discoveryserver: use custom metrics registry

Use a custom metrics registry so this program doesn't pickup all of the
random guages registered via init functions in the rest of etcd.

discoveryserver/handlers/health.go

@@ -21,7 +21,9 @@ import (
 	"net/http"
 
 	"github.com/prometheus/client_golang/prometheus"
+
 	"go.etcd.io/etcd/discoveryserver/handlers/httperror"
+	"go.etcd.io/etcd/discoveryserver/metrics"
 )
 
 var healthCounter *prometheus.CounterVec
@@ -34,7 +36,7 @@ func init() {
 		},
 		[]string{"code", "method"},
 	)
-	prometheus.MustRegister(healthCounter)
+	metrics.Registry.MustRegister(healthCounter)
 }
 
 func HealthHandler(ctx context.Context, w http.ResponseWriter, r *http.Request) {

discoveryserver/handlers/new.go

@@ -31,6 +31,7 @@ import (
 
 	"go.etcd.io/etcd/clientv3"
 	"go.etcd.io/etcd/discoveryserver/handlers/httperror"
+	"go.etcd.io/etcd/discoveryserver/metrics"
 	"go.etcd.io/etcd/discoveryserver/timeprefix"
 	"go.etcd.io/etcd/etcdserver/api/v2store"
 	"go.etcd.io/etcd/etcdserver/api/v2v3"
@@ -49,7 +50,7 @@ func init() {
 		},
 		[]string{"code", "method"},
 	)
-	prometheus.MustRegister(newCounter)
+	metrics.Registry.MustRegister(newCounter)
 }
 
 func generateCluster() string {

discoveryserver/handlers/token.go

@@ -26,6 +26,7 @@ import (
 	"time"
 
 	"go.etcd.io/etcd/discoveryserver/handlers/httperror"
+	"go.etcd.io/etcd/discoveryserver/metrics"
 	"go.etcd.io/etcd/etcdserver/api/v2store"
 
 	"github.com/prometheus/client_golang/prometheus"
@@ -39,7 +40,7 @@ func init() {
 		},
 		[]string{"code", "method"},
 	)
-	prometheus.MustRegister(tokenCounter)
+	metrics.Registry.MustRegister(tokenCounter)
 }
 
 var tokenCounter *prometheus.CounterVec
@@ -127,6 +128,7 @@ func TokenHandler(ctx context.Context, w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
+	tokenCounter.WithLabelValues("200", r.Method).Add(1)
 	w.Header().Set("Content-Type", "application/json")
 	w.Header().Set("X-Etcd-Index", fmt.Sprintf("%d", ev.EtcdIndex))
 	w.WriteHeader(http.StatusOK)

discoveryserver/http/http.go

@@ -20,6 +20,7 @@ import (
 	"os"
 
 	"go.etcd.io/etcd/discoveryserver/handlers"
+	"go.etcd.io/etcd/discoveryserver/metrics"
 
 	gorillaHandlers "github.com/gorilla/handlers"
 	"github.com/gorilla/mux"
@@ -31,7 +32,7 @@ func Setup(ctx context.Context, etcdHost, discHost string) *handlers.State {
 	logH := gorillaHandlers.LoggingHandler(os.Stdout, handler)
 
 	http.Handle("/", logH)
-	http.Handle("/metrics", promhttp.Handler())
+	http.Handle("/metrics", promhttp.HandlerFor(metrics.Registry, promhttp.HandlerOpts{}))
 
 	return st
 }

discoveryserver/metrics/metrics.go

@@ -0,0 +1,23 @@
+// Copyright 2019 The etcd 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 "github.com/prometheus/client_golang/prometheus"
+
+var Registry *prometheus.Registry
+
+func init() {
+	Registry = prometheus.NewRegistry()
+}