Improve metadata comparison: We should not only filter out the resourceVersion, but also a few other fields managed by the cluster

Author: Moritz Clasmeier

pkg/reconciler/internal/updater/updater.go

@@ -197,8 +197,8 @@ func (u *Updater) Apply(ctx context.Context, baseObj *unstructured.Unstructured)
 
 func isSafeForUpdate(logger logr.Logger, inMemory *unstructured.Unstructured, onCluster *unstructured.Unstructured) bool {
 	// Compare metadata (excluding resourceVersion).
-	inMemoryMetadata := metadataWithoutResourceVersion(inMemory)
-	onClusterMetadata := metadataWithoutResourceVersion(onCluster)
+	inMemoryMetadata := reducedMetadata(inMemory)
+	onClusterMetadata := reducedMetadata(onCluster)
 	if !reflect.DeepEqual(inMemoryMetadata, onClusterMetadata) {
 		// Diff in metadata. Nothing we can do about it -> Fail.
 		logger.V(1).Info("Not refreshing object due to metadata mismatch",
@@ -221,21 +221,42 @@ func isSafeForUpdate(logger logr.Logger, inMemory *unstructured.Unstructured, on
 	return true
 }
 
-func metadataWithoutResourceVersion(u *unstructured.Unstructured) map[string]interface{} {
+// recudedMetadata returns the metadata of the given unstructured object,
+// excluding a couple of fields which should not be taken into account
+// for equality checks. The excluded fields are:
+//
+//   - metadata.resourceVersion
+//   - metadata.managedFields
+//   - metadata.annotation."kubectl.kubernetes.io/last-applied-configuration"
+func reducedMetadata(u *unstructured.Unstructured) map[string]interface{} {
 	metadata, ok := u.Object["metadata"].(map[string]interface{})
 	if !ok {
 		return nil
 	}
-	modifiedMetadata := make(map[string]interface{}, len(metadata))
-	for k, v := range metadata {
-		if k == "resourceVersion" {
-			continue
-		}
-		modifiedMetadata[k] = v
+	modifiedMetadata := excludeFromMap(metadata, "resourceVersion", "managedFields")
+	if annotations, found := modifiedMetadata["annotations"].(map[string]interface{}); found {
+		modifiedMetadata["annotations"] = excludeFromMap(annotations, "kubectl.kubernetes.io/last-applied-configuration")
 	}
+
 	return modifiedMetadata
 }
 
+// excludeFromMap returns a new map that contains all key-value pairs from inputMap
+// except those whose keys are in the keys slice.
+func excludeFromMap(inputMap map[string]interface{}, keys ...string) map[string]interface{} {
+	resultMap := make(map[string]interface{}, len(inputMap))
+	excludeKeys := make(map[string]struct{})
+	for _, k := range keys {
+		excludeKeys[k] = struct{}{}
+	}
+	for k, v := range inputMap {
+		if _, found := excludeKeys[k]; !found {
+			resultMap[k] = v
+		}
+	}
+	return resultMap
+}
+
 func (u *Updater) tryRefresh(ctx context.Context, obj *unstructured.Unstructured) (bool, error) {
 	// Re-fetch object with client.
 	current := &unstructured.Unstructured{}