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

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

plugin/metrics/metrics.go

@@ -9,10 +9,10 @@ import (
 	"time"
 
 	"github.com/coredns/coredns/plugin"
-	"github.com/coredns/coredns/plugin/metrics/vars"
 	"github.com/coredns/coredns/plugin/pkg/reuseport"
 
 	"github.com/prometheus/client_golang/prometheus"
+	"github.com/prometheus/client_golang/prometheus/promauto"
 	"github.com/prometheus/client_golang/prometheus/promhttp"
 )
 
@@ -37,23 +37,9 @@ type Metrics struct {
 func New(addr string) *Metrics {
 	met := &Metrics{
 		Addr:    addr,
-		Reg:     prometheus.NewRegistry(),
+		Reg:     prometheus.DefaultRegisterer.(*prometheus.Registry),
 		zoneMap: make(map[string]struct{}),
 	}
-	// Add the default collectors
-	met.MustRegister(prometheus.NewGoCollector())
-	met.MustRegister(prometheus.NewProcessCollector(prometheus.ProcessCollectorOpts{}))
-
-	// Add all of our collectors
-	met.MustRegister(buildInfo)
-	met.MustRegister(vars.Panic)
-	met.MustRegister(vars.RequestCount)
-	met.MustRegister(vars.RequestDuration)
-	met.MustRegister(vars.RequestSize)
-	met.MustRegister(vars.RequestDo)
-	met.MustRegister(vars.ResponseSize)
-	met.MustRegister(vars.ResponseRcode)
-	met.MustRegister(vars.PluginEnabled)
 
 	return met
 }
@@ -162,7 +148,7 @@ var ListenAddr string
 // before erroring when it tries to close the metrics server
 const shutdownTimeout time.Duration = time.Second * 5
 
-var buildInfo = prometheus.NewGaugeVec(prometheus.GaugeOpts{
+var buildInfo = promauto.NewGaugeVec(prometheus.GaugeOpts{
 	Namespace: plugin.Namespace,
 	Name:      "build_info",
 	Help:      "A metric with a constant '1' value labeled by version, revision, and goversion from which CoreDNS was built.",

plugin/metrics/register.go

@@ -1,23 +0,0 @@
-package metrics
-
-import (
-	"github.com/coredns/coredns/core/dnsserver"
-
-	"github.com/caddyserver/caddy"
-	"github.com/prometheus/client_golang/prometheus"
-)
-
-// MustRegister registers the prometheus Collectors when the metrics plugin is used.
-func MustRegister(c *caddy.Controller, cs ...prometheus.Collector) {
-	m := dnsserver.GetConfig(c).Handler("prometheus")
-	if m == nil {
-		return
-	}
-	x, ok := m.(*Metrics)
-	if !ok {
-		return
-	}
-	for _, c := range cs {
-		x.MustRegister(c)
-	}
-}

plugin/metrics/vars/vars.go

@@ -4,18 +4,19 @@ import (
 	"github.com/coredns/coredns/plugin"
 
 	"github.com/prometheus/client_golang/prometheus"
+	"github.com/prometheus/client_golang/prometheus/promauto"
 )
 
 // Request* and Response* are the prometheus counters and gauges we are using for exporting metrics.
 var (
-	RequestCount = prometheus.NewCounterVec(prometheus.CounterOpts{
+	RequestCount = promauto.NewCounterVec(prometheus.CounterOpts{
 		Namespace: plugin.Namespace,
 		Subsystem: subsystem,
 		Name:      "requests_total",
 		Help:      "Counter of DNS requests made per zone, protocol and family.",
 	}, []string{"server", "zone", "proto", "family", "type"})
 
-	RequestDuration = prometheus.NewHistogramVec(prometheus.HistogramOpts{
+	RequestDuration = promauto.NewHistogramVec(prometheus.HistogramOpts{
 		Namespace: plugin.Namespace,
 		Subsystem: subsystem,
 		Name:      "request_duration_seconds",
@@ -23,7 +24,7 @@ var (
 		Help:      "Histogram of the time (in seconds) each request took.",
 	}, []string{"server", "zone", "type"})
 
-	RequestSize = prometheus.NewHistogramVec(prometheus.HistogramOpts{
+	RequestSize = promauto.NewHistogramVec(prometheus.HistogramOpts{
 		Namespace: plugin.Namespace,
 		Subsystem: subsystem,
 		Name:      "request_size_bytes",
@@ -31,14 +32,14 @@ var (
 		Buckets:   []float64{0, 100, 200, 300, 400, 511, 1023, 2047, 4095, 8291, 16e3, 32e3, 48e3, 64e3},
 	}, []string{"server", "zone", "proto"})
 
-	RequestDo = prometheus.NewCounterVec(prometheus.CounterOpts{
+	RequestDo = promauto.NewCounterVec(prometheus.CounterOpts{
 		Namespace: plugin.Namespace,
 		Subsystem: subsystem,
 		Name:      "do_requests_total",
 		Help:      "Counter of DNS requests with DO bit set per zone.",
 	}, []string{"server", "zone"})
 
-	ResponseSize = prometheus.NewHistogramVec(prometheus.HistogramOpts{
+	ResponseSize = promauto.NewHistogramVec(prometheus.HistogramOpts{
 		Namespace: plugin.Namespace,
 		Subsystem: subsystem,
 		Name:      "response_size_bytes",
@@ -46,20 +47,20 @@ var (
 		Buckets:   []float64{0, 100, 200, 300, 400, 511, 1023, 2047, 4095, 8291, 16e3, 32e3, 48e3, 64e3},
 	}, []string{"server", "zone", "proto"})
 
-	ResponseRcode = prometheus.NewCounterVec(prometheus.CounterOpts{
+	ResponseRcode = promauto.NewCounterVec(prometheus.CounterOpts{
 		Namespace: plugin.Namespace,
 		Subsystem: subsystem,
 		Name:      "responses_total",
 		Help:      "Counter of response status codes.",
 	}, []string{"server", "zone", "rcode"})
 
-	Panic = prometheus.NewCounter(prometheus.CounterOpts{
+	Panic = promauto.NewCounter(prometheus.CounterOpts{
 		Namespace: plugin.Namespace,
 		Name:      "panics_total",
 		Help:      "A metrics that counts the number of panics.",
 	})
 
-	PluginEnabled = prometheus.NewGaugeVec(prometheus.GaugeOpts{
+	PluginEnabled = promauto.NewGaugeVec(prometheus.GaugeOpts{
 		Namespace: plugin.Namespace,
 		Name:      "plugin_enabled",
 		Help:      "A metric that indicates whether a plugin is enabled on per server and zone basis.",