What does 'validation: client' in a kustomization mean?

[xeruf]

I see this property mentioned all over the place but could not find any explanation to it in the docs or anywhere else

[stefanprodan]

I doubt there is any mention of this field in latest docs, this opinion was removed some years ago from Flux APIs. Flux now uses Kubernetes server-side apply, which means manifests are always validated by the Kubernetes OpenAPI before being being persisted in etcd.

[mkadricogito]

@stefanprodan I recently encountered an issue when trying to update from 0.41.2 to v2.0.0-rc.1

Warning  ReconciliationFailed     5m5s (x2 over 5m15s)  kustomize-controller  Kustomization/flux-system/cert-manager dry-run failed, error: failed to p │
│ rune fields: failed add back owned items: failed to convert merged object at version kustomize.toolkit.fluxcd.io/v1: .spec.validation: field not declared │
│  in schema

it turns out that our existing kustomization has this flag set to

---
apiVersion: kustomize.toolkit.fluxcd.io/v1beta2
kind: Kustomization
metadata:
  name: podinfo
  namespace: default
spec:
  interval: 1m0s
  path: ./kustomize
  prune: false
  sourceRef:
    kind: GitRepository
    name: podinfo
    namespace: flux-system
  targetNamespace: default
  validation: client

i.e it breaks the flux-system kustomization, so its not reverse compatible I see,
any way to overcome or get around it

[kingdonb]

@mkadricogito The flag you have there hasn't been effective since about Flux v0.18, see this reference in 2021 where the field was removed:

https://fluxcd.io/blog/2021/09/server-side-reconciliation-is-coming/

You can remove the field from your manifests, since it's ineffective and was deprecated with v1beta2 Flux Kustomization, it will not change anything except removing the error message that's preventing you from moving forward.

Edit: more specific link to the "What you should do" and what effect it has part:
https://fluxcd.io/blog/2021/09/server-side-reconciliation-is-coming/#:~:text=Change%20in%20the,you%20should%20do

Server-side validation is now assumed. Remove this field from .spec.