diff --git a/cmd/opera/launcher/metrics/metrics.go b/cmd/opera/launcher/metrics/metrics.go
index 6249b4954..bab964d68 100644
--- a/cmd/opera/launcher/metrics/metrics.go
+++ b/cmd/opera/launcher/metrics/metrics.go
@@ -3,28 +3,46 @@ package metrics
 import (
 	"os"
 	"path/filepath"
+	"sync"
 	"sync/atomic"
+	"time"
 
 	"github.com/ethereum/go-ethereum/log"
 	"github.com/ethereum/go-ethereum/metrics"
 )
 
-var (
-	// TODO: refactor it
-	dbDir        atomic.Value
-	dbSizeMetric = metrics.NewRegisteredFunctionalGauge("db_size", nil, measureDbDir)
-)
+var once sync.Once
 
 func SetDataDir(datadir string) {
-	dbDir.Store(datadir)
+	once.Do(func() {
+		go measureDbDir("db_size", datadir)
+	})
 }
 
-func measureDbDir() (size int64) {
-	datadir, ok := dbDir.Load().(string)
-	if !ok || datadir == "" || datadir == "inmemory" {
-		return
+func measureDbDir(name, datadir string) {
+	var (
+		dbSize  atomic.Int64
+		gauge   metrics.Gauge
+		rescan = (len(datadir) > 0 && datadir != "inmemory")
+	)
+	for {
+		time.Sleep(time.Second)
+
+		if rescan {
+			size := sizeOfDir(datadir)
+			dbSize.Store(size)
+		}
+
+		if gauge == nil {
+			gauge = metrics.NewRegisteredFunctionalGauge(name, nil, func() int64 {
+				return dbSize.Load()
+			})
+		}
+
+		if !rescan {
+			break
+		}
 	}
-	return sizeOfDir(datadir)
 }
 
 func sizeOfDir(dir string) (size int64) {
diff --git a/demo/start.sh b/demo/start.sh
index 5ecc72bcc..763c6a529 100755
--- a/demo/start.sh
+++ b/demo/start.sh
@@ -25,6 +25,7 @@ do
 	--nat extip:127.0.0.1 \
 	--http --http.addr="127.0.0.1" --http.port=${RPCP} --http.corsdomain="*" --http.api="eth,debug,net,admin,web3,personal,txpool,ftm,dag" \
 	--ws --ws.addr="127.0.0.1" --ws.port=${WSP} --ws.origins="*" --ws.api="eth,debug,net,admin,web3,personal,txpool,ftm,dag" \
+	--metrics --metrics.addr=127.0.0.1 --metrics.port=$(($RPCP+1100)) \
 	--verbosity=3 --tracing >> opera$i.log 2>&1)&
 
     echo -e "\tnode$i ok"