etcdserver: add "etcd_server_quota_backend_bytes"

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

etcdserver/metrics.go

@@ -71,6 +71,12 @@ var (
 		Name:      "slow_read_indexes_total",
 		Help:      "The total number of pending read indexes not in sync with leader's or timed out read index requests.",
 	})
+	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",
@@ -89,6 +95,7 @@ func init() {
 	prometheus.MustRegister(proposalsPending)
 	prometheus.MustRegister(proposalsFailed)
 	prometheus.MustRegister(slowReadIndex)
+	prometheus.MustRegister(quotaBackendBytes)
 	prometheus.MustRegister(currentVersion)
 
 	currentVersion.With(prometheus.Labels{

etcdserver/quota.go

@@ -50,15 +50,20 @@ const (
 )
 
 func NewBackendQuota(s *EtcdServer) Quota {
+	quotaBackendBytes.Set(float64(s.Cfg.QuotaBackendBytes))
+
 	if s.Cfg.QuotaBackendBytes < 0 {
 		// disable quotas if negative
 		plog.Warningf("disabling backend quota")
 		return &passthroughQuota{}
 	}
+
 	if s.Cfg.QuotaBackendBytes == 0 {
+		quotaBackendBytes.Set(float64(backend.DefaultQuotaBytes))
 		// use default size if no quota size given
 		return &backendQuota{s, backend.DefaultQuotaBytes}
 	}
+
 	if s.Cfg.QuotaBackendBytes > backend.MaxQuotaBytes {
 		plog.Warningf("backend quota %v exceeds maximum quota %v; using maximum", s.Cfg.QuotaBackendBytes, backend.MaxQuotaBytes)
 		return &backendQuota{s, backend.MaxQuotaBytes}