Add new metric to expose GKE component version

Author: saikat-royc

cmd/gce-pd-csi-driver/main.go

@@ -28,6 +28,7 @@ import (
 	gce "sigs.k8s.io/gcp-compute-persistent-disk-csi-driver/pkg/gce-cloud-provider/compute"
 	metadataservice "sigs.k8s.io/gcp-compute-persistent-disk-csi-driver/pkg/gce-cloud-provider/metadata"
 	driver "sigs.k8s.io/gcp-compute-persistent-disk-csi-driver/pkg/gce-pd-csi-driver"
+	"sigs.k8s.io/gcp-compute-persistent-disk-csi-driver/pkg/metrics"
 	mountmanager "sigs.k8s.io/gcp-compute-persistent-disk-csi-driver/pkg/mount-manager"
 )
 
@@ -36,6 +37,8 @@ var (
 	endpoint             = flag.String("endpoint", "unix:/tmp/csi.sock", "CSI endpoint")
 	runControllerService = flag.Bool("run-controller-service", true, "If set to false then the CSI driver does not activate its controller service (default: true)")
 	runNodeService       = flag.Bool("run-node-service", true, "If set to false then the CSI driver does not activate its node service (default: true)")
+	httpEndpoint         = flag.String("http-endpoint", "", "The TCP network address where the prometheus metrics endpoint will listen (example: `:8080`). The default is empty string, which means metrics endpoint is disabled.")
+	metricsPath          = flag.String("metrics-path", "/metrics", "The HTTP path where prometheus metrics will be exposed. Default is `/metrics`.")
 	extraVolumeLabels    map[string]string
 	version              string
 )
@@ -70,6 +73,11 @@ func handle() {
 	}
 	klog.V(2).Infof("Driver vendor version %v", version)
 
+	if *runControllerService && *httpEndpoint != "" && metrics.IsComponentVersionAvailable() {
+		metrics.InitializeHandler(*httpEndpoint, *metricsPath)
+		metrics.RegisterComponentVersionMetric()
+	}
+
 	gceDriver := driver.GetGCEDriver()
 
 	//Initialize GCE Driver

go.mod

@@ -13,6 +13,7 @@ require (
 	github.com/kubernetes-csi/csi-test/v3 v3.0.0
 	github.com/onsi/ginkgo v1.11.0
 	github.com/onsi/gomega v1.7.1
+	github.com/prometheus/client_golang v1.0.0
 	golang.org/x/net v0.0.0-20201021035429-f5854403a974 // indirect
 	golang.org/x/oauth2 v0.0.0-20200902213428-5d25da1a8d43
 	golang.org/x/sys v0.0.0-20200930185726-fdedc70b468f

pkg/metrics/metrics.go

@@ -0,0 +1,84 @@
+/*
+Copyright 2020 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 metrics
+
+import (
+	"net/http"
+	"os"
+
+	"github.com/prometheus/client_golang/prometheus"
+	"github.com/prometheus/client_golang/prometheus/promhttp"
+	"k8s.io/klog"
+)
+
+const (
+	// envPDCSIVersion is an environment variable set in the PDCSI controller manifest
+	// with the current version of the GKE component.
+	envPDCSIVersion = "PDCSI_VERSION"
+)
+
+var (
+	// This metric is exposed only from the controller driver component when PDCSI_VERSION env variable is set.
+	componentVersion = prometheus.NewGaugeVec(
+		prometheus.GaugeOpts{
+			Name: "component_version",
+			Help: "Metric to expose the version of the PDCSI GKE component.",
+		},
+		[]string{"component_version"},
+	)
+)
+
+func InitializeHandler(address, path string) {
+	go func() {
+		http.Handle("/metrics", promhttp.Handler())
+		err := http.ListenAndServe(address, nil)
+		klog.Fatalf("Failed to start metrics handler: %v", err)
+	}()
+}
+
+func RegisterComponentVersionMetric() {
+	v := getEnvVar(envPDCSIVersion)
+	if v == "" {
+		klog.V(2).Info("Skip emitting component version metric")
+		return
+	}
+
+	prometheus.MustRegister(componentVersion)
+	recordMetric(componentVersion, v)
+}
+
+func recordMetric(metric *prometheus.GaugeVec, value string) {
+	metric.WithLabelValues(value).Set(1.0)
+}
+
+func getEnvVar(envVarName string) string {
+	v, ok := os.LookupEnv(envVarName)
+	if !ok {
+		klog.Warningf("%q env not set", envVarName)
+		return ""
+	}
+
+	return v
+}
+
+func IsComponentVersionAvailable() bool {
+	if getEnvVar(envPDCSIVersion) == "" {
+		return false
+	}
+
+	return true
+}