Prefer a specific availability zone
Below are examples of setting the "prefer availability zone" balancing algorithm in different YDB SDKs.
package main
import (
"context"
"os"
"github.com/ydb-platform/ydb-go-sdk/v3"
"github.com/ydb-platform/ydb-go-sdk/v3/balancers"
)
func main() {
ctx, cancel := context.WithCancel(context.Background())
defer cancel()
db, err := ydb.Open(ctx,
os.Getenv("YDB_CONNECTION_STRING"),
ydb.WithBalancer(
balancers.PreferLocations(
balancers.RandomChoice(),
"a",
"b",
),
),
)
if err != nil {
panic(err)
}
defer db.Close(ctx)
// ...
}
Client-side balancing in the YDB database/sql driver happens only when opening a new connection (in database/sql terms), which maps to a YDB session on a specific node. After the session is created, all queries on that session go to that node. Queries on the same YDB session are not balanced across nodes.
Example for "prefer availability zone" balancing:
package main
import (
"context"
"database/sql"
"os"
"github.com/ydb-platform/ydb-go-sdk/v3"
"github.com/ydb-platform/ydb-go-sdk/v3/balancers"
)
func main() {
ctx, cancel := context.WithCancel(context.Background())
defer cancel()
nativeDriver, err := ydb.Open(ctx,
os.Getenv("YDB_CONNECTION_STRING"),
ydb.WithBalancer(
balancers.PreferLocations(
balancers.RandomChoice(),
"a",
"b",
),
),
)
if err != nil {
panic(err)
}
defer nativeDriver.Close(ctx)
connector, err := ydb.Connector(nativeDriver)
if err != nil {
panic(err)
}
db := sql.OpenDB(connector)
defer db.Close()
// ...
}
The C++ SDK lets you pick only one availability zone as preferred.
#include <ydb-cpp-sdk/client/driver/driver.h>
int main() {
auto connectionString = std::string(std::getenv("YDB_CONNECTION_STRING"));
auto driverConfig = NYdb::TDriverConfig(connectionString)
.SetBalancingPolicy(NYdb::TBalancingPolicy::UsePreferableLocation("datacenter1"));
NYdb::TDriver driver(driverConfig);
// ...
driver.Stop(true);
return 0;
}
This functionality is not currently supported.
This section is under development.
In the Java SDK, availability zone preference is set on the gRPC transport.
import tech.ydb.core.grpc.BalancingSettings;
import tech.ydb.core.grpc.GrpcTransport;
try (GrpcTransport transport = GrpcTransport.forConnectionString("grpc://localhost:2136/local")
.withBalancingSettings(BalancingSettings.fromLocation("a")) // preferred availability zone
.build()) {
// ...
}
See supported availability-zone parameters in JDBC driver properties, or configure balancing through the native API when embedding the driver.
In Spring Boot, ORMs, and other JDBC wrappers, pass the same JDBC URL and zone parameters as for a direct connection (for example in spring.datasource.url or pool properties).