Dynamically register cache provider metrics

main.go

@@ -402,10 +402,10 @@ func main() {
 	}
 
 	if cfg.ProviderCacheTime > 0 {
-		p = &provider.CachedProvider{
-			Provider:     p,
-			RefreshDelay: cfg.ProviderCacheTime,
-		}
+		p = provider.NewCachedProvider(
+			p,
+			cfg.ProviderCacheTime,
+		)
 	}
 
 	var r registry.Registry

provider/cached_provider.go

@@ -17,6 +17,7 @@ package provider
 
 import (
 	"context"
+	"sync"
 	"time"
 
 	"github.com/prometheus/client_golang/prometheus"
@@ -46,6 +47,8 @@ var (
 			Help:      "Number of calls to the provider cache ApplyChanges.",
 		},
 	)
+
+	registerCacheProviderMetrics = sync.Once{}
 )
 
 type CachedProvider struct {
@@ -55,6 +58,16 @@ type CachedProvider struct {
 	cache        []*endpoint.Endpoint
 }
 
+func NewCachedProvider(provider Provider, refreshDelay time.Duration) *CachedProvider {
+	registerMetrics.Do(func() {
+		prometheus.MustRegister(cachedRecordsCallsTotal)
+	})
+	return &CachedProvider{
+		Provider:     provider,
+		RefreshDelay: refreshDelay,
+	}
+}
+
 func (c *CachedProvider) Records(ctx context.Context) ([]*endpoint.Endpoint, error) {
 	if c.needRefresh() {
 		log.Info("Records cache provider: refreshing records list cache")
@@ -95,7 +108,3 @@ func (c *CachedProvider) needRefresh() bool {
 	log.Debug("Records cache last Read: ", c.lastRead, "expiration: ", c.RefreshDelay, " provider expiration:", c.lastRead.Add(c.RefreshDelay), "expired: ", time.Now().After(c.lastRead.Add(c.RefreshDelay)))
 	return time.Now().After(c.lastRead.Add(c.RefreshDelay))
 }
-
-func init() {
-	prometheus.MustRegister(cachedRecordsCallsTotal)
-}