Terraform CDK Python: find VPC Id

Terraform CDK for Terraform
1

Pretty new to CDK for Terraform. I’m using it with Python. I want to create an instance inside a particular VPC.

Code I have now:

 newInstance = Instance(self, 'pythondemo',
        ami="ami-0a02ee601d742e89f",
        instance_type="t2.micro",
        availability_zone="us-east-1a",
        associate_public_ip_address=True,
        tags={"Name": "Python-Demo"},
        user_data = user_data
    )

To be able to create the instance in a particular VPC, I would like to find the VPC id based on the VPC name. I have already imported the VPC module as follows:

from imports.terraform_aws_modules.vpc.aws import TerraformAwsModulesVpcAws

I then also need to find out the subnets within that VPC.

Any idea how to determine the VPC id and subnet ids?

2

You could use the vpc data source with a name filter to find it. I believe the Python type is DataAwsVpc.
From that you could use the subnet ids data source (DataAwsSubnetIds) to look up the subnet ids.

You could use that module to create a vpc in which case you could access its outputs to get the values you need. If you are using in a different stack, you could add as an output to that stack and import via remote state.

3

OK thanks. Will try that.

In the meantime tried some other stuff as well. Follow up question: how then to get the attributes of a VPC that has been created with CDK?

my_vpc =  TerraformAwsModulesVpcAws(self, 
   id='vpc',
   name ="test-vpc",
   cidr = "10.0.0.0/16",
    azs = ["eu-central-1a", "eu-central-1b", "eu-central-1c"],
    public_subnets = ["10.0.101.0/24", "10.0.102.0/24", "10.0.103.0/24"]   
 )


newInstance = Instance(self, 'demo',
    ami="ami-0a02ee601d742e89f",
     instance_type="t2.micro",
     availability_zone="eu-central-1a",
     associate_public_ip_address=True,
     tags={"Name": "Demo"},
     user_data = user_data,
     subnet_id =my_vpc.public_subnets[0]
 )

I want to launch the instance in the newly created VPC.

According to the documentation here or here the public_subnets return a list of ID’s but instead I’m getting back the following:

Error: Error launching source instance: InvalidSubnetID.NotFound: The subnet ID ‘10.0.101.0/24’ does not exist

4

I believe for Python the naming would be my_vpc.public_subnets_output. Unfortunately there is a bug where the type of any output is a string, so you’ll need to add an override to get a single subnet.