etcdserver: add "etcd_server_quota_backend_bytes"

Signed-off-by: Gyuho Lee <gyuhox@gmail.com>

etcdserver/metrics.go

@@ -84,6 +84,12 @@ var (
 		Name:      "lease_expired_total",
 		Help:      "The total number of expired leases.",
 	})
+	quotaBackendBytes = prometheus.NewGauge(prometheus.GaugeOpts{
+		Namespace: "etcd",
+		Subsystem: "server",
+		Name:      "quota_backend_bytes",
+		Help:      "Current backend storage quota size in bytes.",
+	})
 	currentVersion = prometheus.NewGaugeVec(prometheus.GaugeOpts{
 		Namespace: "etcd",
 		Subsystem: "server",
@@ -104,6 +110,7 @@ func init() {
 	prometheus.MustRegister(proposalsPending)
 	prometheus.MustRegister(proposalsFailed)
 	prometheus.MustRegister(leaseExpired)
+	prometheus.MustRegister(quotaBackendBytes)
 	prometheus.MustRegister(currentVersion)
 
 	currentVersion.With(prometheus.Labels{

etcdserver/quota.go

@@ -62,6 +62,7 @@ const (
 
 func NewBackendQuota(s *EtcdServer, name string) Quota {
 	lg := s.getLogger()
+	quotaBackendBytes.Set(float64(s.Cfg.QuotaBackendBytes))
 
 	if s.Cfg.QuotaBackendBytes < 0 {
 		// disable quotas if negative
@@ -87,6 +88,7 @@ func NewBackendQuota(s *EtcdServer, name string) Quota {
 				zap.String("quota-size", humanize.Bytes(uint64(DefaultQuotaBytes))),
 			)
 		}
+		quotaBackendBytes.Set(float64(DefaultQuotaBytes))
 		return &backendQuota{s, DefaultQuotaBytes}
 	}