能否在同一CloudFormation模板中同时配置ASG动态与预测扩展？

报错信息 #

Resource handler returned message: "You can't specify PredictiveScalingConfiguration for policy type: TargetTrackingScaling (Service: AutoScaling, Status Code: 400, Request ID: bd851c95-ad78-4afc-979b-f5e2e5bf188a)" (RequestToken: 387601f6-9734-ac0c-36bc-5e006f892bf2, HandlerErrorCode: GeneralServiceException)

问题 #

是否可以在同一个CloudFormation模板中同时使用动态扩展与预测扩展？

原模板代码 #

---
Resources:
  myasg:
    Type: AWS::AutoScaling::AutoScalingGroup
    Properties:
      MaxSize: '10'
      MinSize: '2'
      DesiredCapacity: '2'
      VPCZoneIdentifier:
        - subnet1
        - subnet2
      MixedInstancesPolicy:
        InstancesDistribution:
          OnDemandAllocationStrategy: lowest-price
          OnDemandBaseCapacity: 0
          OnDemandPercentageAboveBaseCapacity: 0
          SpotAllocationStrategy: lowest-price
          SpotInstancePools: 2
        LaunchTemplate:
          LaunchTemplateSpecification:
            LaunchTemplateName: mylaunchtemplate
            Version: 1
      Tags:
        - Key: Environment
          Value: Production
          PropagateAtLaunch: true
        - Key: Purpose
          Value: WebServerGroup
          PropagateAtLaunch: false
  scalingpolicy:
    Type: AWS::AutoScaling::ScalingPolicy
    Properties:
      AutoScalingGroupName:
        Ref: myasg
      PolicyType: TargetTrackingScaling
      TargetTrackingConfiguration:
        DisableScaleIn: false
        PredefinedMetricSpecification:
          PredefinedMetricType: ASGAverageCPUUtilization
        TargetValue: 30
      PredictiveScalingConfiguration:
        MaxCapacityBreachBehavior: IncreaseMaxCapacity
        MaxCapacityBuffer: 0
        MetricSpecifications:
          - TargetValue: 30
        Mode: ForecastAndScale

解决方案 #

错误原因 #

你将PredictiveScalingConfiguration直接嵌套在TargetTrackingScaling类型的伸缩策略中，这是AWS不允许的配置方式。预测扩展需要创建独立的、类型为PredictiveScaling的伸缩策略，不能与目标追踪策略合并配置。

可行性说明 #

可以在同一个CloudFormation模板中同时使用动态扩展（如目标追踪）和预测扩展，但必须创建两个独立的伸缩策略：一个负责基于实时指标的动态扩缩容，另一个专门负责基于预测的提前扩缩容。

修改后的模板示例 #

---
Resources:
  myasg:
    Type: AWS::AutoScaling::AutoScalingGroup
    Properties:
      MaxSize: '10'
      MinSize: '2'
      DesiredCapacity: '2'
      VPCZoneIdentifier:
        - subnet1
        - subnet2
      MixedInstancesPolicy:
        InstancesDistribution:
          OnDemandAllocationStrategy: lowest-price
          OnDemandBaseCapacity: 0
          OnDemandPercentageAboveBaseCapacity: 0
          SpotAllocationStrategy: lowest-price
          SpotInstancePools: 2
        LaunchTemplate:
          LaunchTemplateSpecification:
            LaunchTemplateName: mylaunchtemplate
            Version: 1
      Tags:
        - Key: Environment
          Value: Production
          PropagateAtLaunch: true
        - Key: Purpose
          Value: WebServerGroup
          PropagateAtLaunch: false

  # 动态扩展：基于CPU使用率的目标追踪策略
  targetTrackingScalingPolicy:
    Type: AWS::AutoScaling::ScalingPolicy
    Properties:
      AutoScalingGroupName: !Ref myasg
      PolicyType: TargetTrackingScaling
      TargetTrackingConfiguration:
        DisableScaleIn: false
        PredefinedMetricSpecification:
          PredefinedMetricType: ASGAverageCPUUtilization
        TargetValue: 30

  # 预测扩展：独立的预测伸缩策略
  predictiveScalingPolicy:
    Type: AWS::AutoScaling::ScalingPolicy
    Properties:
      AutoScalingGroupName: !Ref myasg
      PolicyType: PredictiveScaling
      PredictiveScalingConfiguration:
        MaxCapacityBreachBehavior: IncreaseMaxCapacity
        MaxCapacityBuffer: 0
        MetricSpecifications:
          - TargetValue: 30
            PredefinedMetricPairSpecification:
              PredefinedMetricType: ASGAverageCPUUtilization
        Mode: ForecastAndScale

关键修改点 #

• 将原有的单一策略拆分为两个独立资源：targetTrackingScalingPolicy（负责动态扩缩容）和predictiveScalingPolicy（负责预测扩缩容）
• 预测扩展策略必须指定PolicyType: PredictiveScaling，并单独配置PredictiveScalingConfiguration
• 两个策略均关联到同一个ASG，实现动态+预测的混合扩缩容逻辑

内容的提问来源于stack exchange，提问作者learner00