect.DeepEqual(a, b)
+		},
+	)
+
+	if err != nil {
+		panic(err)
+	}
+
+	return eqs
+}()
+
+// IgnoreManagedFieldsTimestampsTransformer reverts timestamp updates
+// if the non-managed parts of the object are equivalent
+func IgnoreManagedFieldsTimestampsTransformer(
+	_ context.Context,
+	newObj runtime.Object,
+	oldObj runtime.Object,
+) (res runtime.Object, err error) {
+	if !avoidNoopTimestampUpdatesEnabled {
+		return newObj, nil
+	}
+
+	outcome := "unequal_objects_fast"
+	start := time.Now()
+	err = nil
+	res = nil
+
+	defer func() {
+		if err != nil {
+			outcome = "error"
+		}
+
+		metrics.RecordTimestampComparisonLatency(outcome, time.Since(start))
+	}()
+
+	// If managedFields modulo timestamps are unchanged
+	//		and
+	//	rest of object is unchanged
+	//		then
+	//	revert any changes to timestamps in managed fields
+	//		(to prevent spurious ResourceVersion bump)
+	//
+	// Procecure:
+	// Do a quicker check to see if just managed fields modulo timestamps are
+	//	unchanged. If so, then do the full, slower check.
+	//
+	// In most cases which actually update the object, the managed fields modulo
+	//	timestamp check will fail, and we will be able to return early.
+	//
+	// In other cases, the managed fields may be exactly the same,
+	// 	except for timestamp, but the objects are the different. This is the
+	//	slow path which checks the full object.
+	oldAccessor, err := meta.Accessor(oldObj)
+	if err != nil {
+		return nil, fmt.Errorf("failed to acquire accessor for oldObj: %v", err)
+	}
+
+	accessor, err := meta.Accessor(newObj)
+	if err != nil {
+		return nil, fmt.Errorf("failed to acquire accessor for newObj: %v", err)
+	}
+
+	oldManagedFields := oldAccessor.GetManagedFields()
+	newManagedFields := accessor.GetManagedFields()
+
+	if len(oldManagedFields) != len(newManagedFields) {
+		// Return early if any managed fields entry was added/removed.
+		// We want to retain user expectation that even if they write to a field
+		// whose value did not change, they will still result as the field
+		// manager at the end.
+		return newObj, nil
+	} else if len(newManagedFields) == 0 {
+		// This transformation only makes sense when managedFields are
+		// non-empty
+		return newObj, nil
+	}
+
+	// This transformation only makes sense if the managed fields has at least one
+	// changed timestamp; and are otherwise equal. Return early if there are no
+	// changed timestamps.
+	allTimesUnchanged := true
+	for i, e := range newManagedFields {
+		if !e.Time.Equal(oldManagedFields[i].Time) {
+			allTimesUnchanged = false
+			break
+		}
+	}
+
+	if allTimesUnchanged {
+		return newObj, nil
+	}
+
+	// This condition ensures the managed fields are always compared first. If
+	//	this check fails, the if statement will short circuit. If the check
+	// 	succeeds the slow path is taken which compares entire objects.
+	if !avoidTimestampEqualities.DeepEqualWithNilDifferentFromEmpty(oldManagedFields, newManagedFields) {
+		return newObj, nil
+	}
+
+	if avoidTimestampEqualities.DeepEqualWithNilDifferentFromEmpty(newObj, oldObj) {
+		// Remove any changed timestamps, so that timestamp is not the only
+		// change seen by etcd.
+		//
+		// newManagedFields is known to be exactly pairwise equal to
+		// oldManagedFields except for timestamps.
+		//
+		// Simply replace possibly changed new timestamps with their old values.
+		for idx := 0; idx < len(oldManagedFields); idx++ {
+			newManagedFields[idx].Time = oldManagedFields[idx].Time
+		}
+
+		accessor.SetManagedFields(newManagedFields)
+		outcome = "equal_objects"
+		return newObj, nil
+	}
+
+	outcome = "unequal_objects_slow"
+	return newObj, nil
+}

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

@@ -659,8 +659,13 @@ func (p *patcher) patchResource(ctx context.Context, scope *RequestScope) (runti
 		return obj, nil
 	}
 
+	transformers := []rest.TransformFunc{p.applyPatch, p.applyAdmission, dedupOwnerReferencesTransformer}
+	if scope.FieldManager != nil {
+		transformers = append(transformers, fieldmanager.IgnoreManagedFieldsTimestampsTransformer)
+	}
+
 	wasCreated := false
-	p.updatedObjectInfo = rest.DefaultUpdatedObjectInfo(nil, p.applyPatch, p.applyAdmission, dedupOwnerReferencesTransformer)
+	p.updatedObjectInfo = rest.DefaultUpdatedObjectInfo(nil, transformers...)
 	requestFunc := func() (runtime.Object, error) {
 		// Pass in UpdateOptions to override UpdateStrategy.AllowUpdateOnCreate
 		options := patchToUpdateOptions(p.options)

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

@@ -191,6 +191,15 @@ func UpdateResource(r rest.Updater, scope *RequestScope, admit admission.Interfa
 			})
 		}
 
+		// Ignore changes that only affect managed fields
+		// timestamps. FieldManager can't know about changes
+		// like normalized fields, defaulted fields and other
+		// mutations.
+		// Only makes sense when SSA field manager is being used
+		if scope.FieldManager != nil {
+			transformers = append(transformers, fieldmanager.IgnoreManagedFieldsTimestampsTransformer)
+		}
+
 		createAuthorizerAttributes := authorizer.AttributesRecord{
 			User:            userInfo,
 			ResourceRequest: true,

staging/src/k8s.io/apiserver/pkg/endpoints/metrics/metrics.go

@@ -238,6 +238,18 @@ var (
 		[]string{"source", "status"},
 	)
 
+	requestTimestampComparisonDuration = compbasemetrics.NewHistogramVec(
+		&compbasemetrics.HistogramOpts{
+			Name:           "apiserver_request_timestamp_comparison_time",
+			Help:           "Time taken for comparison of old vs new objects in UPDATE or PATCH requests",
+			Buckets:        []float64{0.0001, 0.0003, 0.001, 0.003, 0.01, 0.03, 0.1, 0.3, 1.0, 5.0},
+			StabilityLevel: compbasemetrics.ALPHA,
+		},
+		// Path the code takes to reach a conclusion:
+		// i.e. unequalObjectsFast, unequalObjectsSlow, equalObjectsSlow
+		[]string{"code_path"},
+	)
+
 	metrics = []resettableCollector{
 		deprecatedRequestGauge,
 		requestCounter,
@@ -256,6 +268,7 @@ var (
 		requestFilterDuration,
 		requestAbortsTotal,
 		requestPostTimeoutTotal,
+		requestTimestampComparisonDuration,
 	}
 
 	// these are the valid request methods which we report in our metrics. Any other request methods
@@ -366,6 +379,10 @@ func RecordFilterLatency(ctx context.Context, name string, elapsed time.Duration
 	requestFilterDuration.WithContext(ctx).WithLabelValues(name).Observe(elapsed.Seconds())
 }
 
+func RecordTimestampComparisonLatency(codePath string, elapsed time.Duration) {
+	requestTimestampComparisonDuration.WithLabelValues(codePath).Observe(elapsed.Seconds())
+}
+
 func RecordRequestPostTimeout(source string, status string) {
 	requestPostTimeoutTotal.WithLabelValues(source, status).Inc()
 }

test/integration/apiserver/apply/apply_test.go

@@ -248,6 +248,185 @@ func TestNoOpUpdateSameResourceVersion(t *testing.T) {
 	}
 }
 
+func getRV(obj runtime.Object) (string, error) {
+	acc, err := meta.Accessor(obj)
+	if err != nil {
+		return "", err
+	}
+	return acc.GetResourceVersion(), nil
+}
+
+// TestNoSemanticUpdateAppleSameResourceVersion makes sure that APPLY requests which makes no semantic changes
+// will not change the resource version (no write to etcd is done)
+//
+// Some of the non-semantic changes are:
+// - Applying an atomic struct that removes a default
+// - Changing Quantity or other fields that are normalized
+func TestNoSemanticUpdateApplySameResourceVersion(t *testing.T) {
+	defer featuregatetesting.SetFeatureGateDuringTest(t, utilfeature.DefaultFeatureGate, genericfeatures.ServerSideApply, true)()
+
+	client, closeFn := setup(t)
+	defer closeFn()
+
+	ssBytes := []byte(`{
+		"apiVersion": "apps/v1",
+		"kind": "StatefulSet",
+		"metadata": {
+			"name": "nginx",
+			"labels": {"app": "nginx"}
+		},
+		"spec": {
+			"serviceName": "nginx",
+			"selector": { "matchLabels": {"app": "nginx"}},
+			"template": {
+				"metadata": {
+					"labels": {"app": "nginx"}
+				},
+				"spec": {
+					"containers": [{
+						"name":  "nginx",
+						"image": "nginx",
+						"resources": {
+							"limits": {"memory": "2048Mi"}
+						}
+					}]
+				}
+			},
+			"volumeClaimTemplates": [{
+				"metadata": {"name": "nginx"},
+				"spec": {
+					"accessModes": ["ReadWriteOnce"],
+					"resources": {"requests": {"storage": "1Gi"}}
+				}
+			}]
+		}
+	}`)
+
+	obj, err := client.AppsV1().RESTClient().Patch(types.ApplyPatchType).
+		Namespace("default").
+		Param("fieldManager", "apply_test").
+		Resource("statefulsets").
+		Name("nginx").
+		Body(ssBytes).
+		Do(context.TODO()).
+		Get()
+	if err != nil {
+		t.Fatalf("Failed to create object: %v", err)
+	}
+
+	rvCreated, err := getRV(obj)
+	if err != nil {
+		t.Fatalf("Failed to get RV: %v", err)
+	}
+
+	// Sleep for one second to make sure that the times of each update operation is different.
+	time.Sleep(1200 * time.Millisecond)
+
+	obj, err = client.AppsV1().RESTClient().Patch(types.ApplyPatchType).
+		Namespace("default").
+		Param("fieldManager", "apply_test").
+		Resource("statefulsets").
+		Name("nginx").
+		Body(ssBytes).
+		Do(context.TODO()).
+		Get()
+	if err != nil {
+		t.Fatalf("Failed to create object: %v", err)
+	}
+	rvApplied, err := getRV(obj)
+	if err != nil {
+		t.Fatalf("Failed to get RV: %v", err)
+	}
+	if rvApplied != rvCreated {
+		t.Fatal("ResourceVersion changed after apply")
+	}
+}
+
+// TestNoSemanticUpdateAppleSameResourceVersion makes sure that PUT requests which makes no semantic changes
+// will not change the resource version (no write to etcd is done)
+//
+// Some of the non-semantic changes are:
+// - Applying an atomic struct that removes a default
+// - Changing Quantity or other fields that are normalized
+func TestNoSemanticUpdatePutSameResourceVersion(t *testing.T) {
+	defer featuregatetesting.SetFeatureGateDuringTest(t, utilfeature.DefaultFeatureGate, genericfeatures.ServerSideApply, true)()
+
+	client, closeFn := setup(t)
+	defer closeFn()
+
+	ssBytes := []byte(`{
+		"apiVersion": "apps/v1",
+		"kind": "StatefulSet",
+		"metadata": {
+			"name": "nginx",
+			"labels": {"app": "nginx"}
+		},
+		"spec": {
+			"serviceName": "nginx",
+			"selector": { "matchLabels": {"app": "nginx"}},
+			"template": {
+				"metadata": {
+					"labels": {"app": "nginx"}
+				},
+				"spec": {
+					"containers": [{
+						"name":  "nginx",
+						"image": "nginx",
+						"resources": {
+							"limits": {"memory": "2048Mi"}
+						}
+					}]
+				}
+			},
+			"volumeClaimTemplates": [{
+				"metadata": {"name": "nginx"},
+				"spec": {
+					"accessModes": ["ReadWriteOnce"],
+					"resources": { "requests": { "storage": "1Gi"}}
+				}
+			}]
+		}
+	}`)
+
+	obj, err := client.AppsV1().RESTClient().Post().
+		Namespace("default").
+		Param("fieldManager", "apply_test").
+		Resource("statefulsets").
+		Body(ssBytes).
+		Do(context.TODO()).
+		Get()
+	if err != nil {
+		t.Fatalf("Failed to create object: %v", err)
+	}
+
+	rvCreated, err := getRV(obj)
+	if err != nil {
+		t.Fatalf("Failed to get RV: %v", err)
+	}
+
+	// Sleep for one second to make sure that the times of each update operation is different.
+	time.Sleep(1200 * time.Millisecond)
+
+	obj, err = client.AppsV1().RESTClient().Put().
+		Namespace("default").
+		Param("fieldManager", "apply_test").
+		Resource("statefulsets").
+		Name("nginx").
+		Body(ssBytes).
+		Do(context.TODO()).
+		Get()
+	if err != nil {
+		t.Fatalf("Failed to create object: %v", err)
+	}
+	rvApplied, err := getRV(obj)
+	if err != nil {
+		t.Fatalf("Failed to get RV: %v", err)
+	}
+	if rvApplied != rvCreated {
+		t.Fatal("ResourceVersion changed after similar PUT")
+	}
+}
+
 // TestCreateOnApplyFailsWithUID makes sure that PATCH requests with the apply content type
 // will not create the object if it doesn't already exist and it specifies a UID
 func TestCreateOnApplyFailsWithUID(t *testing.T) {

test/integration/apiserver/timestamp_transformer_test.go

@@ -0,0 +1,149 @@
+/*
+Copyright 2020 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package apiserver
+
+import (
+	"context"
+	"encoding/json"
+	"math/rand"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+	v1 "k8s.io/api/core/v1"
+	k8sfuzz "k8s.io/apimachinery/pkg/api/apitesting/fuzzer"
+	"k8s.io/apimachinery/pkg/api/meta"
+	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+	"k8s.io/apimachinery/pkg/runtime"
+	"k8s.io/apimachinery/pkg/runtime/serializer"
+	"k8s.io/apiserver/pkg/endpoints/handlers/fieldmanager"
+	k8stest "k8s.io/kubernetes/pkg/api/testing"
+)
+
+func convertToUnstructured(b *testing.B, obj runtime.Object) runtime.Object {
+	converter := fieldmanager.DeducedTypeConverter{}
+	typed, err := converter.ObjectToTyped(obj)
+	require.NoError(b, err)
+	res, err := converter.TypedToObject(typed)
+	require.NoError(b, err)
+	return res
+}
+
+func doBench(b *testing.B, useUnstructured bool, shortCircuit bool) {
+	var (
+		expectedLarge runtime.Object
+		actualLarge   runtime.Object
+		expectedSmall runtime.Object
+		actualSmall   runtime.Object
+	)
+
+	scheme := runtime.NewScheme()
+	codecs := serializer.NewCodecFactory(scheme)
+	seed := rand.Int63()
+	fuzzer := k8sfuzz.FuzzerFor(k8stest.FuzzerFuncs, rand.NewSource(seed), codecs)
+	fuzzer.NilChance(0)
+
+	fuzzer.MaxDepth(1000).NilChance(0.2).NumElements(2, 15)
+	pod := &v1.Pod{}
+	fuzzer.Fuzz(pod)
+
+	fuzzer.NilChance(0.2).NumElements(10, 100).MaxDepth(10)
+	deployment := &v1.Endpoints{}
+	fuzzer.Fuzz(deployment)
+
+	bts, err := json.Marshal(deployment)
+	require.NoError(b, err)
+	b.Logf("Small (Deployment): %v bytes", len(bts))
+	bts, err = json.Marshal(pod)
+	require.NoError(b, err)
+	b.Logf("Large (Pod): %v bytes", len(bts))
+
+	expectedLarge = deployment
+	expectedSmall = pod
+
+	if useUnstructured {
+		expectedSmall = convertToUnstructured(b, expectedSmall)
+		expectedLarge = convertToUnstructured(b, expectedLarge)
+	}
+
+	actualLarge = expectedLarge.DeepCopyObject()
+	actualSmall = expectedSmall.DeepCopyObject()
+
+	if shortCircuit {
+		// Modify managed fields of the compared objects to induce a short circuit
+		now := metav1.Now()
+		extraEntry := &metav1.ManagedFieldsEntry{
+			Manager:    "sidecar_controller",
+			Operation:  metav1.ManagedFieldsOperationApply,
+			APIVersion: "apps/v1",
+			Time:       &now,
+			FieldsType: "FieldsV1",
+			FieldsV1: &metav1.FieldsV1{
+				Raw: []byte(`{"f:metadata":{"f:labels":{"f:sidecar_version":{}}},"f:spec":{"f:template":{"f:spec":{"f:containers":{"k:{\"name\":\"sidecar\"}":{".":{},"f:image":{},"f:name":{}}}}}}}`),
+			},
+		}
+
+		largeMeta, err := meta.Accessor(actualLarge)
+		require.NoError(b, err)
+		largeMeta.SetManagedFields(append(largeMeta.GetManagedFields(), *extraEntry))
+
+		smallMeta, err := meta.Accessor(actualSmall)
+		require.NoError(b, err)
+		smallMeta.SetManagedFields(append(smallMeta.GetManagedFields(), *extraEntry))
+	}
+
+	b.ResetTimer()
+
+	b.Run("Large", func(b2 *testing.B) {
+		for i := 0; i < b2.N; i++ {
+			if _, err := fieldmanager.IgnoreManagedFieldsTimestampsTransformer(
+				context.TODO(),
+				actualLarge,
+				expectedLarge,
+			); err != nil {
+				b2.Fatal(err)
+			}
+		}
+	})
+
+	b.Run("Small", func(b2 *testing.B) {
+		for i := 0; i < b2.N; i++ {
+			if _, err := fieldmanager.IgnoreManagedFieldsTimestampsTransformer(
+				context.TODO(),
+				actualSmall,
+				expectedSmall,
+			); err != nil {
+				b2.Fatal(err)
+			}
+		}
+	})
+}
+
+func BenchmarkIgnoreManagedFieldsTimestampTransformerStructuredShortCircuit(b *testing.B) {
+	doBench(b, false, true)
+}
+
+func BenchmarkIgnoreManagedFieldsTimestampTransformerStructuredWorstCase(b *testing.B) {
+	doBench(b, false, false)
+}
+
+func BenchmarkIgnoreManagedFieldsTimestampTransformerUnstructuredShortCircuit(b *testing.B) {
+	doBench(b, true, true)
+}
+
+func BenchmarkIgnoreManagedFieldsTimestampTransformerUnstructuredWorstCase(b *testing.B) {
+	doBench(b, true, false)
+}