how to list all the NAT Gateway in a VPC via CDK?

Question

In CDK, i see that NAT gateways are represented as CfnNatGateway. I am just whether there is any way to list all the CfnNatGateway.

My purpose is to whitelist the elastic ips of those NAT gateways through CDK.

Answer 1

You could use a Custom Resource, which perform "arbitrary lookups or modifications during a CloudFormation deployment." A Custom Resource is in essence a Lambda that is called during the stack deployments, which you would use to call DescribeNatGateway API, extract the IPs and output the result.

Whether you should do this is a different question. Using a Custom Resource to lookup IPs introduces deploy-time side-effects. Instead, the CDK best practice is deterministic deploys:

Determinism is key to successful AWS CDK deployments. A AWS CDK app should have essentially the same result whenever it is deployed to a given environment.

The CDK would have you lookup the IPs at synth-time:

Since your AWS CDK app is written in a general-purpose programming language, it can execute arbitrary code, use arbitrary libraries, and make arbitrary network calls. For example, you could use an AWS SDK to retrieve some information from your AWS account while synthesizing your app...