[CONTINT-4416] Optimize KSM configmap collection (#32368)

pkg/kubestatemetrics/builder/builder.go

@@ -9,6 +9,7 @@ package builder
 
 import (
 	"context"
+	"fmt"
 	"reflect"
 	"time"
 
@@ -18,7 +19,11 @@ import (
 	v1 "k8s.io/apimachinery/pkg/apis/meta/v1"
 	"k8s.io/apimachinery/pkg/apis/meta/v1/unstructured"
 	"k8s.io/apimachinery/pkg/runtime"
+	"k8s.io/apimachinery/pkg/runtime/schema"
+	apiwatch "k8s.io/apimachinery/pkg/watch"
 	clientset "k8s.io/client-go/kubernetes"
+	"k8s.io/client-go/metadata"
+	"k8s.io/client-go/rest"
 	"k8s.io/client-go/tools/cache"
 	ksmbuild "k8s.io/kube-state-metrics/v2/pkg/builder"
 	ksmtypes "k8s.io/kube-state-metrics/v2/pkg/builder/types"
@@ -196,6 +201,14 @@ func GenerateStores[T any](
 		isPod = true
 	} else if u, ok := expectedType.(*unstructured.Unstructured); ok {
 		isPod = u.GetAPIVersion() == "v1" && u.GetKind() == "Pod"
+	} else if _, ok := expectedType.(*corev1.ConfigMap); ok {
+		configMapStore, err := generateConfigMapStores(b, metricFamilies, useAPIServerCache)
+		if err != nil {
+			log.Debugf("Defaulting to kube-state-metrics for configmap collection: %v", err)
+		} else {
+			log.Debug("Using meta.k8s.io API for configmap collection")
+			return configMapStore
+		}
 	}
 
 	if b.namespaces.IsAllNamespaces() {
@@ -340,3 +353,101 @@ func handlePodCollection[T any](b *Builder, store cache.Store, client T, listWat
 	listWatcher := listWatchFunc(client, namespace, fieldSelector)
 	b.startReflector(&corev1.Pod{}, store, listWatcher, useAPIServerCache)
 }
+
+func generateConfigMapStores(
+	b *Builder,
+	metricFamilies []generator.FamilyGenerator,
+	useAPIServerCache bool,
+) ([]cache.Store, error) {
+	restConfig, err := rest.InClusterConfig()
+	if err != nil {
+		return nil, fmt.Errorf("failed to create in-cluster config for metadata client: %w", err)
+	}
+
+	metadataClient, err := metadata.NewForConfig(restConfig)
+	if err != nil {
+		return nil, fmt.Errorf("failed to create metadata client: %w", err)
+	}
+
+	gvr := schema.GroupVersionResource{
+		Group:    "",
+		Version:  "v1",
+		Resource: "configmaps",
+	}
+
+	filteredMetricFamilies := generator.FilterFamilyGenerators(b.allowDenyList, metricFamilies)
+	composedMetricGenFuncs := generator.ComposeMetricGenFuncs(filteredMetricFamilies)
+
+	stores := make([]cache.Store, 0)
+
+	if b.namespaces.IsAllNamespaces() {
+		log.Infof("Using NamespaceAll for ConfigMap collection.")
+		store := store.NewMetricsStore(composedMetricGenFuncs, "configmap")
+		listWatcher := createConfigMapListWatch(metadataClient, gvr, v1.NamespaceAll)
+		b.startReflector(&corev1.ConfigMap{}, store, listWatcher, useAPIServerCache)
+		return []cache.Store{store}, nil
+	}
+
+	for _, ns := range b.namespaces {
+		store := store.NewMetricsStore(composedMetricGenFuncs, "configmap")
+		listWatcher := createConfigMapListWatch(metadataClient, gvr, ns)
+		b.startReflector(&corev1.ConfigMap{}, store, listWatcher, useAPIServerCache)
+		stores = append(stores, store)
+	}
+
+	return stores, nil
+}
+
+func createConfigMapListWatch(metadataClient metadata.Interface, gvr schema.GroupVersionResource, namespace string) *cache.ListWatch {
+	return &cache.ListWatch{
+		ListFunc: func(options v1.ListOptions) (runtime.Object, error) {
+			result, err := metadataClient.Resource(gvr).Namespace(namespace).List(context.TODO(), options)
+			if err != nil {
+				return nil, err
+			}
+
+			configMapList := &corev1.ConfigMapList{}
+			for _, item := range result.Items {
+				configMapList.Items = append(configMapList.Items, corev1.ConfigMap{
+					ObjectMeta: v1.ObjectMeta{
+						Name:            item.GetName(),
+						Namespace:       item.GetNamespace(),
+						UID:             item.GetUID(),
+						ResourceVersion: item.GetResourceVersion(),
+					},
+				})
+			}
+
+			return configMapList, nil
+		},
+		WatchFunc: func(options v1.ListOptions) (apiwatch.Interface, error) {
+			watcher, err := metadataClient.Resource(gvr).Namespace(namespace).Watch(context.TODO(), options)
+			if err != nil {
+				return nil, err
+			}
+
+			return apiwatch.Filter(watcher, func(event apiwatch.Event) (apiwatch.Event, bool) {
+				if event.Object == nil {
+					return event, false
+				}
+
+				partialObject, ok := event.Object.(*v1.PartialObjectMetadata)
+				if !ok {
+					return event, false
+				}
+
+				configMap := &corev1.ConfigMap{
+					ObjectMeta: v1.ObjectMeta{
+						Name:            partialObject.GetName(),
+						Namespace:       partialObject.GetNamespace(),
+						UID:             partialObject.GetUID(),
+						ResourceVersion: partialObject.GetResourceVersion(),
+					},
+				}
+
+				event.Object = configMap
+				return event, true
+			}), nil
+		},
+	}
+}

releasenotes-dca/notes/optimize-ksm-configmap-collection-dcd3bfaa71fb2865.yaml

@@ -0,0 +1,13 @@
+# Each section from every release note are combined when the
+# CHANGELOG-DCA.rst is rendered. So the text needs to be worded so that
+# it does not depend on any information only available in another
+# section. This may mean repeating some details, but each section
+# must be readable independently of the other.
+#
+# Each section note must be formatted as reStructuredText.
+---
+enhancements:
+  - |
+    The `kubernetes_state_core` check now collects only metadata for configmaps,
+    reducing memory, CPU, and network usage in the Cluster Agent while preserving
+    full metric functionality.