Register Prometheus etcdmetrics only for apiserver

Removed automatic registration with `init` funciton and use `Register` function
to register metrics for etcd storage only when requested.

staging/src/k8s.io/apiserver/pkg/endpoints/metrics/metrics.go

@@ -18,12 +18,12 @@ package metrics
 
 import (
 	"bufio"
-	//"fmt"
 	"net"
 	"net/http"
 	"regexp"
 	"strconv"
 	"strings"
+	"sync"
 	"time"
 
 	utilnet "k8s.io/apimachinery/pkg/util/net"
@@ -33,6 +33,13 @@ import (
 	"github.com/prometheus/client_golang/prometheus"
 )
 
+// resettableCollector is the interface implemented by prometheus.MetricVec
+// that can be used by Prometheus to collect metrics and reset their values.
+type resettableCollector interface {
+	prometheus.Collector
+	Reset()
+}
+
 var (
 	// TODO(a-robinson): Add unit tests for the handling of these metrics once
 	// the upstream library supports it.
@@ -96,6 +103,16 @@ var (
 		[]string{"requestKind"},
 	)
 	kubectlExeRegexp = regexp.MustCompile(`^.*((?i:kubectl\.exe))`)
+
+	metrics = []resettableCollector{
+		requestCounter,
+		longRunningRequestGauge,
+		requestLatencies,
+		requestLatenciesSummary,
+		responseSizes,
+		DroppedRequests,
+		currentInflightRequests,
+	}
 )
 
 const (
@@ -105,15 +122,22 @@ const (
 	MutatingKind = "mutating"
 )
 
-func init() {
+var registerMetrics sync.Once
-	// Register all metrics.
+
-	prometheus.MustRegister(requestCounter)
+// Register all metrics.
-	prometheus.MustRegister(longRunningRequestGauge)
+func Register() {
-	prometheus.MustRegister(requestLatencies)
+	registerMetrics.Do(func() {
-	prometheus.MustRegister(requestLatenciesSummary)
+		for _, metric := range metrics {
-	prometheus.MustRegister(responseSizes)
+			prometheus.MustRegister(metric)
-	prometheus.MustRegister(DroppedRequests)
+		}
-	prometheus.MustRegister(currentInflightRequests)
+	})
+}
+
+// Reset all metrics.
+func Reset() {
+	for _, metric := range metrics {
+		metric.Reset()
+	}
 }
 
 func UpdateInflightRequestMetrics(nonmutating, mutating int) {
@@ -170,13 +194,6 @@ func MonitorRequest(req *http.Request, verb, resource, subresource, scope, conte
 	}
 }
 
-func Reset() {
-	requestCounter.Reset()
-	requestLatencies.Reset()
-	requestLatenciesSummary.Reset()
-	responseSizes.Reset()
-}
-
 // InstrumentRouteFunc works like Prometheus' InstrumentHandlerFunc but wraps
 // the go-restful RouteFunction instead of a HandlerFunc plus some Kubernetes endpoint specific information.
 func InstrumentRouteFunc(verb, resource, subresource, scope string, routeFunc restful.RouteFunction) restful.RouteFunction {

staging/src/k8s.io/apiserver/pkg/server/routes/metrics.go

@@ -32,6 +32,7 @@ type DefaultMetrics struct{}
 
 // Install adds the DefaultMetrics handler
 func (m DefaultMetrics) Install(c *mux.PathRecorderMux) {
+	register()
 	c.Handle("/metrics", prometheus.Handler())
 }
 
@@ -41,6 +42,7 @@ type MetricsWithReset struct{}
 
 // Install adds the MetricsWithReset handler
 func (m MetricsWithReset) Install(c *mux.PathRecorderMux) {
+	register()
 	defaultMetricsHandler := prometheus.Handler().ServeHTTP
 	c.HandleFunc("/metrics", func(w http.ResponseWriter, req *http.Request) {
 		if req.Method == "DELETE" {
@@ -52,3 +54,9 @@ func (m MetricsWithReset) Install(c *mux.PathRecorderMux) {
 		defaultMetricsHandler(w, req)
 	})
 }
+
+// register apiserver and etcd metrics
+func register() {
+	apimetrics.Register()
+	etcdmetrics.Register()
+}

staging/src/k8s.io/apiserver/pkg/storage/etcd/etcd_helper.go

@@ -101,10 +101,6 @@ type etcdHelper struct {
 	cache utilcache.Cache
 }
 
-func init() {
-	metrics.Register()
-}
-
 // Implements storage.Interface.
 func (h *etcdHelper) Versioner() storage.Versioner {
 	return h.versioner