Use CreateDBInstance with an Amazon SDK or command line tool

    /// <summary>
    /// Create an Amazon Relational Database Service (Amazon RDS) DB instance
    /// with a particular set of properties. Use the action DescribeDBInstancesAsync
    /// to determine when the DB instance is ready to use.
    /// </summary>
    /// <param name="dbInstanceIdentifier">DB instance identifier.</param>
    /// <param name="dbClusterIdentifier">DB cluster identifier.</param>
    /// <param name="dbEngine">The engine for the DB instance.</param>
    /// <param name="dbEngineVersion">Version for the DB instance.</param>
    /// <param name="instanceClass">Class for the DB instance.</param>
    /// <returns>DB instance object.</returns>
    public async Task<DBInstance> CreateDBInstanceInClusterAsync(
        string dbClusterIdentifier,
        string dbInstanceIdentifier,
        string dbEngine,
        string dbEngineVersion,
        string instanceClass)
    {
        // When creating the instance within a cluster, do not specify the name or size.
        var response = await _amazonRDS.CreateDBInstanceAsync(
            new CreateDBInstanceRequest()
            {
                DBClusterIdentifier = dbClusterIdentifier,
                DBInstanceIdentifier = dbInstanceIdentifier,
                Engine = dbEngine,
                EngineVersion = dbEngineVersion,
                DBInstanceClass = instanceClass
            });

        return response.DBInstance;
    }

        Aws::Client::ClientConfiguration clientConfig;
        // Optional: Set to the AWS Region (overrides config file).
        // clientConfig.region = "us-east-1";

    Aws::RDS::RDSClient client(clientConfig);

        Aws::RDS::Model::CreateDBInstanceRequest request;
        request.SetDBInstanceIdentifier(DB_INSTANCE_IDENTIFIER);
        request.SetDBClusterIdentifier(DB_CLUSTER_IDENTIFIER);
        request.SetEngine(engineName);
        request.SetDBInstanceClass(dbInstanceClass);

        Aws::RDS::Model::CreateDBInstanceOutcome outcome =
                client.CreateDBInstance(request);

        if (outcome.IsSuccess()) {
            std::cout << "The DB instance creation has started."
                      << std::endl;
        }
        else {
            std::cerr << "Error with RDS::CreateDBInstance. "
                      << outcome.GetError().GetMessage()
                      << std::endl;
            cleanUpResources(CLUSTER_PARAMETER_GROUP_NAME, DB_CLUSTER_IDENTIFIER, "",
                             client);
            return false;
        }

type DbClusters struct {
	AuroraClient *rds.Client
}



// CreateInstanceInCluster creates a database instance in an existing DB cluster. The first database that is
// created defaults to a read-write DB instance.
func (clusters *DbClusters) CreateInstanceInCluster(clusterName string, instanceName string,
	dbEngine string, dbInstanceClass string) (*types.DBInstance, error) {
	output, err := clusters.AuroraClient.CreateDBInstance(context.TODO(), &rds.CreateDBInstanceInput{
		DBInstanceIdentifier: aws.String(instanceName),
		DBClusterIdentifier:  aws.String(clusterName),
		Engine:               aws.String(dbEngine),
		DBInstanceClass:      aws.String(dbInstanceClass),
	})
	if err != nil {
		log.Printf("Couldn't create instance %v: %v\n", instanceName, err)
		return nil, err
	} else {
		return output.DBInstance, nil
	}
}

    public static String createDBInstanceCluster(RdsClient rdsClient,
            String dbInstanceIdentifier,
            String dbInstanceClusterIdentifier,
            String instanceClass) {
        try {
            CreateDbInstanceRequest instanceRequest = CreateDbInstanceRequest.builder()
                    .dbInstanceIdentifier(dbInstanceIdentifier)
                    .dbClusterIdentifier(dbInstanceClusterIdentifier)
                    .engine("aurora-mysql")
                    .dbInstanceClass(instanceClass)
                    .build();

            CreateDbInstanceResponse response = rdsClient.createDBInstance(instanceRequest);
            System.out.print("The status is " + response.dbInstance().dbInstanceStatus());
            return response.dbInstance().dbInstanceArn();

        } catch (RdsException e) {
            System.err.println(e.getMessage());
            System.exit(1);
        }
        return "";
    }

suspend fun createDBInstanceCluster(dbInstanceIdentifierVal: String?, dbInstanceClusterIdentifierVal: String?, instanceClassVal: String?): String? {
    val instanceRequest = CreateDbInstanceRequest {
        dbInstanceIdentifier = dbInstanceIdentifierVal
        dbClusterIdentifier = dbInstanceClusterIdentifierVal
        engine = "aurora-mysql"
        dbInstanceClass = instanceClassVal
    }

    RdsClient { region = "us-west-2" }.use { rdsClient ->
        val response = rdsClient.createDbInstance(instanceRequest)
        print("The status is ${response.dbInstance?.dbInstanceStatus}")
        return response.dbInstance?.dbInstanceArn
    }
}

class AuroraWrapper:
    """Encapsulates Aurora DB cluster actions."""

    def __init__(self, rds_client):
        """
        :param rds_client: A Boto3 Amazon Relational Database Service (Amazon RDS) client.
        """
        self.rds_client = rds_client

    @classmethod
    def from_client(cls):
        """
        Instantiates this class from a Boto3 client.
        """
        rds_client = boto3.client("rds")
        return cls(rds_client)


    def create_instance_in_cluster(
        self, instance_id, cluster_id, db_engine, instance_class
    ):
        """
        Creates a database instance in an existing DB cluster. The first database that is
        created defaults to a read-write DB instance.

        :param instance_id: The ID to give the newly created DB instance.
        :param cluster_id: The ID of the DB cluster where the DB instance is created.
        :param db_engine: The database engine of a database to create in the DB instance.
                          This must be compatible with the configured parameter group
                          of the DB cluster.
        :param instance_class: The DB instance class for the newly created DB instance.
        :return: Data about the newly created DB instance.
        """
        try:
            response = self.rds_client.create_db_instance(
                DBInstanceIdentifier=instance_id,
                DBClusterIdentifier=cluster_id,
                Engine=db_engine,
                DBInstanceClass=instance_class,
            )
            db_inst = response["DBInstance"]
        except ClientError as err:
            logger.error(
                "Couldn't create DB instance %s. Here's why: %s: %s",
                instance_id,
                err.response["Error"]["Code"],
                err.response["Error"]["Message"],
            )
            raise
        else:
            return db_inst

    // Get a list of allowed engine versions. rds.DescribeDbEngineVersions(Engine='aurora-mysql', DBParameterGroupFamily=<the family used to create your parameter group in step 2>)
    // Create an Aurora DB cluster database cluster that contains a MySql database and uses the parameter group you created.
    // Wait for DB cluster to be ready. Call rds.DescribeDBClusters and check for Status == 'available'.
    // Get a list of instance classes available for the selected engine and engine version. rds.DescribeOrderableDbInstanceOptions(Engine='mysql', EngineVersion=).

    // Create a database instance in the cluster.
    // Wait for DB instance to be ready. Call rds.DescribeDbInstances and check for DBInstanceStatus == 'available'.
    pub async fn start_cluster_and_instance(&mut self) -> Result<(), ScenarioError> {
        if self.password.is_none() {
            return Err(ScenarioError::with(
                "Must set Secret Password before starting a cluster",
            ));
        }
        let create_db_cluster = self
            .rds
            .create_db_cluster(
                DB_CLUSTER_IDENTIFIER,
                DB_CLUSTER_PARAMETER_GROUP_NAME,
                DB_ENGINE,
                self.engine_version.as_deref().expect("engine version"),
                self.username.as_deref().expect("username"),
                self.password
                    .replace(SecretString::new("".to_string()))
                    .expect("password"),
            )
            .await;
        if let Err(err) = create_db_cluster {
            return Err(ScenarioError::new(
                "Failed to create DB Cluster with cluster group",
                &err,
            ));
        }

        self.db_cluster_identifier = create_db_cluster
            .unwrap()
            .db_cluster
            .and_then(|c| c.db_cluster_identifier);

        if self.db_cluster_identifier.is_none() {
            return Err(ScenarioError::with("Created DB Cluster missing Identifier"));
        }

        info!(
            "Started a db cluster: {}",
            self.db_cluster_identifier
                .as_deref()
                .unwrap_or("Missing ARN")
        );

        let create_db_instance = self
            .rds
            .create_db_instance(
                self.db_cluster_identifier.as_deref().expect("cluster name"),
                DB_INSTANCE_IDENTIFIER,
                self.instance_class.as_deref().expect("instance class"),
                DB_ENGINE,
            )
            .await;
        if let Err(err) = create_db_instance {
            return Err(ScenarioError::new(
                "Failed to create Instance in DB Cluster",
                &err,
            ));
        }

        self.db_instance_identifier = create_db_instance
            .unwrap()
            .db_instance
            .and_then(|i| i.db_instance_identifier);

        // Cluster creation can take up to 20 minutes to become available
        let cluster_max_wait = Duration::from_secs(20 * 60);
        let waiter = Waiter::builder().max(cluster_max_wait).build();
        while waiter.sleep().await.is_ok() {
            let cluster = self
                .rds
                .describe_db_clusters(
                    self.db_cluster_identifier
                        .as_deref()
                        .expect("cluster identifier"),
                )
                .await;

            if let Err(err) = cluster {
                warn!(?err, "Failed to describe cluster while waiting for ready");
                continue;
            }

            let instance = self
                .rds
                .describe_db_instance(
                    self.db_instance_identifier
                        .as_deref()
                        .expect("instance identifier"),
                )
                .await;
            if let Err(err) = instance {
                return Err(ScenarioError::new(
                    "Failed to find instance for cluster",
                    &err,
                ));
            }

            let instances_available = instance
                .unwrap()
                .db_instances()
                .iter()
                .all(|instance| instance.db_instance_status() == Some("Available"));

            let endpoints = self
                .rds
                .describe_db_cluster_endpoints(
                    self.db_cluster_identifier
                        .as_deref()
                        .expect("cluster identifier"),
                )
                .await;

            if let Err(err) = endpoints {
                return Err(ScenarioError::new(
                    "Failed to find endpoint for cluster",
                    &err,
                ));
            }

            let endpoints_available = endpoints
                .unwrap()
                .db_cluster_endpoints()
                .iter()
                .all(|endpoint| endpoint.status() == Some("available"));

            if instances_available && endpoints_available {
                return Ok(());
            }
        }

        Err(ScenarioError::with("timed out waiting for cluster"))
    }

    pub async fn create_db_instance(
        &self,
        cluster_name: &str,
        instance_name: &str,
        instance_class: &str,
        engine: &str,
    ) -> Result<CreateDbInstanceOutput, SdkError<CreateDBInstanceError>> {
        self.inner
            .create_db_instance()
            .db_cluster_identifier(cluster_name)
            .db_instance_identifier(instance_name)
            .db_instance_class(instance_class)
            .engine(engine)
            .send()
            .await
    }

#[tokio::test]
async fn test_start_cluster_and_instance() {
    let mut mock_rds = MockRdsImpl::default();

    mock_rds
        .expect_create_db_cluster()
        .withf(|id, params, engine, version, username, password| {
            assert_eq!(id, "RustSDKCodeExamplesDBCluster");
            assert_eq!(params, "RustSDKCodeExamplesDBParameterGroup");
            assert_eq!(engine, "aurora-mysql");
            assert_eq!(version, "aurora-mysql8.0");
            assert_eq!(username, "test username");
            assert_eq!(password.expose_secret(), "test password");
            true
        })
        .return_once(|id, _, _, _, _, _| {
            Ok(CreateDbClusterOutput::builder()
                .db_cluster(DbCluster::builder().db_cluster_identifier(id).build())
                .build())
        });

    mock_rds
        .expect_create_db_instance()
        .withf(|cluster, name, class, engine| {
            assert_eq!(cluster, "RustSDKCodeExamplesDBCluster");
            assert_eq!(name, "RustSDKCodeExamplesDBInstance");
            assert_eq!(class, "m5.large");
            assert_eq!(engine, "aurora-mysql");
            true
        })
        .return_once(|cluster, name, class, _| {
            Ok(CreateDbInstanceOutput::builder()
                .db_instance(
                    DbInstance::builder()
                        .db_cluster_identifier(cluster)
                        .db_instance_identifier(name)
                        .db_instance_class(class)
                        .build(),
                )
                .build())
        });

    mock_rds
        .expect_describe_db_clusters()
        .with(eq("RustSDKCodeExamplesDBCluster"))
        .return_once(|id| {
            Ok(DescribeDbClustersOutput::builder()
                .db_clusters(DbCluster::builder().db_cluster_identifier(id).build())
                .build())
        });

    mock_rds
        .expect_describe_db_instance()
        .with(eq("RustSDKCodeExamplesDBInstance"))
        .return_once(|name| {
            Ok(DescribeDbInstancesOutput::builder()
                .db_instances(
                    DbInstance::builder()
                        .db_instance_identifier(name)
                        .db_instance_status("Available")
                        .build(),
                )
                .build())
        });

    mock_rds
        .expect_describe_db_cluster_endpoints()
        .with(eq("RustSDKCodeExamplesDBCluster"))
        .return_once(|_| {
            Ok(DescribeDbClusterEndpointsOutput::builder()
                .db_cluster_endpoints(DbClusterEndpoint::builder().status("available").build())
                .build())
        });

    let mut scenario = AuroraScenario::new(mock_rds);
    scenario.engine_version = Some("aurora-mysql8.0".into());
    scenario.instance_class = Some("m5.large".into());
    scenario.username = Some("test username".into());
    scenario.password = Some(SecretString::new("test password".into()));

    tokio::time::pause();
    let assertions = tokio::spawn(async move {
        let create = scenario.start_cluster_and_instance().await;
        assert!(create.is_ok());
        assert!(scenario
            .password
            .replace(SecretString::new("BAD SECRET".into()))
            .unwrap()
            .expose_secret()
            .is_empty());
        assert_eq!(
            scenario.db_cluster_identifier,
            Some("RustSDKCodeExamplesDBCluster".into())
        );
    });
    tokio::time::advance(Duration::from_secs(1)).await;
    tokio::time::resume();
    let _ = assertions.await;
}

#[tokio::test]
async fn test_start_cluster_and_instance_cluster_create_error() {
    let mut mock_rds = MockRdsImpl::default();

    mock_rds
        .expect_create_db_cluster()
        .return_once(|_, _, _, _, _, _| {
            Err(SdkError::service_error(
                CreateDBClusterError::unhandled(Box::new(Error::new(
                    ErrorKind::Other,
                    "create db cluster error",
                ))),
                Response::new(StatusCode::try_from(400).unwrap(), SdkBody::empty()),
            ))
        });

    let mut scenario = AuroraScenario::new(mock_rds);
    scenario.engine_version = Some("aurora-mysql8.0".into());
    scenario.instance_class = Some("m5.large".into());
    scenario.username = Some("test username".into());
    scenario.password = Some(SecretString::new("test password".into()));

    let create = scenario.start_cluster_and_instance().await;
    assert_matches!(create, Err(ScenarioError { message, context: _}) if message == "Failed to create DB Cluster with cluster group")
}

#[tokio::test]
async fn test_start_cluster_and_instance_cluster_create_missing_id() {
    let mut mock_rds = MockRdsImpl::default();

    mock_rds
        .expect_create_db_cluster()
        .return_once(|_, _, _, _, _, _| {
            Ok(CreateDbClusterOutput::builder()
                .db_cluster(DbCluster::builder().build())
                .build())
        });

    let mut scenario = AuroraScenario::new(mock_rds);
    scenario.engine_version = Some("aurora-mysql8.0".into());
    scenario.instance_class = Some("m5.large".into());
    scenario.username = Some("test username".into());
    scenario.password = Some(SecretString::new("test password".into()));

    let create = scenario.start_cluster_and_instance().await;
    assert_matches!(create, Err(ScenarioError { message, context:_ }) if message == "Created DB Cluster missing Identifier");
}

#[tokio::test]
async fn test_start_cluster_and_instance_instance_create_error() {
    let mut mock_rds = MockRdsImpl::default();

    mock_rds
        .expect_create_db_cluster()
        .withf(|id, params, engine, version, username, password| {
            assert_eq!(id, "RustSDKCodeExamplesDBCluster");
            assert_eq!(params, "RustSDKCodeExamplesDBParameterGroup");
            assert_eq!(engine, "aurora-mysql");
            assert_eq!(version, "aurora-mysql8.0");
            assert_eq!(username, "test username");
            assert_eq!(password.expose_secret(), "test password");
            true
        })
        .return_once(|id, _, _, _, _, _| {
            Ok(CreateDbClusterOutput::builder()
                .db_cluster(DbCluster::builder().db_cluster_identifier(id).build())
                .build())
        });

    mock_rds
        .expect_create_db_instance()
        .return_once(|_, _, _, _| {
            Err(SdkError::service_error(
                CreateDBInstanceError::unhandled(Box::new(Error::new(
                    ErrorKind::Other,
                    "create db instance error",
                ))),
                Response::new(StatusCode::try_from(400).unwrap(), SdkBody::empty()),
            ))
        });

    let mut scenario = AuroraScenario::new(mock_rds);
    scenario.engine_version = Some("aurora-mysql8.0".into());
    scenario.instance_class = Some("m5.large".into());
    scenario.username = Some("test username".into());
    scenario.password = Some(SecretString::new("test password".into()));

    let create = scenario.start_cluster_and_instance().await;
    assert_matches!(create, Err(ScenarioError { message, context: _ }) if message == "Failed to create Instance in DB Cluster")
}

#[tokio::test]
async fn test_start_cluster_and_instance_wait_hiccup() {
    let mut mock_rds = MockRdsImpl::default();

    mock_rds
        .expect_create_db_cluster()
        .withf(|id, params, engine, version, username, password| {
            assert_eq!(id, "RustSDKCodeExamplesDBCluster");
            assert_eq!(params, "RustSDKCodeExamplesDBParameterGroup");
            assert_eq!(engine, "aurora-mysql");
            assert_eq!(version, "aurora-mysql8.0");
            assert_eq!(username, "test username");
            assert_eq!(password.expose_secret(), "test password");
            true
        })
        .return_once(|id, _, _, _, _, _| {
            Ok(CreateDbClusterOutput::builder()
                .db_cluster(DbCluster::builder().db_cluster_identifier(id).build())
                .build())
        });

    mock_rds
        .expect_create_db_instance()
        .withf(|cluster, name, class, engine| {
            assert_eq!(cluster, "RustSDKCodeExamplesDBCluster");
            assert_eq!(name, "RustSDKCodeExamplesDBInstance");
            assert_eq!(class, "m5.large");
            assert_eq!(engine, "aurora-mysql");
            true
        })
        .return_once(|cluster, name, class, _| {
            Ok(CreateDbInstanceOutput::builder()
                .db_instance(
                    DbInstance::builder()
                        .db_cluster_identifier(cluster)
                        .db_instance_identifier(name)
                        .db_instance_class(class)
                        .build(),
                )
                .build())
        });

    mock_rds
        .expect_describe_db_clusters()
        .with(eq("RustSDKCodeExamplesDBCluster"))
        .times(1)
        .returning(|_| {
            Err(SdkError::service_error(
                DescribeDBClustersError::unhandled(Box::new(Error::new(
                    ErrorKind::Other,
                    "describe cluster error",
                ))),
                Response::new(StatusCode::try_from(400).unwrap(), SdkBody::empty()),
            ))
        })
        .with(eq("RustSDKCodeExamplesDBCluster"))
        .times(1)
        .returning(|id| {
            Ok(DescribeDbClustersOutput::builder()
                .db_clusters(DbCluster::builder().db_cluster_identifier(id).build())
                .build())
        });

    mock_rds.expect_describe_db_instance().return_once(|name| {
        Ok(DescribeDbInstancesOutput::builder()
            .db_instances(
                DbInstance::builder()
                    .db_instance_identifier(name)
                    .db_instance_status("Available")
                    .build(),
            )
            .build())
    });

    mock_rds
        .expect_describe_db_cluster_endpoints()
        .return_once(|_| {
            Ok(DescribeDbClusterEndpointsOutput::builder()
                .db_cluster_endpoints(DbClusterEndpoint::builder().status("available").build())
                .build())
        });

    let mut scenario = AuroraScenario::new(mock_rds);
    scenario.engine_version = Some("aurora-mysql8.0".into());
    scenario.instance_class = Some("m5.large".into());
    scenario.username = Some("test username".into());
    scenario.password = Some(SecretString::new("test password".into()));

    tokio::time::pause();
    let assertions = tokio::spawn(async move {
        let create = scenario.start_cluster_and_instance().await;
        assert!(create.is_ok());
    });

    tokio::time::advance(Duration::from_secs(1)).await;
    tokio::time::advance(Duration::from_secs(1)).await;
    tokio::time::resume();
    let _ = assertions.await;
}