DRY Gateway with domain transformation

[sebiklamar]

No description provided.

[sebiklamar]

Issue

Kustomize's transformers do not work with Gateway and Certificate because transformer code cannot cope with *.FQDN naming and with short domain (example.com instead of foo.example.comwith 1 domain component instead of 2 in addition to TLD). For the *.FQDN one could change the indices. For the latter (short FQDN) maybe do an additional split iteration.
Needless to say: no domain prefix transformation.

Source...

# base/gw-external.yaml
apiVersion: gateway.networking.k8s.io/v1
kind: Gateway
metadata:
  name: external
  namespace: gateway
spec:
  listeners:
    - hostname: "*.example.com"
...
    - hostname: example.com
...

... becomes in the overlay:

apiVersion: gateway.networking.k8s.io/v1
kind: Gateway
metadata:
  name: dev-external
  namespace: gateway
spec:
  listeners:
  - hostname: '*.dev.iseja.net'
...   
  - hostname: example.dev.iseja.net

Transformer Code

Using the f. transformer code:

gateway-replace-hostname.yaml

# k8s/_transformers/replace-domain/repl/gateway-replace-hostname.yaml
- source:
    kind: ConfigMap
    name: cluster-param
    fieldPath: data.DOMAIN_TLD
  targets:
    - select:
        kind: Gateway
      fieldPaths:
        - spec.listeners.*.hostname
      options:
        delimiter: "."
        index: 2
- source:
    kind: ConfigMap
    name: cluster-param
    fieldPath: data.DOMAIN_BASE
  targets:
    - select:
        kind: Gateway
      fieldPaths:
        - spec.listeners.*.hostname
      options:
        delimiter: "."
        index: 1

certificate-replace-dnsNames.yaml

# k8s/_transformers/replace-domain/repl/certificate-replace-dnsNames.yaml
- source:
    kind: ConfigMap
    name: cluster-param
    fieldPath: data.DOMAIN_TLD
  targets:
    - select:
        kind: Certificate
      fieldPaths:
        - spec.dnsNames.*
      options:
        delimiter: "."
        index: 2
- source:
    kind: ConfigMap
    name: cluster-param
    fieldPath: data.DOMAIN_BASE
  targets:
    - select:
        kind: Certificate
      fieldPaths:
        - spec.dnsNames.*
      options:
        delimiter: "."
        index: 1