VPC:expicit passing availability zones produces errors

[gratinierer]

Describe the bug

creating a VPC with subnets and passing the availabilty-zones explicit, fails when calling SubnetSelection

        self.vpc_config.subnet_private_interface_endpoints = aws_ec2.SubnetConfiguration(
            name='interface-endpoints',
            subnet_type=aws_ec2.SubnetType.PRIVATE_ISOLATED,
            cidr_mask=20)
        self.vpc_config.vpc_general = aws_ec2.Vpc(self, 'GeneralVpc',
                                                  vpc_name='vpc',
                                                  create_internet_gateway=True,
                                                  default_instance_tenancy=aws_ec2.DefaultInstanceTenancy.DEFAULT,
                                                  enable_dns_hostnames=True,
                                                  enable_dns_support=True,
                                                  flow_logs=None,
                                                  gateway_endpoints=None,
                                                  ip_addresses=aws_ec2.IpAddresses.cidr(self.ip_range_vpc),
                                                  ip_protocol=aws_ec2.IpProtocol.IPV4_ONLY,
                                                  availability_zones=[
                                                      'eu-west-1a',
                                                      'eu-west-1b'],
                                                  nat_gateway_provider=aws_ec2.NatProvider.gateway(),
                                                  nat_gateways=2,
                                                  subnet_configuration=[
                                                      self.vpc_config.subnet_private_interface_endpoints,
                                                  ],
                                                  restrict_default_security_group=True,
                                                  )
        aws_ec2.SubnetSelection(
            subnet_group_name=self.vpc_config.subnet_private_interface_endpoints.name)

Regression Issue

• Select this option if this issue appears to be a regression.

Last Known Working CDK Version

No response

Expected Behavior

The code should work as it des with

max_azs=2

Current Behavior

RuntimeError: Error: There are no subnet groups with name '....' in this VPC. Available names:

Reproduction Steps

see code above

Possible Solution

No response

Additional Information/Context

No response

CDK CLI Version

2.176.0 (build 899965d)

Framework Version

No response

Node.js Version

20.15.0

OS

win

Language

Python

Language Version

No response

Other information

No response

[pahud]

aws_ec2.SubnetSelection(
            subnet_group_name=self.vpc_config.subnet_private_interface_endpoints.name)

what's happening here is that CDK would invoke SDK calls to find out that subnet_group_name, which I can't see the value, and it can't find that.

Please check:

RuntimeError: Error: There are no subnet groups with name '....' in this VPC. Available names:

1. Are the Available names: in your specified VPC? If no, you might specify incorrect VPC. If yes, the VPC is correct defined and we'll need to find out why the SDK can't find the subnet_group_name
2. You might want to use npx cdk diff -vv (double v) to view what's happening behind the scene. This would help you find out the root cause with more detailed debugging log.

[gratinierer]

Hi pahud,
As noted: my complete stack(with 10 subnets and many other Stacks) works fine with „maxAz=2“. If i switch to explicit Az-definition „SubnetSelection“ fails for every subnet with the error.
„AvailableNames:“ are completely empty in this cases.

[gratinierer]

Sorry, error was on my side. The availybilty-zone was empty for some configuration reason, what produced this effect.
Thanks for your patient reaction!

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