Creating a Read Replica

Function

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

Learn how to authorize and 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	Project ID of a tenant in a region. To obtain this value, see Obtaining a Project ID.
instance_id	Yes	String	Instance ID, which is compliant with the UUID format.

Request Parameters

**Table 2** Request header parameters
Parameter	Mandatory	Type	Description
X-Auth-Token	Yes	String	User token. It can be obtained by calling the IAM API used to obtain a user token. The value of X-Subject-Token in the response header is the token value.
X-Language	No	String	Request language type. The default value is en-us. Values: en-us zh-cn

**Table 3** Request body parameters
Parameter	Mandatory	Type	Description
priorities	Yes	Array of integers	Failover priority of a read replica. Failover priority ranges from 1 for the first priority to 16 for the last 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 a 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.
is_auto_pay	No	String	Whether the order will be automatically paid after yearly/monthly instances are created. This parameter does not affect the payment method of automatic renewal. true: indicates the order will be automatically paid from your account. The default value is true. false: indicates the order will be manually paid.
availability_zones	No	Array of strings	AZ. You can specify an AZ to create a read replica. If this parameter is not specified, an AZ is automatically assigned by default. The function is in the open beta test (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.

Response Parameters

Status code: 201

**Table 4** Response body parameters
Parameter	Type	Description
instance_id	String	Instance ID.
node_names	Array of strings	Node names.
job_id	String	ID of the task for creating a read replica. This parameter is returned only when a pay-per-use read replica is created.
order_id	String	Order ID. This parameter is returned when yearly/monthly read replicas are created.

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"
}