Templating via CRS

[bigkevmcd]

I'm wondering if there'd be any interest in providing templating of the resources defined in a CRS.

For example...

apiVersion: addons.cluster.x-k8s.io/v1alpha3
kind: ClusterResourceSet
metadata:
  name: example-crs
  namespace: default
spec:
  clusterSelector:
    matchLabels:
      bootstrap.containers: yes
  resources:
  - kind: ConfigMap
    name: bootstrap-containers

If the resources defined in the bootstrap-containers ConfigMap had something like ${annotations.github-repository} or ${annotations.repository-path} then somewhere around the point where the resources are being applied it could do a replace on the objects.

The fields annotations.X and perhaps labels.X would lookup on the annotations and labels applied to the Cluster object that the CRS applies to and insert those values into the cluster.

This would be useful if you wanted to bootstrap a workload into a newly-provisioned cluster, but customise the processes slightly per-cluster?

[fabriziopandini]

The current stance about addon management is summarized in https://github.com/kubernetes-sigs/cluster-api/blob/main/docs/proposals/20220712-cluster-api-addon-orchestration.md

TL;DR;

• CRS are a very basic solution addon orchestration
• We should rely on tools existing on the ecosystem for more advanced use cases

https://github.com/kubernetes-sigs/cluster-api-addon-provider-helm is an example (but not the only one)