nfd-topology-updater: add metrics support

For now, add only one metric, a counter for the errors occurring while
scanning pod resources on the node.

cmd/nfd-topology-updater/main.go

@@ -106,6 +106,8 @@ func initFlags(flagset *flag.FlagSet) (*topology.Args, *resourcemonitor.Args) {
 		"Do not publish discovered features to the cluster-local Kubernetes API server.")
 	flagset.StringVar(&args.KubeConfigFile, "kubeconfig", "",
 		"Kube config file.")
+	flagset.IntVar(&args.MetricsPort, "metrics", 8081,
+		"Port on which to expose metrics.")
 	flagset.DurationVar(&resourcemonitorArgs.SleepInterval, "sleep-interval", time.Duration(60)*time.Second,
 		"Time to sleep between CR updates. zero means no CR updates on interval basis. [Default: 60s]")
 	flagset.StringVar(&resourcemonitorArgs.Namespace, "watch-namespace", "*",

deployment/base/topologyupdater-daemonset/topologyupdater-daemonset.yaml

@@ -22,3 +22,6 @@ spec:
           command:
             - "nfd-topology-updater"
           args: []
+          ports:
+            - name: metrics
+              containerPort: 8081

deployment/helm/node-feature-discovery/templates/topologyupdater.yaml

@@ -70,6 +70,10 @@ spec:
           # Disable kubelet state tracking by giving an empty path
           - "-kubelet-state-dir="
           {{- end }}
+          - -metrics={{ .Values.topologyUpdater.metricsPort | default "8081"}}
+        ports:
+          - name: metrics
+            containerPort: {{ .Values.topologyUpdater.metricsPort | default "8081"}}
         volumeMounts:
         {{- if .Values.topologyUpdater.kubeletConfigPath | empty | not }}
         - name: kubelet-config

deployment/helm/node-feature-discovery/values.yaml

@@ -417,6 +417,7 @@ topologyUpdater:
   rbac:
     create: true
 
+  metricsPort: 8081
   kubeletConfigPath:
   kubeletPodResourcesSockPath:
   updateInterval: 60s

docs/deployment/helm.md

@@ -173,6 +173,7 @@ API's you need to install the prometheus operator in your cluster.
 | `topologyUpdater.serviceAccount.annotations`  | dict   | {}                      | Annotations to add to the service account for topology updater                                                                                                                                        |
 | `topologyUpdater.serviceAccount.name`         | string |                         | The name of the service account for topology updater to use. If not set and create is true, a name is generated using the fullname template and `-topology-updater` suffix                            |
 | `topologyUpdater.rbac.create`                 | bool   | true                    | Specifies whether to create [RBAC][rbac] configuration for topology updater                                                                                                                           |
+| `topologyUpdater.metricsPort`                 | integer | 8081                   | Port on which to expose prometheus metrics |
 | `topologyUpdater.kubeletConfigPath`           | string | ""                      | Specifies the kubelet config host path                                                                                                                                                                |
 | `topologyUpdater.kubeletPodResourcesSockPath` | string | ""                      | Specifies the kubelet sock path to read pod resources                                                                                                                                                 |
 | `topologyUpdater.updateInterval`              | string | 60s                     | Time to sleep between CR updates. Non-positive value implies no CR update.                                                                                                                            |

docs/deployment/metrics.md

@@ -20,6 +20,7 @@ The exposed metrics are
 | `nfd_node_updates_total`                          | Counter   | Number of nodes updated
 | `nfd_nodefeaturerule_processing_duration_seconds` | Histogram | Time taken to process NodeFeatureRule objects
 | `nfd_feature_discovery_duration_seconds`          | Histogram | Time taken to discover features on a node
+| `nfd_topology_updater_scan_errors_total`          | Counter   | Number of errors in scanning resource allocation of pods.
 
 ## Via Kustomize
 

docs/reference/topology-updater-commandline-reference.md

@@ -72,6 +72,20 @@ Example:
 nfd-topology-updater -oneshot -no-publish
 ```
 
+### -metrics
+
+The `-metrics` flag specifies the port on which to expose
+[Prometheus](https://prometheus.io/) metrics. Setting this to 0 disables the
+metrics server on nfd-topology-updater.
+
+Default: 8081
+
+Example:
+
+```bash
+nfd-topology-updater -metrics=12345
+```
+
 ### -sleep-interval
 
 The `-sleep-interval` specifies the interval between resource hardware

pkg/nfd-topology-updater/metrics.go

@@ -0,0 +1,75 @@
+/*
+Copyright 2023 The Kubernetes 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 nfdtopologyupdater
+
+import (
+	"fmt"
+	"net/http"
+
+	"github.com/prometheus/client_golang/prometheus"
+	"github.com/prometheus/client_golang/prometheus/promhttp"
+	"k8s.io/klog/v2"
+	"sigs.k8s.io/node-feature-discovery/pkg/version"
+)
+
+// When adding metric names, see https://prometheus.io/docs/practices/naming/#metric-names
+const (
+	buildInfoQuery  = "nfd_topology_updater_build_info"
+	scanErrorsQuery = "nfd_topology_updater_scan_errors_total"
+)
+
+var (
+	srv *http.Server
+
+	buildInfo = prometheus.NewGauge(prometheus.GaugeOpts{
+		Name: buildInfoQuery,
+		Help: "Version from which Node Feature Discovery was built.",
+		ConstLabels: map[string]string{
+			"version": version.Get(),
+		},
+	})
+	scanErrors = prometheus.NewCounter(prometheus.CounterOpts{
+		Name: scanErrorsQuery,
+		Help: "Number of errors in scanning resource allocation of pods.",
+	})
+)
+
+// registerVersion exposes the Operator build version.
+func registerVersion(version string) {
+	buildInfo.SetToCurrentTime()
+}
+
+// runMetricsServer starts a http server to expose metrics
+func runMetricsServer(port int) {
+	r := prometheus.NewRegistry()
+	r.MustRegister(buildInfo,
+		scanErrors)
+	mux := http.NewServeMux()
+	mux.Handle("/metrics", promhttp.HandlerFor(r, promhttp.HandlerOpts{}))
+
+	klog.InfoS("metrics server starting", "port", port)
+	srv = &http.Server{Addr: fmt.Sprintf(":%d", port), Handler: mux}
+	klog.InfoS("metrics server stopped", "exitCode", srv.ListenAndServe())
+}
+
+// stopMetricsServer stops the metrics server
+func stopMetricsServer() {
+	if srv != nil {
+		klog.InfoS("stopping metrics server", "port", srv.Addr)
+		srv.Close()
+	}
+}

pkg/nfd-topology-updater/nfd-topology-updater.go

@@ -50,6 +50,7 @@ const (
 
 // Args are the command line arguments
 type Args struct {
+	MetricsPort     int
 	NoPublish       bool
 	Oneshot         bool
 	KubeConfigFile  string
@@ -142,6 +143,13 @@ func (w *nfdTopologyUpdater) Run() error {
 		return fmt.Errorf("faild to configure Node Feature Discovery Topology Updater: %w", err)
 	}
 
+	// Register to metrics server
+	if w.args.MetricsPort > 0 {
+		go runMetricsServer(w.args.MetricsPort)
+		registerVersion(version.Get())
+		defer stopMetricsServer()
+	}
+
 	var resScan resourcemonitor.ResourcesScanner
 
 	resScan, err = resourcemonitor.NewPodResourcesScanner(w.resourcemonitorArgs.Namespace, podResClient, w.apihelper, w.resourcemonitorArgs.PodSetFingerprint)
@@ -169,6 +177,7 @@ func (w *nfdTopologyUpdater) Run() error {
 			klog.V(1).InfoS("received updated pod resources", "podResources", utils.DelayedDumper(scanResponse.PodResources))
 			if err != nil {
 				klog.ErrorS(err, "scan failed")
+				scanErrors.Inc()
 				continue
 			}
 			zones = resAggr.Aggregate(scanResponse.PodResources)