GKE ingress modify existing hosts/paths - google-cloud-platform

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