Tag templating

[sylr]

Description

What problem are you trying to solve?

I would like to be able to use go templates to generate dynamic AWS tags for the EC2 instances generated by karpenter, e.g:

---
apiVersion: karpenter.k8s.aws/v1
kind: EC2NodeClass
metadata:
  name: al2023-default
spec:
  # Required, resolves a default ami and userdata
  amiFamily: AL2023
  amiSelectorTerms:
  - alias: al2023@v20241121

  ...

  # Optional, propagates tags to underlying EC2 resources
  tags:
    Name: eks.amazonaws.com/{{ .ClusterName }}/{{ .EC2NodeClassName }}

How important is this feature to you?

Nice to have.

[jonathan-innis]

Can you template this at the level above the NodeClass? I'm curious if rather than us supporting templating directly in our spec, if you can use something like Helm/Kustomize with GitOps to auto-template this out for you so the resultant manifests just have hard data.

In general, I think it's pretty abnormal to see templated values in K8s resources that are directly applied to the cluster.

[sylr]

I do use flux and kustomize to template things but in this case I don't think it would work as what I would really do is to use the NodePool name, e.g.:

  # Optional, propagates tags to underlying EC2 resources
  tags:
    Name: eks.amazonaws.com/{{ .ClusterName }}/{{ .NodePoolName }}

[sftim]

In general, I think it's pretty abnormal to see templated values in K8s resources that are directly applied to the cluster.

When the Kubernetes project does templating, it's usually CEL. But: I agree, doing this at a level above NodePool / node class is the right approach.