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Server Load Balancer:UpdateServerGroupAttribute

Last Updated:Dec 22, 2025

Updates the configurations of a Network Load Balancer (NLB) server group.

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RAM authorization

The table below describes the authorization required to call this API. You can define it in a Resource Access Management (RAM) policy. The table's columns are detailed below:

  • Action: The actions can be used in the Action element of RAM permission policy statements to grant permissions to perform the operation.

  • API: The API that you can call to perform the action.

  • Access level: The predefined level of access granted for each API. Valid values: create, list, get, update, and delete.

  • Resource type: The type of the resource that supports authorization to perform the action. It indicates if the action supports resource-level permission. The specified resource must be compatible with the action. Otherwise, the policy will be ineffective.

    • For APIs with resource-level permissions, required resource types are marked with an asterisk (*). Specify the corresponding Alibaba Cloud Resource Name (ARN) in the Resource element of the policy.

    • For APIs without resource-level permissions, it is shown as All Resources. Use an asterisk (*) in the Resource element of the policy.

  • Condition key: The condition keys defined by the service. The key allows for granular control, applying to either actions alone or actions associated with specific resources. In addition to service-specific condition keys, Alibaba Cloud provides a set of common condition keys applicable across all RAM-supported services.

  • Dependent action: The dependent actions required to run the action. To complete the action, the RAM user or the RAM role must have the permissions to perform all dependent actions.

Action

Access level

Resource type

Condition key

Dependent action

nlb:UpdateServerGroupAttribute

update

*ServerGroup

acs:nlb:{#regionId}:{#accountId}:servergroup/{#ServerGroupId}

None None

Request parameters

Parameter

Type

Required

Description

Example

ServerGroupId

string

Yes

The ID of the server group.

sgp-atstuj3rtoptyui****

ServerGroupName

string

No

The new name of the server group.

The name must be 2 to 128 characters in length, start with a letter, and can contain digits, periods (.), underscores (_), and hyphens (-).

NLB_ServerGroup1

ConnectionDrainEnabled

boolean

No

Specifies whether to enable connection draining. Valid values:

  • true

  • false

false

ConnectionDrainTimeout

integer

No

The timeout period of connection draining. Unit: seconds. Valid values: 0 to 900.

10

Scheduler

string

No

The scheduling algorithm. Valid values:

  • Wrr: weighted round-robin. Backend servers with higher weights receive more requests.

  • Wlc: weighted least connections. Requests are distributed based on the weight and the number of connections to each backend server. If the weights are the same, the backend server with the fewest connections receives more requests.

  • rr: round-robin. Requests are distributed to backend servers in sequence.

  • sch: source IP hash. Requests from the same source IP address are distributed to the same backend server.

  • tch: four-tuple hash. Requests are distributed to backend servers based on a hash of the four-tuple, which consists of the source IP address, destination IP address, source port, and destination port. This ensures that requests from the same stream are sent to the same backend server.

  • qch: QUIC ID hash. Requests with the same QUIC ID are hashed to the same backend server.

Note

This scheduling algorithm is available only when the backend protocol is UDP.

Wrr

PreserveClientIpEnabled

boolean

No

Specifies whether to enable client IP preservation. Valid values:

  • true

  • false

Note

If PreserveClientIpEnabled is set to false and the server group is associated with a TCPSSL listener, you cannot change the value to true.

false

HealthCheckConfig

object

No

The health check configurations.

HealthCheckEnabled

boolean

No

Specifies whether to enable health checks. Valid values:

  • true

  • false

false

HealthCheckType

string

No

The health check protocol. Valid values:

  • TCP

  • HTTP

  • UDP

TCP

HealthCheckConnectPort

integer

No

The port that is used for health checks on backend servers. Valid values: 0 to 65535. A value of 0 indicates that the port of the backend server is used for health checks.

0

HealthyThreshold

integer

No

The number of consecutive successful health checks that must occur before a backend server is declared healthy. Valid values: 2 to 10.

3

UnhealthyThreshold

integer

No

The number of consecutive failed health checks that must occur before a backend server is declared unhealthy. Valid values: 2 to 10.

3

HealthCheckConnectTimeout

integer

No

The maximum response time for a health check. Unit: seconds. Valid values: 1 to 300. Default value: 5.

100

HealthCheckInterval

integer

No

The interval between two consecutive health checks. Unit: seconds. Default value: 5.

  • If HealthCheckType is set to TCP or HTTP, the value must be in the range of 1 to 50.

  • If HealthCheckType is set to UDP, the value must be in the range of 1 to 300. Set the interval to a value greater than or equal to the response timeout period. This prevents UDP probe packets from being marked as unresponsive due to timeouts.

5

HealthCheckDomain

string

No

The domain name that is used for health checks. Valid values:

  • $SERVER_IP: The private IP address of the backend server.

  • domain: A specific domain name. The domain name must be 1 to 80 characters in length and can contain only lowercase letters, digits, hyphens (-), and periods (.).

Note

This parameter takes effect only when HealthCheckType is set to HTTP.

$SERVER_IP

HealthCheckUrl

string

No

The path that is used for health checks.

The path must be 1 to 80 characters in length. It can contain letters, digits, and the characters -/.%?#&=. It can also contain the extended characters _;~!()*[]@$^:',+. The path must start with a forward slash (/).

Note

This parameter takes effect only when HealthCheckType is set to HTTP.

/test/index.html

HealthCheckHttpCode

array

No

The HTTP status codes that indicate a healthy state. You can specify multiple HTTP status codes. Separate them with commas (,). Valid values: http_2xx (default), http_3xx, http_4xx, and http_5xx.

Note

This parameter takes effect only when HealthCheckType is set to HTTP.

string

No

The HTTP status codes that indicate a healthy state. You can specify multiple HTTP status codes. Separate them with commas (,). Valid values: http_2xx (default), http_3xx, http_4xx, and http_5xx.

Note

This parameter takes effect only when HealthCheckType is set to HTTP.

http_2xx

HttpCheckMethod

string

No

The health check method. Valid values: GET or HEAD.

Note

This parameter takes effect only when HealthCheckType is set to HTTP.

GET

HealthCheckReq

string

No

The request string for UDP health checks. The string can contain only letters and digits. The string must be up to 512 characters in length.

hello

HealthCheckExp

string

No

The response string for UDP health checks. The string can contain only letters and digits. The string must be up to 512 characters in length.

ok

HealthCheckHttpVersion

string

No

The HTTP version for health checks. Valid values: HTTP1.0 or HTTP1.1.

Note

This parameter takes effect only when HealthCheckType is set to HTTP.

HTTP1.0

RegionId

string

No

The ID of the region where the NLB instance is deployed.

You can call the DescribeRegions operation to query the most recent region list.

cn-hangzhou

DryRun

boolean

No

Specifies whether to perform a dry run. Valid values:

  • true: sends a check request without updating the server group information. The system checks the required parameters, request format, and service limits. If the check fails, the corresponding error is returned. If the check succeeds, the DryRunOperation error code is returned.

  • false (default): sends a normal request. After the request passes the check, a 2xx HTTP status code is returned and the operation is performed.

false

ClientToken

string

No

The client token that is used to ensure the idempotence of the request.

You can use the client to generate the token, but you must make sure that the token is unique among different requests. The token can contain only ASCII characters.

Note

If you do not specify this parameter, the system automatically uses the RequestId of the API request as the ClientToken. The RequestId may be different for each API request.

123e4567-e89b-12d3-a456-426655440000

Response elements

Element

Type

Description

Example

object

The configurations of the server group.

RequestId

string

The request ID.

54B48E3D-DF70-471B-AA93-08E683A1B45

ServerGroupId

string

The ID of the server group.

sgp-atstuj3rtoptyui****

JobId

string

The ID of the asynchronous task.

72dcd26b-f12d-4c27-b3af-18f6aed5****

Examples

Success response

JSON format

{
  "RequestId": "54B48E3D-DF70-471B-AA93-08E683A1B45",
  "ServerGroupId": "sgp-atstuj3rtoptyui****",
  "JobId": "72dcd26b-f12d-4c27-b3af-18f6aed5****"
}

Error codes

HTTP status code

Error code

Error message

Description

400 IllegalParam.%s The param of %s is illegal.
400 SystemBusy System is busy, please try again later.
400 IllegalParam.healthCheckDomain The parameter of healthCheckConfig.healthCheckDomain is illegal. The healthCheckDomain in the health check configuration is invalid. Check the input parameters.
400 IlleagalParam.healthCheckUrl The parameter of healthCheckUrl in healthCheckConfig is illegal. The URL of the health check used in the health check setting is invalid.
400 OperationDenied.UidNotAllowQuic29 The operation is not allowed because of uid not allow quic29 version.
400 IllegalParam The param of %s is illegal.
400 DryRunOperation Request validation has been passed with DryRun flag set. Request validation has been passed with DryRun flag set.
400 IllegalParam.ServerGroupName The param of ServerGroupName is illegal.
400 IllegalParam.PreserveClientIpSwitch The server group associated with the tcpssl listener does not support enabling PreserveClientIp. The server group associated with the tcpssl listener does not support enabling PreserveClientIp.
403 Forbidden.NoPermission Authentication is failed for NoPermission. Authentication is failed for NoPermission.
404 ResourceNotFound.serverGroup The specified resource of serverGroup is not found. The specified resource of serverGroup is not found. Please check the input parameters.

See Error Codes for a complete list.

Release notes

See Release Notes for a complete list.