diff --git a/pkg/bbgo/environment.go b/pkg/bbgo/environment.go
index c1f8fc22d..4caf86c3d 100644
--- a/pkg/bbgo/environment.go
+++ b/pkg/bbgo/environment.go
@@ -188,8 +188,9 @@ func (environ *Environment) ConfigureDatabase(ctx context.Context, config *Confi
 		dbDriver = "mysql"
 	}
 
-	if dbDriver == "" {
-		return fmt.Errorf("either env DB_DRIVER or config.Driver is not set")
+	// database is optional
+	if dbDriver == "" || dbDSN == "" {
+		return nil
 	}
 
 	return environ.ConfigureDatabaseDriver(ctx, dbDriver, dbDSN, extraPkgNames...)
diff --git a/pkg/indicator/v2/boll.go b/pkg/indicator/v2/boll.go
index 611f0ea34..260d9f4eb 100644
--- a/pkg/indicator/v2/boll.go
+++ b/pkg/indicator/v2/boll.go
@@ -38,7 +38,6 @@ func BOLL(source types.Float64Source, window int, k float64) *BOLLStream {
 		SMA:           sma,
 		StdDev:        stdDev,
 	}
-	s.Bind(source, s)
 
 	// on band update
 	s.Float64Series.OnUpdate(func(band float64) {
@@ -46,6 +45,8 @@ func BOLL(source types.Float64Source, window int, k float64) *BOLLStream {
 		s.UpBand.PushAndEmit(mid + band)
 		s.DownBand.PushAndEmit(mid - band)
 	})
+
+	s.Bind(source, s)
 	return s
 }