aws-eks: Support CUSTOM AMI type on Nodegroups

[Artemigos]

Describe the feature

CloudFormation supports passing CUSTOM as value for AmiType: https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-resource-eks-nodegroup.html#cfn-eks-nodegroup-amitype

This is not available in CDK, making the use of custom AMIs impossible.

Use Case

When building custom AMIs for a cluster (e.g. based on the EKS optimized images) you should be able to use them.

Proposed Solution

Rough idea:

• add the CUSTOM type to the enum:

  aws-cdk/packages/aws-cdk-lib/aws-eks/lib/managed-nodegroup.ts

  Line 29 in 3b95777

  export enum NodegroupAmiType {

• modify

  aws-cdk/packages/aws-cdk-lib/aws-eks/lib/managed-nodegroup.ts

  Line 635 in 3b95777

  function getPossibleAmiTypes(instanceTypes: InstanceType[]): NodegroupAmiType[] {

  to append CUSTOM as the last option for all architectures

It looks like this should already be enough, but I didn't actually attempt doing this.

Other Information

I tried forcing the issue by bypassing TypeScript checks: amiType: ('CUSTOM' as any) - internal check rejected it. After investigating a little - the Nodegroup constructor tries to do the right thing and validates the value, but completely ignores the existence of CUSTOM in CloudFormation.

Acknowledgements

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

CDK version used

2.133.0

Environment details (OS name and version, etc.)

Ubuntu 22.04.4 LTS

[pahud]

@Artemigos Yes we should support that.

1. when CUSTOM is provided, a launch template has to be provided as well.
2. we probably should add CUSTOM to possibleAmiTypes here:

aws-cdk/packages/aws-cdk-lib/aws-eks/lib/managed-nodegroup.ts

Line 429 in 3b95777

possibleAmiTypes = getPossibleAmiTypes(instanceTypes);

Feel free to submit a PR for it. Thank you.