Adding a Backend Server

Updated on 2025-02-25 GMT+08:00

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Function

This API is used to add a backend server.

Constraints

When you add backend servers, note the following:

Two backend servers in the same backend server group must have different IP addresses and ports.
If no subnets are specified during cloud server creation, IP as backend servers can be added. In this case, address must be set to an IPv4 address, the protocol of the backend server group must be TCP, HTTP, or HTTPS, and IP as a Backend must have been enabled for the load balancer.
If a subnet is specified during cloud server creation, the subnet must be in the same VPC where the load balancer resides.
If the backend server group supports IPv4/IPv6 dual stack, address can be an IPv4 address or an IPv6 address. If the backend server group supports only IPv4, address can only be an IPv4 address.
If type of the backend server is set to instance, address must be a private IP address that is not used by any load balancer.

Calling Method

For details, see Calling APIs.

URI

POST /v3/{project_id}/elb/pools/{pool_id}/members

**Table 1** Path Parameters
Parameter	Mandatory	Type	Description
pool_id	Yes	String	Specifies the ID of the backend server group.
project_id	Yes	String	Specifies the project ID.

Request Parameters

**Table 2** Request header parameters
Parameter	Mandatory	Type	Description
X-Auth-Token	Yes	String	Specifies the token used for IAM authentication.

**Table 3** Request body parameters
Parameter	Mandatory	Type	Description
member	Yes	CreateMemberOption object	Specifies the backend server.

**Table 4** CreateMemberOption
Parameter	Mandatory	Type	Description
address	Yes	String	Specifies the private IP address bound to the backend server. Note: If subnet_cidr_id is left blank, IP as a Backend is enabled. In this case, the IP address must be an IPv4 address. If subnet_cidr_id is not left blank, the IP address version can be IPv4 or IPv6. It must be in the subnet specified by subnet_cidr_id.
admin_state_up	No	Boolean	Specifies the administrative status of the backend server. The value can be true or false. Although this parameter can be used in the APIs for creating and updating backend servers, its actual value depends on whether ECSs exist. If ECSs exist, the value is true. Otherwise, the value is false.
name	No	String	Specifies the backend server name. Note: The name is not an ECS name. If this parameter is not specified, an empty value will be returned.
project_id	No	String	Specifies the project ID.
protocol_port	No	Integer	Specifies the port used by the backend server to receive requests. Note: This parameter can be left blank because it does not take effect if any_port_enable is set to true for a backend server group.
subnet_cidr_id	No	String	Specifies the ID of the IPv4 or IPv6 subnet where the backend server resides. neutron_subnet_id defines IPv4 subnets, and neutron_network_id defines IPv6 subnets. You can query parameters neutron_subnet_id and neutron_network_id in the response by calling the API GET https://{VPC_Endpoint}/v1/{project_id}/subnets to get the IPv4 subnet ID and IPv6 subnet ID respectively. Note: The IPv4 or IPv6 subnet must be in the same VPC as the subnet of the load balancer. If ip_target_enable is set to true, this parameter can be left blank. In this case, IP as backend servers must use private IPv4 addresses, and the protocol of the backend server group must be TCP, UDP, TLS, HTTP, HTTPS, QUIC, or GRPC. If ip_target_enable is set to false, this parameter must be specified.
weight	No	Integer	Specifies the weight of the backend server. Requests are routed to backend servers in the same backend server group based on their weights. The value ranges from 0 to 100, and the default value is 1. The larger the weight is, the higher proportion of requests the backend server receives. If the weight is set to 0, the backend server will not accept new requests. If lb_algorithm is set to SOURCE_IP or QUIC_CID, this parameter will not take effect.

Response Parameters

Status code: 201

**Table 5** Response body parameters
Parameter	Type	Description
request_id	String	Specifies the request ID. Note: The value is automatically generated.
member	Member object	Specifies the backend server.

**Table 6** Member
Parameter	Type	Description
id	String	Specifies the backend server ID. Note: The value of this parameter is not the ID of the server but an ID automatically generated for the backend server that has already been associated with the load balancer.
name	String	Specifies the backend server name. Note: The name is not an ECS name.
project_id	String	Specifies the project ID of the backend server.
admin_state_up	Boolean	Specifies the administrative status of the backend server. The value can be true or false. Although this parameter can be used in the APIs for creating and updating backend servers, its actual value depends on whether ECSs exist. If ECSs exist, the value is true. Otherwise, the value is false.
subnet_cidr_id	String	Specifies the ID of the IPv4 or IPv6 subnet where the backend server resides. neutron_subnet_id defines IPv4 subnets, and neutron_network_id defines IPv6 subnets. You can query parameters neutron_subnet_id and neutron_network_id in the response by calling the API GET https://{VPC_Endpoint}/v1/{project_id}/subnets to get the IPv4 subnet ID and IPv6 subnet ID respectively. Note: The IPv4 or IPv6 subnet must be in the same VPC as the subnet of the load balancer. If ip_target_enable is set to true, this parameter can be left blank. In this case, IP as backend servers must use private IPv4 addresses, and the protocol of the backend server group must be TCP, UDP, TLS, HTTP, HTTPS, QUIC, or GRPC. If ip_target_enable is set to false, this parameter must be specified.
protocol_port	Integer	Specifies the port used by the backend server to receive requests. Note: This parameter can be left blank because it does not take effect if any_port_enable is set to true for a backend server group.
weight	Integer	Specifies the weight of the backend server. Requests are routed to backend servers in the same backend server group based on their weights. The value ranges from 0 to 100, and the default value is 1. The larger the weight is, the higher proportion of requests the backend server receives. If the weight is set to 0, the backend server will not accept new requests. If lb_algorithm is set to SOURCE_IP or QUIC_CID, this parameter will not take effect.
address	String	Specifies the private IP address bound to the backend server. Note: If subnet_cidr_id is left blank, IP as a Backend is enabled. In this case, the IP address must be an IPv4 address. If subnet_cidr_id is not left blank, the IP address can be IPv4 or IPv6. It must be in the subnet specified by subnet_cidr_id.
ip_version	String	Specifies the IP version supported by the backend server. The value can be v4 (IPv4) or v6 (IPv6), depending on the value of address returned by the system.
operating_status	String	Specifies the health status of the backend server if listener_id under status is not specified. Value options: ONLINE: The backend server is running normally. NO_MONITOR: No health check is configured for the backend server group to which the backend server belongs. OFFLINE: The cloud server used as the backend server is stopped or does not exist.
status	Array of MemberStatus objects	Specifies the health status of the backend server if listener_id under status is specified. If listener_id under status is not specified, operating_status of member takes precedence.
reason	MemberHealthCheckFailedReason object	Specifies why health check fails.
created_at	String	Specifies the time when the backend server was added. The format is yyyy-MM-dd'T'HH:mm:ss'Z' (UTC time). This is a new field in this version, and it will not be returned for resources associated with existing dedicated load balancers and for resources associated with existing and new shared load balancers.
updated_at	String	Specifies the time when the backend server was updated. The format is yyyy-MM-dd'T'HH:mm:ss'Z' (UTC time). This is a new field in this version, and it will not be returned for resources associated with existing dedicated load balancers and for resources associated with existing and new shared load balancers.
member_type	String	Specifies the type of the backend server. Value options: ip: IP as backend servers instance: ECSs used as backend servers
instance_id	String	Specifies the ID of the instance associated with the backend server. If this parameter is left blank, the backend server is not a real device. It may be an IP address.

**Table 7** MemberStatus
Parameter	Type	Description
listener_id	String	Specifies the listener ID.
operating_status	String	Specifies the health status of the backend server. Value options: ONLINE: The backend server is running normally. NO_MONITOR: No health check is configured for the backend server group to which the backend server belongs. OFFLINE: The cloud server used as the backend server is stopped or does not exist.
reason	MemberHealthCheckFailedReason object	Specifies why health check fails.

**Table 8** MemberHealthCheckFailedReason
Parameter	Type	Description
reason_code	String	Specifies the code of the health check failures. Value options: CONNECT_TIMEOUT: The connection with the backend server times out during a health check. CONNECT_REFUSED: The load balancer rejects connections with the backend server during a health check. CONNECT_FAILED: The load balancer fails to establish connections with the backend server during a health check. CONNECT_INTERRUPT: The load balancer is disconnected from the backend server during a health check. SSL_HANDSHAKE_ERROR: The SSL handshakes with the backend server fail during a health check. RECV_RESPONSE_FAILED: The load balancer fails to receive responses from the backend server during a health check. RECV_RESPONSE_TIMEOUT: The load balancer does not receive responses from the backend server within the timeout duration during a health check. SEND_REQUEST_FAILED: The load balancer fails to send a health check request to the backend server during a health check. SEND_REQUEST_TIMEOUT: The load balancer fails to send a health check request to the backend server within the timeout duration. RESPONSE_FORMAT_ERROR: The load balancer receives invalid responses from the backend server during a health check. RESPONSE_MISMATCH: The response code received from the backend server is different from the preset code.
expected_response	String	Specifies the expected HTTP status code. This parameter will take effect only when type is set to HTTP, HTTPS, or GRPC. The status code cannot be null if reason_code is RESPONSE_MISMATCH. Value ranges: A specific status code. If type is set to GRPC, the status code ranges from 0 to 99. If type is set to other values, the status code ranges from 200 to 599. For example, the status code can be 0 or 200. A list of status codes that are separated with commas (,), for example, 200,202 or 0,1. A maximum of five status codes are supported. A status code range. Different ranges are separated with commas (,), for example, 200-204,300-399 or 0-5,10-12,20-30. A maximum of five ranges are supported.
healthcheck_response	String	Specifies the returned HTTP status code in the response. This parameter will take effect only when type is set to HTTP, HTTPS, or GRPC. The status code cannot be null if reason_code is RESPONSE_MISMATCH. Value range: A specific status code. If type is set to GRPC, the status code ranges from 0 to 99. If type is set to other values, the status code ranges from 200 to 599. For example, the status code can be 0 or 200.

Example Requests

Example 1: Adding a backend server

POST https://{ELB_Endpoint}/v3/99a3fff0d03c428eac3678da6a7d0f24/elb/pools/36ce7086-a496-4666-9064-5ba0e6840c75/members

{
  "member" : {
    "subnet_cidr_id" : "c09f620e-3492-4429-ac15-445d5dd9ca74",
    "protocol_port" : 89,
    "name" : "My member",
    "address" : "120.10.10.16"
  }
}

Example 2: Adding an IP address as a backend server

POST https://{ELB_Endpoint}/v3/99a3fff0d03c428eac3678da6a7d0f24/elb/pools/36ce7086-a496-4666-9064-5ba0e6840c75/members

{
  "member" : {
    "protocol_port" : 89,
    "name" : "My member",
    "address" : "120.10.10.16"
  }
}

Example Responses

Status code: 201

Normal response to POST requests.

{
  "member" : {
    "name" : "My member",
    "weight" : 1,
    "admin_state_up" : false,
    "subnet_cidr_id" : "c09f620e-3492-4429-ac15-445d5dd9ca74",
    "project_id" : "99a3fff0d03c428eac3678da6a7d0f24",
    "address" : "120.10.10.16",
    "protocol_port" : 89,
    "id" : "1923923e-fe8a-484f-bdbc-e11559b1f48f",
    "operating_status" : "NO_MONITOR",
    "status" : [ {
      "listener_id" : "427eee03-b569-4d6c-b1f1-712032f7ec2d",
      "operating_status" : "NO_MONITOR"
    } ],
    "ip_version" : "v4"
  },
  "request_id" : "f354090d-41db-41e0-89c6-7a943ec50792"
}