add prometheus metric

Signed-off-by: Gang Li <ganglica@google.com>
Signed-off-by: Gang Li <gangligit@gmail.com>

pkg/featuregate/feature_gate.go

@@ -112,8 +112,6 @@ type MutableFeatureGate interface {
 	Add(features map[Feature]FeatureSpec) error
 	// GetAll returns a copy of the map of known feature names to feature specs.
 	GetAll() map[Feature]FeatureSpec
-	// AddMetrics adds feature enablement metrics
-	AddMetrics()
 	// OverrideDefault sets a local override for the registered default value of a named
 	// feature. If the feature has not been previously registered (e.g. by a call to Add), has a
 	// locked default, or if the gate has already registered itself with a FlagSet, a non-nil
@@ -363,10 +361,6 @@ func (f *featureGate) AddFlag(fs *flag.FlagSet, flagName string) {
 		"Options are:\n"+strings.Join(known, "\n"))
 }
 
-func (f *featureGate) AddMetrics() {
-	// TODO(henrybear327): implement this.
-}
-
 // KnownFeatures returns a slice of strings describing the FeatureGate's known features.
 // Deprecated and GA features are hidden from the list.
 func (f *featureGate) KnownFeatures() []string {

server/etcdserver/metrics.go

@@ -140,6 +140,13 @@ var (
 		},
 		[]string{"server_id"},
 	)
+	serverFeatureEnabled = prometheus.NewGaugeVec(
+		prometheus.GaugeOpts{
+			Name: "etcd_server_feature_enabled",
+			Help: "Whether or not a feature is enabled. 1 is enabled, 0 is not.",
+		},
+		[]string{"name", "stage"},
+	)
 	fdUsed = prometheus.NewGauge(prometheus.GaugeOpts{
 		Namespace: "os",
 		Subsystem: "fd",
@@ -170,6 +177,7 @@ func init() {
 	prometheus.MustRegister(currentVersion)
 	prometheus.MustRegister(currentGoVersion)
 	prometheus.MustRegister(serverID)
+	prometheus.MustRegister(serverFeatureEnabled)
 	prometheus.MustRegister(learnerPromoteSucceed)
 	prometheus.MustRegister(learnerPromoteFailed)
 	prometheus.MustRegister(fdUsed)

server/etcdserver/server.go

@@ -342,6 +342,8 @@ func NewServer(cfg config.ServerConfig) (srv *EtcdServer, err error) {
 		firstCommitInTerm:     notify.NewNotifier(),
 		clusterVersionChanged: notify.NewNotifier(),
 	}
+
+	addFeatureGateMetrics(cfg.ServerFeatureGate, serverFeatureEnabled)
 	serverID.With(prometheus.Labels{"server_id": b.cluster.nodeID.String()}).Set(1)
 	srv.cluster.SetVersionChangedNotifier(srv.clusterVersionChanged)
 
@@ -2519,3 +2521,15 @@ func (s *EtcdServer) getTxPostLockInsideApplyHook() func() {
 func (s *EtcdServer) CorruptionChecker() CorruptionChecker {
 	return s.corruptionChecker
 }
+
+func addFeatureGateMetrics(fg featuregate.FeatureGate, guageVec *prometheus.GaugeVec) {
+	for feature, featureSpec := range fg.(featuregate.MutableFeatureGate).GetAll() {
+		var metricVal float64
+		if fg.Enabled(feature) {
+			metricVal = 1
+		} else {
+			metricVal = 0
+		}
+		guageVec.With(prometheus.Labels{"name": string(feature), "stage": string(featureSpec.PreRelease)}).Set(metricVal)
+	}
+}

server/etcdserver/server_test.go

@@ -24,12 +24,15 @@ import (
 	"os"
 	"path/filepath"
 	"reflect"
+	"strings"
 	"sync"
 	"testing"
 	"time"
 
 	"github.com/coreos/go-semver/semver"
 	"github.com/golang/protobuf/proto"
+	"github.com/prometheus/client_golang/prometheus"
+	ptestutil "github.com/prometheus/client_golang/prometheus/testutil"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 	"go.uber.org/zap"
@@ -42,6 +45,7 @@ import (
 	"go.etcd.io/etcd/client/pkg/v3/testutil"
 	"go.etcd.io/etcd/client/pkg/v3/types"
 	"go.etcd.io/etcd/client/pkg/v3/verify"
+	"go.etcd.io/etcd/pkg/v3/featuregate"
 	"go.etcd.io/etcd/pkg/v3/idutil"
 	"go.etcd.io/etcd/pkg/v3/notify"
 	"go.etcd.io/etcd/pkg/v3/pbutil"
@@ -1683,3 +1687,30 @@ func TestIsActive(t *testing.T) {
 		require.Equal(t, tc.expectActive, s.isActive())
 	}
 }
+
+func TestAddFeatureGateMetrics(t *testing.T) {
+	const testAlphaGate featuregate.Feature = "TestAlpha"
+	const testBetaGate featuregate.Feature = "TestBeta"
+	const testGAGate featuregate.Feature = "TestGA"
+
+	featuremap := map[featuregate.Feature]featuregate.FeatureSpec{
+		testGAGate:    {Default: true, PreRelease: featuregate.GA},
+		testAlphaGate: {Default: true, PreRelease: featuregate.Alpha},
+		testBetaGate:  {Default: false, PreRelease: featuregate.Beta},
+	}
+	fg := featuregate.New("test", zaptest.NewLogger(t))
+	fg.Add(featuremap)
+
+	addFeatureGateMetrics(fg, serverFeatureEnabled)
+
+	expected := `# HELP etcd_server_feature_enabled Whether or not a feature is enabled. 1 is enabled, 0 is not.
+	# TYPE etcd_server_feature_enabled gauge
+	etcd_server_feature_enabled{name="AllAlpha",stage="ALPHA"} 0
+	etcd_server_feature_enabled{name="AllBeta",stage="BETA"} 0
+	etcd_server_feature_enabled{name="TestAlpha",stage="ALPHA"} 1
+	etcd_server_feature_enabled{name="TestBeta",stage="BETA"} 0
+	etcd_server_feature_enabled{name="TestGA",stage=""} 1
+	`
+	err := ptestutil.GatherAndCompare(prometheus.DefaultGatherer, strings.NewReader(expected), "etcd_server_feature_enabled")
+	require.NoErrorf(t, err, "unexpected metric collection result: \n%s", err)
+}