Kustomize Patch Ingress Issue - Go construct

Question

I am new to kustomize and trying to figure out how to patch my ingress that is running via OpenShift Container Platform.

The base config works fine and the overlay was working until I introduced my ingress overlay patch. For reference the patch-service overlay does work so I am pretty sure my structure and links are all good, however the error I get on my project when syncronising to OpenShift (via ArgoCD) is:

one or more objects failed to apply, reason: Ingress in version "v1" cannot be handled as a Ingress: json: cannot unmarshal number into Go struct field IngressServiceBackend.spec.defaultBackend.service.port of type v1.ServiceBackendPort (retried 5 times).

Application Repo Structure

|mssql-example
├── base
│   ├── deployment.yaml
│   ├── ingress.yaml
│   ├── kustomization.yaml
│   ├── storage.yaml
│   └── service.yaml
└── overlays
    ├── nprd-dev
    │   ├── **patch-ingress.yaml**
    │   ├── patch-service.yaml
    │   └── kustomization.yaml
    ├── nprd-sit
    │   ├── patch-ingress.yaml
    │   ├── patch-service.yaml
    │   └── kustomization.yaml
    └── nprd-uat
    │   ├── patch-ingress.yaml
    │   ├── patch-service.yaml
    │   └── kustomization.yaml

mssql-example\base\ingress.yaml

---
kind: Ingress
apiVersion: networking.k8s.io/v1
metadata:
  name: mssql-example-adc
  annotations:
    ingress.citrix.com/frontend-ip: 192.168.1.10
    ingress.citrix.com/insecure-port: '1433'
    ingress.citrix.com/insecure-service-type: tcp
    kubernetes.io/ingress.class: citrix-vpx
spec:
  defaultBackend:
    service:
      name: mssql-service
      port:
        number: 31433

mssql-example\overlays\nprd-dev\kustomization.yaml

---
apiVersion: kustomize.config.k8s.io/v1beta1
kind: Kustomization
namespace: ops-example-dev
resources:
  - ../../base
patches:
  - path: patch-ingress.yaml
    target:
      kind: Ingress
      version: v1
      name: mssql-example-adc
  - path: patch-service.yaml
    target:
      kind: Service
      version: v1
      name: mssql-example-tcp

mssql-example\overlays\nprd-dev\patch-ingress.yaml

---
- op: replace
  path: /metadata/name
  value: mssql-example-ingress-dev
- op: replace
  path: /spec/defaultBackend/service/port
  value: 31434

I think my path may be wrong, but I can't seem to work out how to correctly identify the replacement path for the spec when it is defaultBackend. I tried the path as /spec/defaultBackend/0/service/port and /spec/0/defaultBackend/service/port incase it was an array.

Answer 1

The error is telling you everything you need to know:

cannot unmarshal number into Go struct field

First, look at the format of your initial Ingress manifest:

kind: Ingress
apiVersion: networking.k8s.io/v1
metadata:
  name: mssql-example-adc
  annotations:
    ingress.citrix.com/frontend-ip: 192.168.1.10
    ingress.citrix.com/insecure-port: '1433'
    ingress.citrix.com/insecure-service-type: tcp
    kubernetes.io/ingress.class: citrix-vpx
spec:
  defaultBackend:
    service:
      name: mssql-service
      port:
        number: 31433

Pay particular attention to the structure of spec.defaultBackend.service.port.

Now, look at the output generated by your patch:

$ kustomize build
apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  annotations:
    ingress.citrix.com/frontend-ip: 192.168.1.10
    ingress.citrix.com/insecure-port: "1433"
    ingress.citrix.com/insecure-service-type: tcp
    kubernetes.io/ingress.class: citrix-vpx
  name: mssql-example-ingress-dev
spec:
  defaultBackend:
    service:
      name: mssql-service
      port: 31434

Do you see the difference? You've replaced a structured value:

port:
  number: 31433

With an integer:

port: 31434

Just update your patch to target ...service/port/number instead:

apiVersion: kustomize.config.k8s.io/v1beta1
kind: Kustomization
resources:
- ingress.yaml

patches:
  - target:
      name: mssql-example-adc
    patch: |
      - op: replace
        path: /metadata/name
        value: mssql-example-ingress-dev
      - op: replace
        path: /spec/defaultBackend/service/port/number
        value: 31434

Which results in:

apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  annotations:
    ingress.citrix.com/frontend-ip: 192.168.1.10
    ingress.citrix.com/insecure-port: "1433"
    ingress.citrix.com/insecure-service-type: tcp
    kubernetes.io/ingress.class: citrix-vpx
  name: mssql-example-ingress-dev
spec:
  defaultBackend:
    service:
      name: mssql-service
      port:
        number: 31434