GKE ingress modify existing hosts/paths

Question

Is it possible to modify (add/remove) existing hosts from command line/ by a script? I want to add new applications dynamically when they are deployed for the first time. I currently ended up with this script:

#!/bin/bash

APP_NAME=$1

if [[ -z $(kubectl get ingress ingress-gw -o yaml | grep "serviceName: $APP_NAME-service") ]]
then echo "$(kubectl get ingress ingress-gw -o yaml | sed '/^status:$/Q')
  - host: $APP_NAME.example.com
    http:
      paths:
      - path: "/*"
        backend:
          serviceName: $APP_NAME-service
          servicePort: 80
$(kubectl get ingress ingress -o yaml | sed -n -e '/^status:$/,$p')" | kubectl apply -f -
fi

In nutshell it downloads the existing ingress configuration, checks if the app is defined and if not it is injected to the end of the file, just before the status: entry and the config is re-applied. It is rather a hack than a nice solution.

I m wondering if I can either configure the ingress to load the hosts and paths dynamically based on some annotations on the services in the same project or if I can at least call some command to add or remove a host.

Answer 1

You can download the configuration in JSON format and using the kubectl patch COMMAND it's possible to update the objects. So you can put all of that in a script to update a ingress dynamically. For more information please follow the above mentioned link.

Example: kubectl get ing mying -o json

Answer 2

I am not sure what your requirements are, but I guess usually such stuff would be done with Helm. You can define an ingress with templates and specify values.yaml which could provide the values necessary to generate that file. A slight adaption of a helm chart generated with helm create

{{- if .Values.ingress.enabled -}}
{{- $fullName := include "ingresstest.fullname" . -}}
{{- $svcPort := .Values.service.port -}}
{{- if semverCompare ">=1.14-0" .Capabilities.KubeVersion.GitVersion -}}
apiVersion: networking.k8s.io/v1beta1
{{- else -}}
apiVersion: extensions/v1beta1
{{- end }}
kind: Ingress
metadata:
  name: {{ $fullName }}
  labels:
    {{- include "ingresstest.labels" . | nindent 4 }}
  {{- with .Values.ingress.annotations }}
  annotations:
    {{- toYaml . | nindent 4 }}
  {{- end }}
spec:
  {{- if .Values.ingress.tls }}
  tls:
    {{- range .Values.ingress.tls }}
    - hosts:
        {{- range .hosts }}
        - {{ . | quote }}
        {{- end }}
      secretName: {{ .secretName }}
    {{- end }}
  {{- end }}
  rules:
    {{-   range $host := .Values.ingress.hosts }} 
    - host: {{ $host.host | quote }}
      http:
        paths:
          {{- range .paths }}
          - path: {{ . }}
            backend:
              serviceName: {{ $host.service }}
              servicePort: {{ $svcPort }}
          {{- end }}
    {{- end }}
  {{- end }}

and values.yaml (snippet)

ingress:
  enabled: true
  annotations: {}
    # kubernetes.io/ingress.class: nginx
    # kubernetes.io/tls-acme: "true"
  hosts:
    - host: foo.example.com
      service: foo-service
      paths:
        - "/*"
    - host: bar.example.com
      service: bar-service
      paths:
     - "/*"

gives a similar result:

apiVersion: networking.k8s.io/v1beta1
kind: Ingress
metadata:
  name: RELEASE-NAME-ingresstest
  labels:
    helm.sh/chart: ingresstest-0.1.0
    app.kubernetes.io/name: ingresstest
    app.kubernetes.io/instance: RELEASE-NAME
    app.kubernetes.io/version: "1.16.0"
    app.kubernetes.io/managed-by: Helm
spec:
  rules: 
    - host: "foo.example.com"
      http:
        paths:
          - path: /*
            backend:
              serviceName: foo-service
              servicePort: 80

    - host: "bar.example.com"
      http:
        paths:
          - path: /*
            backend:
              serviceName: bar-service
              servicePort: 80