feat: add TransformStripCRDSchema for reduced cache memory usage

pkg/reconciler/customresourcesgate/cache.go

@@ -0,0 +1,58 @@
+/*
+Copyright 2025 The Crossplane 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 customresourcesgate
+
+import (
+	apiextensionsv1 "k8s.io/apiextensions-apiserver/pkg/apis/apiextensions/v1"
+)
+
+// TransformStripCRDSchema is a cache.TransformFunc that removes heavy fields
+// from CustomResourceDefinition objects before they are stored in the informer
+// cache. It strips:
+//   - Spec.Versions[].Schema (OpenAPI v3 validation schemas)
+//   - ObjectMeta.ManagedFields
+//   - The "kubectl.kubernetes.io/last-applied-configuration" annotation
+//
+// This significantly reduces memory usage in clusters with many CRDs. The CRD
+// gate reconciler only needs basic metadata (group, kind, version names, served
+// status) and status conditions to function correctly.
+//
+// Usage:
+//
+//	cache.Options{
+//	    ByObject: map[client.Object]cache.ByObject{
+//	        &apiextensionsv1.CustomResourceDefinition{}: {
+//	            Transform: customresourcesgate.TransformStripCRDSchema,
+//	        },
+//	    },
+//	}
+func TransformStripCRDSchema(obj any) (any, error) {
+	crd, ok := obj.(*apiextensionsv1.CustomResourceDefinition)
+	if !ok {
+		return obj, nil
+	}
+
+	for i := range crd.Spec.Versions {
+		crd.Spec.Versions[i].Schema = nil
+	}
+
+	crd.ManagedFields = nil
+
+	delete(crd.Annotations, "kubectl.kubernetes.io/last-applied-configuration")
+
+	return crd, nil
+}

pkg/reconciler/customresourcesgate/cache_test.go

@@ -0,0 +1,251 @@
+/*
+Copyright 2025 The Crossplane 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 customresourcesgate
+
+import (
+	"testing"
+
+	"github.com/google/go-cmp/cmp"
+	"github.com/google/go-cmp/cmp/cmpopts"
+	apiextensionsv1 "k8s.io/apiextensions-apiserver/pkg/apis/apiextensions/v1"
+	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+)
+
+func TestTransformStripCRDSchema(t *testing.T) {
+	type args struct {
+		obj any
+	}
+
+	type want struct {
+		obj any
+		err error
+	}
+
+	cases := map[string]struct {
+		reason string
+		args   args
+		want   want
+	}{
+		"StripsSchemaManagedFieldsAndAnnotation": {
+			reason: "Should strip OpenAPI schemas, ManagedFields, and last-applied-configuration annotation",
+			args: args{
+				obj: &apiextensionsv1.CustomResourceDefinition{
+					ObjectMeta: metav1.ObjectMeta{
+						Name: "testresources.example.com",
+						Annotations: map[string]string{
+							"kubectl.kubernetes.io/last-applied-configuration": `{"very":"large","json":"blob"}`,
+							"other-annotation": "keep-me",
+						},
+						ManagedFields: []metav1.ManagedFieldsEntry{
+							{Manager: "kubectl", Operation: metav1.ManagedFieldsOperationApply},
+						},
+					},
+					Spec: apiextensionsv1.CustomResourceDefinitionSpec{
+						Group: "example.com",
+						Names: apiextensionsv1.CustomResourceDefinitionNames{Kind: "TestResource"},
+						Versions: []apiextensionsv1.CustomResourceDefinitionVersion{
+							{
+								Name:   "v1",
+								Served: true,
+								Schema: &apiextensionsv1.CustomResourceValidation{
+									OpenAPIV3Schema: &apiextensionsv1.JSONSchemaProps{
+										Type: "object",
+										Properties: map[string]apiextensionsv1.JSONSchemaProps{
+											"spec": {Type: "object"},
+										},
+									},
+								},
+							},
+						},
+					},
+					Status: apiextensionsv1.CustomResourceDefinitionStatus{
+						Conditions: []apiextensionsv1.CustomResourceDefinitionCondition{
+							{
+								Type:   apiextensionsv1.Established,
+								Status: apiextensionsv1.ConditionTrue,
+							},
+						},
+					},
+				},
+			},
+			want: want{
+				obj: &apiextensionsv1.CustomResourceDefinition{
+					ObjectMeta: metav1.ObjectMeta{
+						Name: "testresources.example.com",
+						Annotations: map[string]string{
+							"other-annotation": "keep-me",
+						},
+					},
+					Spec: apiextensionsv1.CustomResourceDefinitionSpec{
+						Group: "example.com",
+						Names: apiextensionsv1.CustomResourceDefinitionNames{Kind: "TestResource"},
+						Versions: []apiextensionsv1.CustomResourceDefinitionVersion{
+							{
+								Name:   "v1",
+								Served: true,
+								Schema: nil,
+							},
+						},
+					},
+					Status: apiextensionsv1.CustomResourceDefinitionStatus{
+						Conditions: []apiextensionsv1.CustomResourceDefinitionCondition{
+							{
+								Type:   apiextensionsv1.Established,
+								Status: apiextensionsv1.ConditionTrue,
+							},
+						},
+					},
+				},
+			},
+		},
+		"MultipleVersions": {
+			reason: "Should strip schemas from all versions",
+			args: args{
+				obj: &apiextensionsv1.CustomResourceDefinition{
+					Spec: apiextensionsv1.CustomResourceDefinitionSpec{
+						Group: "example.com",
+						Names: apiextensionsv1.CustomResourceDefinitionNames{Kind: "TestResource"},
+						Versions: []apiextensionsv1.CustomResourceDefinitionVersion{
+							{
+								Name:   "v1",
+								Served: true,
+								Schema: &apiextensionsv1.CustomResourceValidation{
+									OpenAPIV3Schema: &apiextensionsv1.JSONSchemaProps{Type: "object"},
+								},
+							},
+							{
+								Name:   "v1beta1",
+								Served: false,
+								Schema: &apiextensionsv1.CustomResourceValidation{
+									OpenAPIV3Schema: &apiextensionsv1.JSONSchemaProps{Type: "object"},
+								},
+							},
+						},
+					},
+				},
+			},
+			want: want{
+				obj: &apiextensionsv1.CustomResourceDefinition{
+					Spec: apiextensionsv1.CustomResourceDefinitionSpec{
+						Group: "example.com",
+						Names: apiextensionsv1.CustomResourceDefinitionNames{Kind: "TestResource"},
+						Versions: []apiextensionsv1.CustomResourceDefinitionVersion{
+							{Name: "v1", Served: true, Schema: nil},
+							{Name: "v1beta1", Served: false, Schema: nil},
+						},
+					},
+				},
+			},
+		},
+		"NoVersions": {
+			reason: "Should handle CRD with no versions without panicking",
+			args: args{
+				obj: &apiextensionsv1.CustomResourceDefinition{
+					Spec: apiextensionsv1.CustomResourceDefinitionSpec{
+						Group: "example.com",
+						Names: apiextensionsv1.CustomResourceDefinitionNames{Kind: "TestResource"},
+					},
+				},
+			},
+			want: want{
+				obj: &apiextensionsv1.CustomResourceDefinition{
+					Spec: apiextensionsv1.CustomResourceDefinitionSpec{
+						Group: "example.com",
+						Names: apiextensionsv1.CustomResourceDefinitionNames{Kind: "TestResource"},
+					},
+				},
+			},
+		},
+		"NilAnnotations": {
+			reason: "Should handle CRD with nil annotations map without panicking",
+			args: args{
+				obj: &apiextensionsv1.CustomResourceDefinition{
+					ObjectMeta: metav1.ObjectMeta{
+						Name: "test.example.com",
+					},
+					Spec: apiextensionsv1.CustomResourceDefinitionSpec{
+						Group: "example.com",
+						Names: apiextensionsv1.CustomResourceDefinitionNames{Kind: "TestResource"},
+					},
+				},
+			},
+			want: want{
+				obj: &apiextensionsv1.CustomResourceDefinition{
+					ObjectMeta: metav1.ObjectMeta{
+						Name: "test.example.com",
+					},
+					Spec: apiextensionsv1.CustomResourceDefinitionSpec{
+						Group: "example.com",
+						Names: apiextensionsv1.CustomResourceDefinitionNames{Kind: "TestResource"},
+					},
+				},
+			},
+		},
+		"NoLastAppliedAnnotation": {
+			reason: "Should leave other annotations intact when last-applied-configuration is absent",
+			args: args{
+				obj: &apiextensionsv1.CustomResourceDefinition{
+					ObjectMeta: metav1.ObjectMeta{
+						Annotations: map[string]string{
+							"custom-annotation": "value",
+						},
+					},
+					Spec: apiextensionsv1.CustomResourceDefinitionSpec{
+						Group: "example.com",
+						Names: apiextensionsv1.CustomResourceDefinitionNames{Kind: "TestResource"},
+					},
+				},
+			},
+			want: want{
+				obj: &apiextensionsv1.CustomResourceDefinition{
+					ObjectMeta: metav1.ObjectMeta{
+						Annotations: map[string]string{
+							"custom-annotation": "value",
+						},
+					},
+					Spec: apiextensionsv1.CustomResourceDefinitionSpec{
+						Group: "example.com",
+						Names: apiextensionsv1.CustomResourceDefinitionNames{Kind: "TestResource"},
+					},
+				},
+			},
+		},
+		"NonCRDObject": {
+			reason: "Should return non-CRD objects unchanged",
+			args: args{
+				obj: "not-a-crd",
+			},
+			want: want{
+				obj: "not-a-crd",
+			},
+		},
+	}
+
+	for name, tc := range cases {
+		t.Run(name, func(t *testing.T) {
+			got, err := TransformStripCRDSchema(tc.args.obj)
+
+			if diff := cmp.Diff(tc.want.err, err, cmpopts.EquateErrors()); diff != "" {
+				t.Errorf("%s\nTransformStripCRDSchema(...): -want error, +got error:\n%s", tc.reason, diff)
+			}
+
+			if diff := cmp.Diff(tc.want.obj, got); diff != "" {
+				t.Errorf("%s\nTransformStripCRDSchema(...): -want, +got:\n%s", tc.reason, diff)
+			}
+		})
+	}
+}