---
metadata:
  - name: generator
    content: Diplodoc Platform v5.52.0
alternate:
  - https://ydb.tech/docs/en/recipes/ydb-sdk/balancing-random-choice.md?version=v25.3
  - https://ydb.tech/docs/ru/recipes/ydb-sdk/balancing-random-choice.md?version=v25.3
  - href: en/recipes/ydb-sdk/balancing-random-choice.md
    type: text/markdown
    title: Markdown version
  - href: ../../llms.txt
    type: text/markdown
    title: llms.txt
sourcePath: en/core/recipes/ydb-sdk/balancing-random-choice.md
---
> **Documentation Index:** Fetch the complete configuration index at https://ydb.tech/docs/en/llms.txt

# Random choice

The YDB SDK uses the `random_choice` (uniform random) balancing algorithm by default, except the C++ SDK, which defaults to ["prefer the nearest data center"](https://ydb.tech/docs/en/recipes/ydb-sdk/balancing-prefer-local.md?version=v25.3).

Below are examples of explicitly setting the "random choice" balancing algorithm in different YDB SDKs.

{% list tabs %}

- Go

  {% list tabs %}

  - Native SDK

    ```go
    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.RandomChoice(),
        ),
      )
      if err != nil {
        panic(err)
      }
      defer db.Close(ctx)
      // ...
    }
    ```

  - database/sql

    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 "random choice" balancing:

    ```go
    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.RandomChoice(),
        ),
      )
      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()
      // ...
    }
    ```

  {% endlist %}

- C++

  ```cpp
  #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::UseAllNodes());

    NYdb::TDriver driver(driverConfig);
    // ...
    driver.Stop(true);
    return 0;
  }
  ```

- Python

  {% list tabs %}

  - Native SDK

    ```python
    import os
    import ydb

    driver_config = ydb.DriverConfig(
        endpoint=os.environ["YDB_ENDPOINT"],
        database=os.environ["YDB_DATABASE"],
        credentials=ydb.credentials_from_env_variables(),
        use_all_nodes=True,  # uniform random choice
    )

    with ydb.Driver(driver_config) as driver:
        driver.wait(timeout=5)
        # ...
    ```

  - Native SDK (Asyncio)

    ```python
    import os
    import ydb
    import asyncio

    async def ydb_init():
        driver_config = ydb.DriverConfig(
            endpoint=os.environ["YDB_ENDPOINT"],
            database=os.environ["YDB_DATABASE"],
            credentials=ydb.credentials_from_env_variables(),
            use_all_nodes=True,  # uniform random choice
        )
        async with ydb.aio.Driver(driver_config) as driver:
            await driver.wait()
            # ...

    asyncio.run(ydb_init())
    ```

  - SQLAlchemy

    ```python
    import os
    import sqlalchemy as sa

    engine = sa.create_engine(
        os.environ["YDB_SQLALCHEMY_URL"],
        connect_args={
            "driver_config_kwargs": {
                "use_all_nodes": True,  # uniform random choice
            }
        },
    )
    ```

  {% endlist %}

{% endlist %}