Kustomize how to replace only the host in Ingress configuration

Question

I've got this ingress.yaml base configuration:

apiVersion: extensions/v1beta1
kind: Ingress
metadata:
  labels:
    sia: aza
    app: asap-ingress-internal
  name: asap-ingress-internal
  annotations:
    kubernetes.io/ingress.class: "nginx-external"
    nginx.ingress.kubernetes.io/use-regex: "true"
spec:
  rules:
    - host: the-host-value
      http:
        paths:
          - path: /asap-srv-template/(.*)
            backend:
              serviceName: asap-srv-template
              servicePort: 8080

And want to replace the spoec.rules.host value only (and keep all http.paths as is.

So I create a env-var.yaml like this:

apiVersion: extensions/v1beta1
kind: Ingress
metadata:
  name: asap-ingress-internal
spec:
  rules:
    - host: the.real.hostname

But the result is the following:

$ kustomize build
apiVersion: extensions/v1beta1
kind: Ingress
metadata:
  annotations:
    kubernetes.io/ingress.class: nginx-external
    nginx.ingress.kubernetes.io/use-regex: "true"
  labels:
    app: asap-ingress-internal
    env: dev
    sia: aza
  name: asap-ingress-internal
  namespace: aza-72461-dev
spec:
  rules:
  - host: the.real.hostname

I have lost all http.paths configuration and I can't find out how to do.

I tried with patches: or patchesStrategicMerge in kustomization.yaml but the result is always the same.

Any help would be greatly appreciated

Answer 1

You can use a json patch for this, below is an example.

Here is an example kustomization.yaml . It will call out a patch in the patches section:

apiVersion: kustomize.config.k8s.io/v1beta1
kind: Kustomization

resources:
- ../../base/app1

patches:
- target:
    kind: Ingress
    name: my-ingress
  path: ingress-patch.json  

Here would be an example ingress-patch.json :

[
    { 
        "op": "replace", 
        "path": "/spec/rules/0/host", 
        "value": "the.real.hostname"
    }
]

Answer 2

Another option is to do inline patch. It's the same approach mroma offered, but without the file. I find it simpler.

# kustomization.yaml

resources:
  - ingress.yaml
patches:
  - target:
      kind: Ingress
      name: asap-ingress-internal
    patch: |-
      - op: replace
        path: /spec/rules/0/host
        value: the.real.hostname

Answer 3

If you are on a recent version of kubernetes (I think starting form 18) the Ingres api version is no longer the beta one apiVersion: extensions/v1beta1 it is now apiVersion: networking.k8s.io/v1 .

I have tested bellow sample and it works:

ingress.yaml

apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: asap-ingress-internal
  annotations:
    kubernetes.io/ingress.class: "nginx-external"
    nginx.ingress.kubernetes.io/use-regex: "true"
spec:
  rules:
    - host: the-host-value
      http:
        paths:
          - path: /asap-srv-template/(.*)
            backend:
              serviceName: asap-srv-template
              servicePort: 8080

ingress-patch.yaml

apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: asap-ingress-internal
spec:
  rules:
    - host: the.real.hostname

kustomization.yaml

resources:
- ingress.yaml
patchesStrategicMerge:
- ingress-patch.yaml

Tested with both kubectl kustomize (version of kubectl is v1.19.7 ) and kustomize build (version of standalone kustomize is v3.5.4 )