Updated on 2026-03-16 GMT+08:00

Creating a Read Replica

Function

This API is used to create a read replica. Before calling this API:

Learn how to authenticate it.
Obtain the required region and endpoint.

URI

POST /v3/{project_id}/instances/{instance_id}/nodes/enlarge

**Table 1** URI parameters
Parameter	Mandatory	Type	Description
project_id	Yes	String	Definition Project ID of a tenant in a region. To obtain this value, see Obtaining a Project ID. Constraints N/A Range The value contains 32 characters. Only letters and digits are allowed. Default Value N/A
instance_id	Yes	String	Definition Instance ID, which uniquely identifies an instance. Constraints N/A Range The value contains 36 characters with a suffix of in07. Only letters and digits are allowed. Default Value N/A

Request Parameters

**Table 2** Request header parameters
Parameter	Mandatory	Type	Description
X-Auth-Token	Yes	String	Definition User token. To obtain this value, call the IAM API for obtaining a user token. The value of X-Subject-Token in the response header is the token value. Constraints N/A Range N/A Default Value N/A
X-Language	No	String	Definition Request language type. Constraints N/A Range en-us zh-cn Default Value en-us

**Table 3** Request body parameters
Parameter	Mandatory	Type	Description
priorities	Yes	Array of integers	Definition Failover priority of a read replica. A smaller value indicates a higher priority. This priority determines the order in which read replicas are promoted when recovering from a primary node failure. Read replicas with the same priority have the same probability of being promoted to the new primary node. You can configure a failover priority for up to 9 read replicas, and the default priority for the remaining read replicas is -1, indicating these read replicas cannot be promoted to primary. You can change the failover priority of a read replica. Constraints N/A Range 1–16 Default Value N/A
is_auto_pay	No	String	Definition Whether the order will be automatically paid. Constraints This parameter is only available for yearly/monthly instances. It does not affect the payment mode of automatic renewal. Range true: The order will be automatically paid. false: The order will be manually paid. Default Value true
availability_zones	No	Array of strings	Definition AZ. You can specify an AZ to create a read replica. If this parameter is not specified, an AZ is automatically assigned by default. Constraints The parameter is in the OBT phase. To use it, submit a service ticket. To obtain the value, see the key availability_zone in az_status of Querying Database Specifications. Note: Creating a read replica in a specified AZ may fail due to insufficient resources. Range To obtain the value, see the key availability_zone in az_status of Querying Database Specifications. Default Value N/A

Response Parameters

Status code: 201

**Table 4** Response body parameters
Parameter	Type	Description
instance_id	String	Definition Instance ID, which uniquely identifies an instance. Range N/A
node_names	Array of strings	Definition Node names.
job_id	String	Definition ID of the task for creating a read replica. This parameter is only returned for pay-per-use read replicas. Range N/A
order_id	String	Definition Order ID. This parameter is only returned for yearly/monthly read replicas. Range N/A

Status code: 400

**Table 5** Response body parameters
Parameter	Type	Description
error_code	String	Error code.
error_msg	String	Error message.

Status code: 500

**Table 6** Response body parameters
Parameter	Type	Description
error_code	String	Error code.
error_msg	String	Error message.

Example Request

Creating a read replica for a DB instance

POST https://{endpoint}/v3/054e292c9880d4992f02c0196d3ea468/instances/ba62a0b83a1b42bfab275829d86ac0fdin07/nodes/enlarge
{
  "priorities" : [ 1, 2 ]
}

Example Response

Status code: 201

Success.

{
  "instance_id" : "ba62a0b83a1b42bfab275829d86ac0fdin07",
  "node_names" : [ "gauss-ccf5_node03" ],
  "job_id" : "dff1d289-4d03-4942-8b9f-463ea07c000d"
}

Status Code

For details, see Status Codes.

Error Code

For details, see Error Codes.

Parent topic: Instance Management