Reduce System.Mutate runtime by 87% (#1454)

* Benchmark System.Mutate

Signed-off-by: Will Beason <willbeason@google.com>

* Early exit Mutate if no mutations

Signed-off-by: Will Beason <willbeason@google.com>

Co-authored-by: Oren Shomron <shomron@gmail.com>

pkg/mutation/system.go

@@ -105,14 +105,21 @@ func (s *System) Mutate(obj *unstructured.Unstructured, ns *corev1.Namespace) (b
 
 			if m.Matches(obj, ns) {
 				mutated, err := m.Mutate(obj)
-				if mutated && (*MutationLoggingEnabled || *MutationAnnotationsEnabled) {
+				if mutated {
 					appliedMutations = append(appliedMutations, m)
 				}
 				if err != nil {
 					return false, errors.Wrapf(err, "mutation %s for mutator %v failed for %s %s %s %s", mutationUUID, m.ID(), obj.GroupVersionKind().Group, obj.GroupVersionKind().Kind, obj.GetNamespace(), obj.GetName())
 				}
 			}
 		}
+
+		if len(appliedMutations) == 0 {
+			// If no mutations were applied, we can safely assume the object is
+			// identical to before.
+			return i > 0, nil
+		}
+
 		if cmp.Equal(old, obj) {
 			if i == 0 {
 				return false, nil

pkg/mutation/system_benchmark_test.go

@@ -0,0 +1,62 @@
+package mutation
+
+import (
+	"encoding/json"
+	"testing"
+
+	"github.com/open-policy-agent/gatekeeper/apis/mutations/v1alpha1"
+	"github.com/open-policy-agent/gatekeeper/pkg/mutation/match"
+	"github.com/open-policy-agent/gatekeeper/pkg/mutation/mutators"
+	"k8s.io/apimachinery/pkg/apis/meta/v1/unstructured"
+	"k8s.io/apimachinery/pkg/runtime"
+)
+
+func makeValue(v interface{}) runtime.RawExtension {
+	v2 := map[string]interface{}{
+		"value": v,
+	}
+	j, err := json.Marshal(v2)
+	if err != nil {
+		panic(err)
+	}
+	return runtime.RawExtension{Raw: j}
+}
+
+func assign(value interface{}, location string) *v1alpha1.Assign {
+	result := &v1alpha1.Assign{
+		Spec: v1alpha1.AssignSpec{
+			ApplyTo: []match.ApplyTo{{
+				Groups:   []string{"*"},
+				Versions: []string{"*"},
+				Kinds:    []string{"*"},
+			}},
+			Location: location,
+			Parameters: v1alpha1.Parameters{
+				Assign: makeValue(value),
+			},
+		},
+	}
+
+	return result
+}
+
+func BenchmarkSystem_Mutate(b *testing.B) {
+	s := NewSystem()
+
+	a := assign("", "spec")
+	m, err := mutators.MutatorForAssign(a)
+	if err != nil {
+		b.Fatal(err)
+	}
+
+	err = s.Upsert(m)
+	if err != nil {
+		b.Fatal(err)
+	}
+
+	for i := 0; i < b.N; i++ {
+		u := &unstructured.Unstructured{}
+
+		_, _ = s.Mutate(u, nil)
+	}
+}

pkg/mutation/system_test.go

@@ -98,7 +98,7 @@ func (m *fakeMutator) SchemaBindings() []schema.GroupVersionKind {
 	return m.GVKs
 }
 
-var mutators = []types.Mutator{
+var initMutators = []types.Mutator{
 	&fakeMutator{MID: types.ID{Group: "bbb", Kind: "aaa", Namespace: "aaa", Name: "aaa"}},
 	&fakeMutator{MID: types.ID{Group: "aaa", Kind: "bbb", Namespace: "ccc", Name: "ddd"}},
 	&fakeMutator{MID: types.ID{Group: "aaa", Kind: "bbb", Namespace: "aaa", Name: "aaa"}},
@@ -116,7 +116,7 @@ func TestSorting(t *testing.T) {
 	}{
 		{
 			tname:   "testsort",
-			initial: mutators,
+			initial: initMutators,
 			expected: []types.Mutator{
 				&fakeMutator{MID: types.ID{Group: "aaa", Kind: "aaa", Namespace: "aaa", Name: "aaa"}},
 				&fakeMutator{MID: types.ID{Group: "aaa", Kind: "aaa", Namespace: "ccc", Name: "ddd"}},
@@ -129,7 +129,7 @@ func TestSorting(t *testing.T) {
 		},
 		{
 			tname:   "testremove",
-			initial: mutators,
+			initial: initMutators,
 			expected: []types.Mutator{
 				&fakeMutator{MID: types.ID{Group: "aaa", Kind: "aaa", Namespace: "aaa", Name: "aaa"}},
 				&fakeMutator{MID: types.ID{Group: "aaa", Kind: "aaa", Namespace: "ccc", Name: "ddd"}},
@@ -143,7 +143,7 @@ func TestSorting(t *testing.T) {
 		},
 		{
 			tname:   "testaddingsame",
-			initial: mutators,
+			initial: initMutators,
 			expected: []types.Mutator{
 				&fakeMutator{MID: types.ID{Group: "aaa", Kind: "aaa", Namespace: "aaa", Name: "aaa"}},
 				&fakeMutator{MID: types.ID{Group: "aaa", Kind: "aaa", Namespace: "ccc", Name: "ddd"}},
@@ -158,7 +158,7 @@ func TestSorting(t *testing.T) {
 		},
 		{
 			tname:   "testaddingdifferent",
-			initial: mutators,
+			initial: initMutators,
 			expected: []types.Mutator{
 				&fakeMutator{MID: types.ID{Group: "aaa", Kind: "aaa", Namespace: "aaa", Name: "aaa"}},
 				&fakeMutator{MID: types.ID{Group: "aaa", Kind: "aaa", Namespace: "ccc", Name: "ddd"}},