Only watch metadata for ReplicaSets in K8s provider (#5699)

Use a metadata informer for ReplicaSets.
Use a transform function to drop all data except for the owner
references, which we need to find the Deployment name.

(cherry picked from commit 05f9e81)

changelog/fragments/1728039144-k8s-replicaset-onlymeta.yaml

@@ -0,0 +1,32 @@
+# Kind can be one of:
+# - breaking-change: a change to previously-documented behavior
+# - deprecation: functionality that is being removed in a later release
+# - bug-fix: fixes a problem in a previous version
+# - enhancement: extends functionality but does not break or fix existing behavior
+# - feature: new functionality
+# - known-issue: problems that we are aware of in a given version
+# - security: impacts on the security of a product or a user’s deployment.
+# - upgrade: important information for someone upgrading from a prior version
+# - other: does not fit into any of the other categories
+kind: enhancement
+
+# Change summary; a 80ish characters long description of the change.
+summary: Only watch metadata for ReplicaSets in K8s provider
+
+# Long description; in case the summary is not enough to describe the change
+# this field accommodate a description without length limits.
+# NOTE: This field will be rendered only for breaking-change and known-issue kinds at the moment.
+#description:
+
+# Affected component; usually one of "elastic-agent", "fleet-server", "filebeat", "metricbeat", "auditbeat", "all", etc.
+component: elastic-agent
+
+# PR URL; optional; the PR number that added the changeset.
+# If not present is automatically filled by the tooling finding the PR where this changelog fragment has been added.
+# NOTE: the tooling supports backports, so it's able to fill the original PR number instead of the backport PR number.
+# Please provide it if you are adding a fragment for a different PR.
+#pr: https://github.com/owner/repo/1234
+
+# Issue URL; optional; the GitHub issue related to this changeset (either closes or is part of).
+# If not present is automatically filled by the tooling with the issue linked to the PR number.
+#issue: https://github.com/owner/repo/1234

internal/pkg/composable/providers/kubernetes/pod.go

@@ -9,6 +9,8 @@ import (
 	"sync"
 	"time"
 
+	"k8s.io/apimachinery/pkg/runtime/schema"
+
 	"github.com/elastic/elastic-agent-autodiscover/kubernetes"
 	"github.com/elastic/elastic-agent-autodiscover/kubernetes/metadata"
 	"github.com/elastic/elastic-agent-autodiscover/utils"
@@ -104,11 +106,21 @@ func NewPodEventer(
 	// Deployment -> Replicaset -> Pod
 	// CronJob -> job -> Pod
 	if metaConf.Deployment {
-		replicaSetWatcher, err = kubernetes.NewNamedWatcher("resource_metadata_enricher_rs", client, &kubernetes.ReplicaSet{}, kubernetes.WatchOptions{
-			SyncTimeout:  cfg.SyncPeriod,
-			Namespace:    cfg.Namespace,
-			HonorReSyncs: true,
-		}, nil)
+		metadataClient, err := kubernetes.GetKubernetesMetadataClient(cfg.KubeConfig, cfg.KubeClientOptions)
+		if err != nil {
+			logger.Errorf("Error creating metadata client for %T due to error %+v", &kubernetes.Namespace{}, err)
+		}
+		// use a custom watcher here, so we can provide a transform function and limit the data we're storing
+		replicaSetWatcher, err = kubernetes.NewNamedMetadataWatcher(
+			"resource_metadata_enricher_rs",
+			client,
+			metadataClient,
+			schema.GroupVersionResource{Group: "apps", Version: "v1", Resource: "replicasets"},
+			kubernetes.WatchOptions{
+				SyncTimeout:  cfg.SyncPeriod,
+				Namespace:    cfg.Namespace,
+				HonorReSyncs: true,
+			}, nil, metadata.RemoveUnnecessaryReplicaSetData)
 		if err != nil {
 			logger.Errorf("Error creating watcher for %T due to error %+v", &kubernetes.Namespace{}, err)
 		}