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    Auto Scaling:ModifyScalingGroup

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    Auto Scaling:ModifyScalingGroup

    Last Updated:Sep 10, 2026

    If you need to automatically increase or decrease the number of instances of a specific type based on business changes and policies, you can configure a scaling group to automatically adjust your computing capacity (that is, the number of instances). If the current scaling group attributes no longer meet your business requirements, you can call the ModifyScalingGroup operation to modify scaling group attributes such as the maximum number of instances, minimum number of instances, or expected number of instances. This way, you do not need to create a scaling group again or reconfigure related attributes, which saves time and resources.

    Operation description

    • The following parameters cannot be modified:

      • RegionId.

      • LoadBalancerId.

      Note

      To modify the associated load balancing instances, use the AttachLoadBalancers and DetachLoadBalancers operations.

      • DBInstanceId.

      Note

      To modify the associated ApsaraDB RDS instances, use the AttachDBInstances and DetachDBInstances operations.

    • You can call this operation only when the scaling group is in the Active or Inactive state.

    • Enabling a new scaling configuration does not affect ECS instances or elastic container instances that were created based on the previous scaling configuration and are still running.

    • If you modify MaxSize and the number of ECS instances or elastic container instances in the scaling group exceeds the new MaxSize value, the scaling group automatically removes ECS instances or elastic container instances to make the instance count equal to MaxSize.

    • If you modify MinSize and the number of ECS instances or elastic container instances in the scaling group is less than the new MinSize value, the scaling group automatically adds ECS instances or elastic container instances to make the instance count equal to MinSize.

    • If DesiredCapacity is set for the scaling group and you modify DesiredCapacity, causing the number of ECS instances or elastic container instances in the scaling group to be inconsistent with the new DesiredCapacity value, the scaling group automatically adds or removes ECS instances or elastic container instances to make the instance count equal to DesiredCapacity.

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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

    ess:ModifyScalingGroup

    update

    *ScalingGroup

    acs:ess:{#regionId}:{#accountId}:scalinggroup/{#ScalingGroupId}

    		 None None

    Request parameters

    Parameter

    Type

    Required

    Description

    Example
    ScalingGroupId

    string

    Yes

    The ID of the scaling group that you want to modify.

    asg-bp1ffogfdauy0jw0****
    ScalingGroupName

    string

    No

    The name of the scaling group. The name must be unique within a region. The name must be 2 to 64 characters in length and must start with a digit, an uppercase letter, a lowercase letter, or a Chinese character. The name can contain digits, underscores (_), hyphens (-), and periods (.).

    scalinggroup****
    MinSize

    integer

    No

    The minimum number of ECS instances or elastic container instances in the scaling group. When the number of ECS or elastic container instances in the scaling group is less than the MinSize value, Auto Scaling performs automatic creation of ECS instances or elastic container instances.

    Note

    The value of MinSize must be less than or equal to the value of MaxSize.

    1
    MaxSize

    integer

    No

    The maximum number of ECS instances or elastic container instances in the scaling group. When the number of ECS or elastic container instances in the scaling group exceeds the MaxSize value, Auto Scaling automatically removes instances.

    The valid values of MaxSize depend on your Auto Scaling usage. Go to Quota Center to check the quota value for Maximum number of instances in a scaling group.

    For example, if the quota value for Maximum number of instances in a scaling group is 2000, the valid values of MaxSize are 0 to 2000.

    99
    DefaultCooldown

    integer

    No

    The default cooldown time of the scaling group. This parameter applies only to simple scaling. Valid values: 0 to 86400. Unit: seconds.

    During the cooldown time, the scaling group does not execute other scaling activities. This restriction applies only to scaling activities that are triggered by CloudMonitor event-triggered tasks.

    600
    RemovalPolicies

    array

    No

    The scale-in policy of the scaling group for removing ECS instances. Valid values:

    • OldestInstance: removes the ECS instance that was earliest added to the scaling group.

    • NewestInstance: removes the ECS instance that was most recently added to the scaling group.

    • OldestScalingConfiguration: removes the ECS instance that was created based on the earliest scaling configuration.

    string

    No

    The scale-in policy of the scaling group for removing ECS instances. Valid values:

    • OldestInstance: removes the ECS instance that was earliest added to the scaling group.

    • NewestInstance: removes the ECS instance that was most recently added to the scaling group.

    • OldestScalingConfiguration: removes the ECS instance that was created based on the earliest scaling configuration.

    NewestInstance
    ActiveScalingConfigurationId

    string

    No

    The ID of the active scaling configuration in the scaling group.

    asc-bp17pelvl720x5ub****
    HealthCheckType

    string

    No

    The health check mode of the scaling group. Valid values:

    • NONE: Health checks are disabled.

    • ECS: Health checks are performed on instances in the scaling group. This value is used to enable instance health checks for both ECS-type and ECI-type scaling groups.

    • LOAD_BALANCER: The health check status of instances is determined based on load balancing health check results. CLB-type load balancing is not supported. Default value: ECS.

    Note

    To enable both instance health checks and load balancing health checks, use the HealthCheckTypes parameter.

    ECS
    LaunchTemplateId

    string

    No

    The ID of the launch template. This parameter specifies the scaling group to obtain launch configuration information from the launch template.

    lt-m5e3ofjr1zn1aw7****
    LaunchTemplateVersion

    string

    No

    The version of the launch template. Valid values:

    • A fixed template version number.

    • Default: always uses the default version of the template.

    • Latest: always uses the latest version of the template.

    Default
    OnDemandBaseCapacity

    integer

    No

    The minimum number of pay-as-you-go instances required in the scaling group. Valid values: 0 to 1000. When the number of pay-as-you-go instances is less than this value, pay-as-you-go instances are preferentially created.

    When the MultiAZPolicy parameter is set to COMPOSABLE, the default value is 0.

    30
    OnDemandPercentageAboveBaseCapacity

    integer

    No

    The percentage of pay-as-you-go instances among the excess instances after the minimum number of pay-as-you-go instances (OnDemandBaseCapacity) is met. Valid values: 0 to 100.

    When the MultiAZPolicy parameter is set to COMPOSABLE, the default value is 100.

    20
    SpotInstanceRemedy

    boolean

    No

    Specifies whether to supplement spot instances. If this parameter is set to true, the scaling group attempts to create new instances to replace spot instances that are about to be reclaimed when the system sends reclamation notifications.

    true
    CompensateWithOnDemand

    boolean

    No

    Specifies whether to automatically create pay-as-you-go instances to meet the required number of ECS instances when spot instances cannot be created due to reasons such as cost or insufficient inventory. This parameter takes effect only when the MultiAZPolicy parameter of the CreateScalingGroup operation is set to COST_OPTIMIZED. Valid values:

    • true: Pay-as-you-go instances are allowed.

    • false: Pay-as-you-go instances are not allowed.

    true
    SpotInstancePools

    integer

    No

    The number of available instance types. The scaling group creates spot instances in a cost-effective manner across the specified instance types. Valid values: 0 to 10.

    When the MultiAZPolicy parameter is set to COMPOSABLE, the default value is 2.

    5
    DesiredCapacity

    integer

    No

    The expected number of ECS instances or elastic container instances in the scaling group. The scaling group automatically maintains the instance count at the expected number of instances. Valid values: MaxSize ≥ expected number of instances ≥ MinSize.

    Note

    If the expected number of instances feature is disabled and then re-enabled, you must set the DesiredCapacity value again.

    5
    GroupDeletionProtection

    boolean

    No

    Specifies whether to enable deletion protection for the scaling group. Valid values:

    • true: Deletion protection is enabled. The scaling group cannot be deleted.

    • false: Deletion protection is disabled.

    true
    MultiAZPolicy

    string

    No

    The scaling policy for ECS instances in a multi-zone scaling group. Valid values:

    • PRIORITY: Instances are scaled based on the priority of the vSwitches (VSwitchIds.N). Auto Scaling preferentially attempts to scale instances in the zone of the vSwitch with the highest priority. If the scaling fails, Auto Scaling attempts to scale instances in the zone of the vSwitch with the next highest priority.

    • COST_OPTIMIZED: During scale-out events, Auto Scaling attempts to create ECS instances in ascending order of vCPU unit price. During scale-in events, Auto Scaling attempts to remove ECS instances in descending order of vCPU unit price. When the scaling configuration specifies multiple instance types with the spot billing method, spot instances are preferentially created. You can use the CompensateWithOnDemand parameter to specify whether Auto Scaling automatically attempts to create pay-as-you-go instances when spot instances cannot be created.

    Note

    COST_OPTIMIZED takes effect only when the scaling configuration specifies multiple instance types or uses spot instances.

    • BALANCE: ECS instances are evenly allocated across the zones specified for the scaling group. If the zones become unbalanced due to reasons such as insufficient inventory, you can call the RebalanceInstance operation to rebalance resources.

    • COMPOSABLE: A composite policy that allows you to combine the preceding multi-zone scaling policies as needed.

    PRIORITY
    VSwitchIds

    array

    No

    The IDs of one or more vSwitches.

    This parameter takes effect only when the network type of the scaling group is VPC. The specified vSwitches must belong to the same VPC as the scaling group.

    The vSwitches can span multiple zones. The priority of vSwitches is sorted in ascending order of numbers, where 1 indicates the highest priority. When an ECS instance cannot be created in the zone of a higher-priority vSwitch, the system automatically selects the next-priority vSwitch to create the instance.

    string

    No

    The IDs of one or more vSwitches.

    This parameter takes effect only when the network type of the scaling group is VPC. The specified vSwitches must belong to the same VPC as the scaling group.

    The vSwitches can span multiple zones. The priority of vSwitches is sorted in ascending order of numbers, where 1 indicates the highest priority. When an ECS instance cannot be created in the zone of a higher-priority vSwitch, the system automatically selects the next-priority vSwitch to create the instance.

    vsw-bp1oo2a7isyrb8igf****
    LaunchTemplateOverrides

    array<object>

    No

    The instance type information for the extended launch template.

    object

    No

    The instance type information for the extended launch template.

    InstanceType

    string

    No

    To enable the scaling group to scale based on the capacity of instance types, specify both this parameter and LaunchTemplateOverrides.WeightedCapacity.

    This parameter specifies the instance type and overrides the instance type in the launch template.

    Note

    This parameter takes effect only when the LaunchTemplateId parameter specifies a launch template.

    Valid values of InstanceType: ECS instance types that are available for purchase.

    ecs.c5.xlarge

    WeightedCapacity

    integer

    No

    To enable the scaling group to scale based on the capacity of instance types, specify this parameter after you specify LaunchTemplateOverrides.InstanceType. The two parameters have a one-to-one correspondence.

    This parameter specifies the weight of the instance type, which represents the capacity of a single instance of this type in the scaling group.

    A larger weight means that fewer instances of this type are required to meet the expected capacity.

    Because instance types differ in performance metrics such as the number of vCPUs and memory size, you can assign different weights to different instance types based on your requirements.

    Example:

    • Current capacity: 0.

    • Expected capacity: 6.

    • Capacity of ecs.c5.xlarge: 4.

    To meet the expected capacity, the scaling group scales out two ecs.c5.xlarge instances.

    Note

    During a scale-out event, the capacity of the scaling group cannot exceed the sum of MaxSize and the maximum weight of the instance types.

    Valid values of WeightedCapacity: 1 to 500.

    4
    SpotPriceLimit

    number

    No

    The maximum hourly price for the instance type specified by LaunchTemplateOverride.N.InstanceType. You can specify N values for this parameter. The extended launch template supports N instance types. Valid values of N: 1 to 20.

    Note

    This parameter takes effect only when the LaunchTemplateId parameter specifies a launch template.

    0.025
    MaxInstanceLifetime

    integer

    No

    The maximum amount of time that an instance can remain in the scaling group. Unit: seconds.

    Valid values: 0 or [86400, Integer.maxValue]. A value of 0 clears the previously set MaxInstanceLifetime value (that is, MaxInstanceLifetime is not set).

    Default value: null.

    Note

    This parameter is not supported for ECI-type scaling groups or scaling groups with the economical mode enabled.

    86400
    AzBalance

    boolean

    No

    Specifies whether the capacity of the scaling group is evenly distributed across zones. This parameter takes effect only when the MultiAZPolicy parameter is set to COMPOSABLE. Valid values:

    • true: The capacity of the scaling group is evenly distributed across zones.

    • false: The capacity of the scaling group is not evenly distributed across zones.

    Default value: false.

    false
    AllocationStrategy

    string

    No

    The capacity allocation strategy that determines how the scaling group selects available instance types to meet capacity requirements. The capacity allocation strategy applies to both pay-as-you-go and spot capacity. This parameter takes effect only when the MultiAZPolicy parameter is set to COMPOSABLE. Valid values:

    • priority: Instances are created in the order of the configured instance types.

    • lowestPrice: Instances are created in ascending order of vCPU unit price.

    Default value: priority.

    priority
    SpotAllocationStrategy

    string

    No

    The allocation strategy for spot capacity. You can use this parameter to separately specify the allocation strategy for spot capacity. This parameter takes effect only when the MultiAZPolicy parameter is set to COMPOSABLE. Valid values:

    • priority: Instances are created in the order of the configured instance types.

    • lowestPrice: Instances are created in ascending order of vCPU unit price.

    Default value: priority.

    lowestPrice
    CustomPolicyARN

    string

    No

    The Alibaba Cloud Resource Name (ARN) of the custom scale-in policy (Function). This parameter takes effect only when the first removal policy in RemovalPolicies is set to CustomPolicy.

    acs:fc:cn-zhangjiakou:16145688****:services/ess_custom_terminate_policy.LATEST/functions/ess_custom_terminate_policy_name
    DisableDesiredCapacity

    boolean

    No

    Specifies whether to disable the expected number of instances feature for the scaling group. Valid values:

    • false: The expected number of instances feature is enabled.

    • true: The expected number of instances feature is disabled.

    Note

    You can set this parameter to true (to disable the expected number of instances feature) only when no scaling activity is in progress in the scaling group. When the expected number of instances feature is disabled, the current DesiredCapacity attribute of the scaling group is cleared, but the current number of instances in the scaling group remains unchanged.

    false
    ScalingPolicy

    string

    No

    The reclaim pattern of the scaling group. Valid values:

    • recycle: The reclaim pattern is set to Shutdown and Reclaim Mode.

    • release: The reclaim pattern is set to Release Mode.

    • forcerelease: The reclaim pattern is set to Force Release Mode.

      Note

      If you select forcerelease, the system forcefully releases instances that are in the Running state during scale-down activities. Forcefully releasing an instance is equivalent to a power-off operation, which erases temporary data in the memory and storage of the instance. The data cannot be recovered. Proceed with caution.

    • forcerecycle: The reclaim pattern is set to Force Shutdown and Reclaim Mode.

      Note

      If you select forcerecycle, the system forcefully shuts down instances that are in the Running state during scale-down activities. Forcefully shutting down an instance is equivalent to a power-off operation, which erases temporary data in the memory and storage of the instance. The data cannot be recovered. Proceed with caution.

    ScalingPolicy specifies the reclaim pattern of the scaling group. The specific action taken when an instance is removed from the scaling group is determined by the RemovePolicy parameter of RemoveInstances. For more information, see RemoveInstances.

    recycle
    HealthCheckTypes

    array

    No

    The health check modes of the scaling group.

    Note

    You can set multiple values for this parameter to enable multiple health check options. If the HealthCheckType parameter is set, this parameter is ignored.

    string

    No

    The list of health check modes for the scaling group. Valid values:

    • NONE: Health checks are disabled.

    • ECS: Health checks are performed on instances in the scaling group. This value is used to enable instance health checks for both ECS-type and ECI-type scaling groups.

    • LOAD_BALANCER: The health check status of instances is determined based on load balancing health check results. CLB-type load balancing is not supported.

    Default value: ECS.

    ECS
    StopInstanceTimeout

    integer

    No

    The timeout period for waiting for an ECS instance to be stopped during a scale-in process. Unit: seconds. Valid values: 30 to 240.

    Note

    • This parameter takes effect only during scale-in processes when ScalingPolicy is set to release.

    • If this parameter is set, the system waits up to the StopInstanceTimeout period for the instance to stop. After the timeout period elapses, the scale-in process continues regardless of whether the instance is stopped.

    • If this parameter is not set, the system waits until the instance is stopped. The scale-in process continues only after the instance is stopped. If the instance fails to stop, the scale-in process is rolled back and the scale-in fails.

    • If this parameter is set to 0, the parameter settings are cleared.

    60
    CapacityOptions

    object

    No

    The capacity options.

    OnDemandBaseCapacity

    integer

    No

    The minimum number of pay-as-you-go instances required in the scaling group. When the number of pay-as-you-go instances in the scaling group is less than this value, the system preferentially creates pay-as-you-go instances. Valid values: 0 to 1000.

    When the MultiAZPolicy parameter is set to COMPOSABLE, the default value is 0.

    30
    OnDemandPercentageAboveBaseCapacity

    integer

    No

    The percentage of pay-as-you-go instances among the excess instances after the minimum number of pay-as-you-go instances (OnDemandBaseCapacity) is met. Valid values: 0 to 100.

    When the MultiAZPolicy parameter is set to COMPOSABLE, the default value is 100.

    20
    CompensateWithOnDemand

    boolean

    No

    Specifies whether to automatically create pay-as-you-go instances to meet the required number of ECS instances when spot instances cannot be created due to reasons such as cost or insufficient inventory. This parameter takes effect only when the MultiAZPolicy parameter of the CreateScalingGroup operation is set to COST_OPTIMIZED. Valid values:

    • true: Pay-as-you-go instances are allowed.

    • false: Pay-as-you-go instances are not allowed.

    true
    SpotAutoReplaceOnDemand

    boolean

    No

    Specifies whether to use spot instances to replace pay-as-you-go instances when the pay-as-you-go ratio exceeds the OnDemandPercentageAboveBaseCapacity ratio after CompensateWithOnDemand is enabled. A common scenario is when CompensateWithOnDemand causes spot instances to be downgraded to pay-as-you-go instances due to spot inventory or pricing issues. To prevent pay-as-you-go instances from persisting for an extended period, the system attempts to replace the excess pay-as-you-go capacity with spot instances. Valid values:

    • true: Replacement is allowed.

    • false: Replacement is not allowed.

    Default value: false.

    true
    PriceComparisonMode

    string

    No

    The price comparison mode for the cost optimization strategy of the scaling group. Valid values:

    • PricePerUnit: Prices are compared based on the price per unit of capacity.

      The capacity of an instance in the scaling group equals the weight assigned to the instance type. The default weight is 1, meaning one ECS instance occupies a capacity of 1.

    • PricePerVCpu: Prices are compared based on the price per vCPU.

    Default value: PricePerUnit.

    PricePerUnit
    BalanceMode

    string

    No

    The zone balance mode. This parameter takes effect only when zone balancing is enabled. Valid values:

    • BalancedBestEffort: When resource creation fails in a zone, the system falls back to other zones to ensure best-effort resource delivery.

    • BalancedOnly: When resource creation fails in a zone, the system does not fall back to other zones. The scale-out activity partially succeeds to prevent excessive imbalance of resources across zones.

    Default value: BalancedBestEffort.

    BalancedBestEffort
    AutoRebalance

    boolean

    No

    Specifies whether to enable automatic rebalancing for the scaling group. This parameter takes effect only when BalancedOnly is enabled for a zone-balanced scaling group. Valid values:

    • false: Automatic rebalancing is disabled.

    • true: When automatic rebalancing is enabled, the scaling group automatically monitors the capacity across zones. When the capacity is unbalanced across zones, the scaling group proactively scales in and out across zones to rebalance the capacity.

    Default value: false.

    false

    Response elements

    Element

    Type

    Description

    Example

    object

    RequestId

    string

    The request ID.

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

    Examples

    Success response

    JSON format

    {
  "RequestId": "473469C7-AA6F-4DC5-B3DB-A3DC0DE3****"
}

    Error codes

    See Error Codes for a complete list.

    Release notes

    See Release Notes for a complete list.