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    Auto Scaling:AttachLoadBalancers

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    Auto Scaling:AttachLoadBalancers

    Last Updated:Sep 10, 2026

    Adds one or more load balancing instances.

    Operation description

    Operation description

    When you add load balancing instances to a scaling group, the following conditions must be met:

    • The load balancing instances and the scaling group must belong to the same Alibaba Cloud account and the same region.

    • The load balancing instances must be in the Running state.

    • The load balancing instances must have at least one listener configured and health checks must be enabled.

    • If both the load balancing instances and the scaling group are of the VPC network type, they must be in the same VPC.

    • If the scaling group is of the VPC network type and the load balancing instances are of the classic network type, and the backend servers of the load balancing instances include VPC-connected instances, those instances must be in the same VPC as the scaling group.

    • The number of load balancing instances associated with the scaling group cannot exceed the quota limit. For more information, see Limits.

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    RAM authorization

    No authorization for this operation. If you encounter issues with this operation, contact technical support.

    Request parameters

    Parameter

    Type

    Required

    Description

    Example
    ScalingGroupId

    string

    Yes

    The ID of the scaling group.

    asg-bp1avr6ensitts3w****
    ForceAttach

    boolean

    No

    Specifies whether to add all existing instances in the scaling group as backend servers of the load balancing CLB (formerly SLB) instances. Valid values:

    • true: All existing instances in the scaling group are added as backend servers of the load balancing instances when the load balancing instances are added to the scaling group.

      Note

      If a load balancing instance has already been added to the scaling group and you want to add all instances in the scaling group as backend servers of the load balancing instance, you can add the load balancing instance to the scaling group again with the ForceAttach parameter set to true.

    • false: Existing instances in the scaling group are not added as backend servers of the load balancing instances when the load balancing instances are added to the scaling group.

    Default value: false.

    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 and cannot exceed 64 characters in length. For more information, see How to ensure idempotence.

    123e4567-e89b-12d3-a456-42665544****
    Async

    boolean

    No

    Specifies whether to use asynchronous invocation when adding load balancing CLB (formerly SLB) instances. Asynchronous invocation ensures the transactional nature of the operation, which means that either all operations execute successfully or none of the operations take effect if one is failed. Use asynchronous invocation.

    Valid values:

    • true: Asynchronous invocation. The request returns the ID of the scaling activity.

    • false: Synchronous call.

    Default value: false.

    false
    LoadBalancer

    array

    No

    The IDs of the load balancing CLB (formerly SLB) instances to be added. Valid values of N: 1 to 5.

    lb-2zeur05gfs****

    string

    No

    The IDs of the load balancing CLB (formerly SLB) instances to be added. Valid values of N: 1 to 5.

    Note

    You can add up to five load balancing instances to a scaling group at a time.

    lb-2zeur05gfs****
    LoadBalancerConfig

    array<object>

    No

    The load balancing CLB (formerly SLB) configuration list.

    object

    No

    The load balancing CLB (formerly SLB) configuration list.

    LoadBalancerId

    string

    No

    The ID of the load balancing CLB (formerly SLB) instance.

    147b46d767c-cn-qingdao-cm5****
    Weight

    integer

    No

    The weight of an ECS instance or elastic container instance as a backend server after Auto Scaling adds the instance to the CLB server group. A higher weight indicates that the instance receives more requests. If the weight is 0, the instance does not receive any requests.

    Valid values: 0 to 100.

    10

    Response elements

    Element

    Type

    Description

    Example

    object

    ScalingActivityId

    string

    The ID of the scaling activity.

    This value is returned only when Async is set to true. You can call the DescribeScalingActivities operation to query the returned scaling activity ID and check the execution status of the scaling activity.

    asa-bp140qd7mak8k63f****
    RequestId

    string

    The request ID.

    473469C7-AA6F-4DC5-B3DB-A3DC0DE3****

    Examples

    Success response

    JSON format

    {
  "ScalingActivityId": "asa-bp140qd7mak8k63f****",
  "RequestId": "473469C7-AA6F-4DC5-B3DB-A3DC0DE3****"
}

    Error codes

    See Error Codes for a complete list.

    Release notes

    See Release Notes for a complete list.