Add cluster level add_kubernetes_metadata support for centralized enrichment

CHANGELOG.next.asciidoc

@@ -503,6 +503,7 @@ https://github.com/elastic/beats/compare/v7.0.0-alpha2...master[Check the HEAD d
 - Kafka is now supported up to version 2.8.0. {pull}27720[27720]
 - Add Huawei Cloud provider to add_cloud_metadata. {pull}27607[27607]
 - Add default seccomp policy for linux arm64. {pull}27955[27955]
+- Add cluster level add_kubernetes_metadata support for centralized enrichment {pull}24621[24621]
 
 *Auditbeat*
 

libbeat/processors/add_kubernetes_metadata/config.go

@@ -18,6 +18,7 @@
 package add_kubernetes_metadata
 
 import (
+	"fmt"
 	"time"
 
 	"github.com/elastic/beats/v7/libbeat/common"
@@ -27,6 +28,7 @@ import (
 type kubeAnnotatorConfig struct {
 	KubeConfig string        `config:"kube_config"`
 	Host       string        `config:"host"`
+	Scope      string        `config:"scope"`
 	Namespace  string        `config:"namespace"`
 	SyncPeriod time.Duration `config:"sync_period"`
 	// Annotations are kept after pod is removed, until they haven't been accessed
@@ -52,5 +54,18 @@ func defaultKubernetesAnnotatorConfig() kubeAnnotatorConfig {
 		CleanupTimeout:  60 * time.Second,
 		DefaultMatchers: Enabled{true},
 		DefaultIndexers: Enabled{true},
+		Scope:           "node",
 	}
 }
+
+func (k *kubeAnnotatorConfig) Validate() error {
+	if k.Scope != "node" && k.Scope != "cluster" {
+		return fmt.Errorf("invalid scope %s, valid values include `cluster`, `node`", k.Scope)
+	}
+
+	if k.Scope == "cluster" {
+		k.Host = ""
+	}
+
+	return nil
+}

libbeat/processors/add_kubernetes_metadata/config_test.go

@@ -0,0 +1,62 @@
+// Licensed to Elasticsearch B.V. under one or more contributor
+// license agreements. See the NOTICE file distributed with
+// this work for additional information regarding copyright
+// ownership. Elasticsearch B.V. licenses this file to you 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 add_kubernetes_metadata
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/require"
+
+	"github.com/elastic/beats/v7/libbeat/common"
+)
+
+func TestConfigValidate(t *testing.T) {
+	tests := []struct {
+		cfg   map[string]interface{}
+		error bool
+	}{
+		{
+			cfg: map[string]interface{}{
+				"scope": "foo",
+			},
+			error: true,
+		},
+		{
+			cfg: map[string]interface{}{
+				"scope": "cluster",
+			},
+			error: false,
+		},
+		{
+			cfg:   map[string]interface{}{},
+			error: false,
+		},
+	}
+
+	for _, test := range tests {
+		cfg := common.MustNewConfigFrom(test.cfg)
+		c := defaultKubernetesAnnotatorConfig()
+
+		err := cfg.Unpack(&c)
+		if test.error {
+			require.NotNil(t, err)
+		} else {
+			require.Nil(t, err)
+		}
+	}
+}

libbeat/processors/add_kubernetes_metadata/docs/add_kubernetes_metadata.asciidoc

@@ -115,6 +115,8 @@ The `add_kubernetes_metadata` processor has the following configuration settings
 `host`:: (Optional) Specify the node to scope {beatname_lc} to in case it
 cannot be accurately detected, as when running {beatname_lc} in host network
 mode.
+`scope`:: (Optional) Specify if the processor should have visibility at the node level or at the entire cluster
+level. Possible values are `node` and `cluster`. Scope is `node` by default.
 `namespace`:: (Optional) Select the namespace from which to collect the
 metadata. If it is not set, the processor collects metadata from all namespaces.
 It is unset by default.

libbeat/processors/add_kubernetes_metadata/kubernetes.go

@@ -170,12 +170,14 @@ func (k *kubernetesAnnotator) init(config kubeAnnotatorConfig, cfg *common.Confi
 			IsInCluster: kubernetes.IsInCluster(config.KubeConfig),
 			HostUtils:   &kubernetes.DefaultDiscoveryUtils{},
 		}
-		config.Host, err = kubernetes.DiscoverKubernetesNode(k.log, nd)
-		if err != nil {
-			k.log.Errorf("Couldn't discover Kubernetes node: %w", err)
-			return
+		if config.Scope == "node" {
+			config.Host, err = kubernetes.DiscoverKubernetesNode(k.log, nd)
+			if err != nil {
+				k.log.Errorf("Couldn't discover Kubernetes node: %w", err)
+				return
+			}
+			k.log.Debugf("Initializing a new Kubernetes watcher using host: %s", config.Host)
 		}
-		k.log.Debugf("Initializing a new Kubernetes watcher using host: %s", config.Host)
 
 		watcher, err := kubernetes.NewWatcher(client, &kubernetes.Pod{}, kubernetes.WatchOptions{
 			SyncTimeout: config.SyncPeriod,