allow to use common balancer in child drivers

CHANGELOG.md

@@ -1,3 +1,5 @@
+* Use common balancer for child drivers
+
 ## v3.89.0
 * Fixed send optional arguments to the server with `ydb.ParamsBuilder`
 

driver.go

@@ -415,8 +415,9 @@ func (d *Driver) connect(ctx context.Context) (err error) {
 	if d.pool == nil {
 		d.pool = conn.NewPool(ctx, d.config)
 	}
-
-	d.balancer, err = balancer.New(ctx, d.config, d.pool, d.discoveryOptions...)
+	if d.balancer == nil {
+		d.balancer, err = balancer.New(ctx, d.config, d.pool, d.discoveryOptions...)
+	}
 	if err != nil {
 		return xerrors.WithStackTrace(err)
 	}

options.go

@@ -11,6 +11,7 @@
 
 	"github.com/ydb-platform/ydb-go-sdk/v3/config"
 	"github.com/ydb-platform/ydb-go-sdk/v3/credentials"
+	"github.com/ydb-platform/ydb-go-sdk/v3/internal/balancer"
 	balancerConfig "github.com/ydb-platform/ydb-go-sdk/v3/internal/balancer/config"
 	"github.com/ydb-platform/ydb-go-sdk/v3/internal/certificates"
 	"github.com/ydb-platform/ydb-go-sdk/v3/internal/conn"
@@ -804,3 +805,11 @@
 		return pool.Take(ctx)
 	}
 }
+
+func WithSharedBalancer(parent *Driver) Option {
+	return func(ctx context.Context, c *Driver) error {
+		c.balancer = parent.balancer
+
+		return nil
+	}
+}

with.go

@@ -19,16 +19,14 @@ func (d *Driver) with(ctx context.Context, opts ...Option) (*Driver, uint64, err
 		append(
 			append(
 				d.opts,
-				WithBalancer(
-					d.config.Balancer(),
-				),
 				withOnClose(func(child *Driver) {
 					d.childrenMtx.Lock()
 					defer d.childrenMtx.Unlock()
 
 					delete(d.children, id)
 				}),
 				withConnPool(d.pool),
+				WithSharedBalancer(d),
 			),
 			opts...,
 		)...,