[AWS::ElasticLoadBalancingV2::LoadBalancer] - [BUG] - False-positive drift for SubnetMappings

[r-heimann]

Name of the resource

AWS::ElasticLoadBalancingV2::LoadBalancer

Issue Description

When creating a AWS::ElasticLoadBalancingV2::LoadBalancer in eu-central-1 using

      SubnetMappings:
        - SubnetId: !ImportValue VPC1-AZ1Subnet1
        - SubnetId: !ImportValue VPC1-AZ2Subnet1
        - SubnetId: !ImportValue VPC1-AZ3Subnet1

it will cause a drift:

Property	Change	Expected value	Current value
SubnetMappings.0.SubnetId	REMOVE	subnet-XXXXXXX	-
SubnetMappings.1.SubnetId	REMOVE	subnet-XXXXXXX	-
SubnetMappings.2.SubnetId	REMOVE	subnet-XXXXXXX	-

Expected Behavior

Drift is recognizing SubnetMappings.

Observed Behavior

Is it showing up as a false positive drift in CloudFormation.

Test Cases

  NLB:
    Type: AWS::ElasticLoadBalancingV2::LoadBalancer
    Properties:
      Name: "NLB"
      IpAddressType: ipv4
      Scheme: internal
      Type: network
      SubnetMappings:
        - SubnetId: !ImportValue VPC1-AZ1Subnet1
        - SubnetId: !ImportValue VPC1-AZ2Subnet1
        - SubnetId: !ImportValue VPC1-AZ3Subnet1

Other Details

May be related to #458

[greg5123334]

Confirmed.

        elb = elbv2.CfnLoadBalancer(self, "MyCfnLoadBalancer",
                                    ip_address_type="ipv4",
                                    name="NLB",
                                    scheme="internal",
                                    subnet_mappings=[elbv2.CfnLoadBalancer.SubnetMappingProperty(
                                        subnet_id=vpc.private_subnets[0].subnet_id,
                                    ), elbv2.CfnLoadBalancer.SubnetMappingProperty(
                                        subnet_id=vpc.private_subnets[1].subnet_id,
                                    )],
                                    type="network"
                                    )

Expected:

{
  "IpAddressType": "ipv4",
  "Name": "NLB",
  "Scheme": "internal",
  "SubnetMappings": [
    {
      "SubnetId": "subnet-xxxxxxxx"
    }
  ],
  "Type": "network"
}

Actual:

{
  "IpAddressType": "ipv4",
  "Name": "NLB",
  "Scheme": "internal",
  "SubnetMappings": [
    {}
  ],
  "Type": "network"
}

[FarrOut]

Just retested. Issue partially persists. False-positive drift remains, but only in some regions.

Some that I have tested:

• eu-central-1 (FRA) - Good
• eu-west-1 (DUB) - Bad
• ap-southeast-2 (SYD) - Bad
• us-east-1 (IAD) - Bad

        elb = elbv2.CfnLoadBalancer(self, "MyCfnLoadBalancer",
                                    ip_address_type="ipv4",
                                    name="NLB",
                                    scheme="internal",
                                    subnet_mappings=[elbv2.CfnLoadBalancer.SubnetMappingProperty(
                                        subnet_id=vpc.private_subnets[0].subnet_id,
                                    ), elbv2.CfnLoadBalancer.SubnetMappingProperty(
                                        subnet_id=vpc.private_subnets[1].subnet_id,
                                    )],
                                    type="network"
                                    )

Expected

{
  "IpAddressType": "ipv4",
  "Name": "NLB",
  "Scheme": "internal",
  "SubnetMappings": [
    {
      "SubnetId": "subnet-xxxxxxxx"
    },
    {
      "SubnetId": "subnet-xxxxxxxxxx"
    }
  ],
  "Type": "network"
}

Actual

{
  "IpAddressType": "ipv4",
  "Name": "NLB",
  "Scheme": "internal",
  "SubnetMappings": [
    {},
    {}
  ],
  "Type": "network"
}

[r-heimann]

I can confirm that the issue is fixed in eu-central-1