Cannot add AutoScalingGroup to more than one Target Group

When attempting to assign an ASG to multiple target groups, CDK errors out with Cannot add AutoScalingGroup to 2nd Target Group

CFN supports passing in a list of Target Group ARNs to an autoscaling group - https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-properties-as-group.html#cfn-as-group-targetgrouparns

Use Case

This feature is necessary if anybody would like to assign multiple load balancers to an ASG

Proposed Solution

Remove the check here - https://github.com/aws/aws-cdk/blob/master/packages/%40aws-cdk/aws-autoscaling/lib/auto-scaling-group.ts#L559

Figure out any other functions that are effected and come up with workarounds. Rico thinks there could be issues with scaleOnRequestCount()

Other

• 👋 I may be able to implement this feature request
• ⚠️ This feature might incur a breaking change

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This is a 🚀 Feature Request

[manikandanmsairam]

+1 We have a usecase where the application has to be exposed both internally and to Internet. Internet facing load balancer will be restricted to CloudFront IPs and internal load balancer will be accessed by another application for flushing. Hence we need to attach the same target group into internal load balancer and internet facing load balancer.

[kevinslin]

current workaround we are using

...
const cfnAsg = asg.node.defaultChild as CfnAutoScalingGroup;
cfnAsg.targetGroupArns = [tgHTTP.targetGroupArn, tgHTTPS.targetGroupArn];