How to Fix CloudFormation error "Provided Load Balancers may not be valid. Please ensure they exist and try again

Question

when I try to create Autoscale group with Application load balancer with the following cloudformation yml file

    LoadBalancer: 
      Type: AWS::ElasticLoadBalancingV2::LoadBalancer
      Properties: 
        Type: application
        Subnets: 
          Ref: VPCZoneIdentifier  

    AutoScalingGroup:
      Type: AWS::AutoScaling::AutoScalingGroup
      DependsOn: LoadBalancer
      Properties:
        AvailabilityZones: 
          Ref: "AvailabilityZones"
        Cooldown: 120
        DesiredCapacity:
          Ref: DesiredCapacityASG
        LaunchConfigurationName: 
          Ref: LaunchConfiguration
        MaxSize:
          Ref: MaxSizeASG
        MinSize:
          Ref: MinSizeASG
        LoadBalancerNames: 
          - Ref: "LoadBalancer"
        TargetGroupARNs:
          - !Ref TargetGroup

I got an error saying "Provided Load Balancers may not be valid. Please ensure they exist and try again. (Service: AmazonAutoScaling; Status Code: 400; Error Code: ValidationError; Request ID:)"

Answer 1

this error is happening because you used LoadBalancerNames for Application loadbalancer as it is noted here

to fix it : remove the LoadBalancerNames and keep TargetGroupARNs in the properties

LoadBalancerNames:
- Ref: "LoadBalancer"

so the yml file will be like :

    AutoScalingGroup:
      Type: AWS::AutoScaling::AutoScalingGroup
      DependsOn: LoadBalancer
      Properties:
        AvailabilityZones: 
          Ref: "AvailabilityZones"
        Cooldown: 120
        DesiredCapacity:
          Ref: DesiredCapacityASG
        LaunchConfigurationName: 
          Ref: LaunchConfiguration
        MaxSize:
          Ref: MaxSizeASG
        MinSize:
          Ref: MinSizeASG
        TargetGroupARNs:
          - !Ref TargetGroup