using promauto package to ensure all created metrics are properly registered (#4025)

Signed-off-by: zounengren <zounengren@cmss.chinamobile.com>

plugin/reload/metrics.go

@@ -4,19 +4,20 @@ import (
 	"github.com/coredns/coredns/plugin"
 
 	"github.com/prometheus/client_golang/prometheus"
+	"github.com/prometheus/client_golang/prometheus/promauto"
 )
 
 // Metrics for the reload plugin
 var (
 	// failedCount is the counter of the number of failed reload attempts.
-	failedCount = prometheus.NewCounter(prometheus.CounterOpts{
+	failedCount = promauto.NewCounter(prometheus.CounterOpts{
 		Namespace: plugin.Namespace,
 		Subsystem: "reload",
 		Name:      "failed_total",
 		Help:      "Counter of the number of failed reload attempts.",
 	})
 	// reloadInfo is record the hash value during reload.
-	reloadInfo = prometheus.NewGaugeVec(prometheus.GaugeOpts{
+	reloadInfo = promauto.NewGaugeVec(prometheus.GaugeOpts{
 		Namespace: plugin.Namespace,
 		Subsystem: "reload",
 		Name:      "version_info",

plugin/reload/setup.go

@@ -7,7 +7,6 @@ import (
 	"time"
 
 	"github.com/coredns/coredns/plugin"
-	"github.com/coredns/coredns/plugin/metrics"
 	clog "github.com/coredns/coredns/plugin/pkg/log"
 
 	"github.com/caddyserver/caddy"
@@ -70,10 +69,6 @@ func setup(c *caddy.Controller) error {
 	r.setUsage(used)
 	once.Do(func() {
 		caddy.RegisterEventHook("reload", hook)
-		c.OnRestart(func() error {
-			metrics.MustRegister(c, reloadInfo, failedCount)
-			return nil
-		})
 	})
 	// re-register on finalShutDown as the instance most-likely will be changed
 	shutOnce.Do(func() {