How to generate generic templates

[amoscatelli]

Hi everybody,
is it possible to generate a generic template/helm chart by using k8s:resources goal ?

For example by using "helm create" something similar is created for ingress :

{{- if .Values.ingress.enabled -}}
{{- $fullName := include "chart.fullname" . -}}
{{- $svcPort := .Values.service.port -}}
{{- if and .Values.ingress.className (not (semverCompare ">=1.18-0" .Capabilities.KubeVersion.GitVersion)) }}
  {{- if not (hasKey .Values.ingress.annotations "kubernetes.io/ingress.class") }}
  {{- $_ := set .Values.ingress.annotations "kubernetes.io/ingress.class" .Values.ingress.className}}
  {{- end }}
{{- end }}
{{- if semverCompare ">=1.19-0" .Capabilities.KubeVersion.GitVersion -}}
apiVersion: networking.k8s.io/v1
{{- else 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 "chart.labels" . | nindent 4 }}
  {{- with .Values.ingress.annotations }}
  annotations:
    {{- toYaml . | nindent 4 }}
  {{- end }}
spec:
  {{- if and .Values.ingress.className (semverCompare ">=1.18-0" .Capabilities.KubeVersion.GitVersion) }}
  ingressClassName: {{ .Values.ingress.className }}
  {{- end }}
  {{- if .Values.ingress.tls }}
  tls:
    {{- range .Values.ingress.tls }}
    - hosts:
        {{- range .hosts }}
        - {{ . | quote }}
        {{- end }}
      secretName: {{ .secretName }}
    {{- end }}
  {{- end }}
  rules:
    {{- range .Values.ingress.hosts }}
    - host: {{ .host | quote }}
      http:
        paths:
          {{- range .paths }}
          - path: {{ .path }}
            {{- if and .pathType (semverCompare ">=1.18-0" $.Capabilities.KubeVersion.GitVersion) }}
            pathType: {{ .pathType }}
            {{- end }}
            backend:
              {{- if semverCompare ">=1.19-0" $.Capabilities.KubeVersion.GitVersion }}
              service:
                name: {{ $fullName }}
                port:
                  number: {{ $svcPort }}
              {{- else }}
              serviceName: {{ $fullName }}
              servicePort: {{ $svcPort }}
              {{- end }}
          {{- end }}
    {{- end }}
{{- end }}

So this is almost completely driven by values.yaml.
By using the k8s:resources goal can I achieve something similar ?

I don't want to specify such details during the maven compilation, I want to specify things like hostnames or tsl secret name later.

Thank you in advance

[manusa]

Not with such a complicated template (if statements, etc.).

However you can achieve a certain level of complexity by combining values and go templates, see the spring-boot-helm quickstart for details.

There's also this presentation from EclipseCon 2023 which describes how JKube works (at the moment) regarding Helm: https://www.youtube.com/watch?v=DvMickoLlXM

Notice the difference between the inner and outer loop cycles.

k8s:resource for inner loop needs to be able to generate valid YAML files that can be applied directly to the cluster

k8s:resource + k8s:helm for the outer loop needs to be able to generate the Helm templates with the appropriate template content.

This brings in a set of challenges that we're still trying to overcome.
See for example:

• Allow Helm in Yaml fragments #2689
• https://github.com/eclipse/jkube/issues?q=is%3Aopen+is%3Aissue+label%3A%22component%2Fhelm+%E2%8E%88%22

[amoscatelli]

Thank you for your answer.
Is it possible to achieve the same without making any changes to pom.xml ?

What I don't like is to specificy every substitution inside pom.xml :
https://github.com/eclipse/jkube/blob/master/quickstarts/maven/spring-boot-helm/pom.xml

I tried to use helm variables directly but I got a :
"spec.replicas: string found, integer expected, violation type=type"

[manusa]

You could use a template file for that: https://github.com/eclipse-jkube/jkube/blob/729dc8a0e201499b7fde995d7e61a7de8da110ae/quickstarts/maven/spring-boot-helm/src/main/jkube/template.yaml

However, the recommended approach is to use pom.xml instead.

Check the quickstart to see how some of this variables defined as template parameters are used in this example (for example the deployment's resource limits).