Helm_Lab_08 | SubCharts

Helm_Lab_08

Purpose

The Purpose of this lab is to give the understanding SubCharts (sometimes called a partial or a subtemplate).

To get going, let's take a quick look at SubChartsTemplate

To this point we have been working only with one chart. But charts can have dependencies, called subcharts, that also have their own values and templates

In this section we will see Sharing Templates with Subcharts.

Parent charts and subcharts can share templates. Any defined block in any chart is available to other charts.

For example, we can define a simple template like this:

{{- define "labels" }}from: mychart{{ end }}

Thus, the labels chart can be included from any other chart.

While chart developers have a choice between include and template, one advantage of using include is that include can dynamically reference templates:

{{ include $mytemplate }}

01

Using template function in helm

• Update the gowebapp/templates/deployment.yaml

{{- define "gowebappchart.labels" }}
app.kubernetes.io/name: app
app.kubernetes.io/instance: goweb-app
{{- end }}
apiVersion: apps/v1
kind: Deployment
metadata:
  name: goweb-app
  labels:
{{- template "gowebappchart.labels" }}
spec:
  replicas: 1
  selector:
    matchLabels:
      app.kubernetes.io/name: app
      app.kubernetes.io/instance: goweb-app
  template:
    metadata:
      labels:
        app.kubernetes.io/name: app
        app.kubernetes.io/instance: goweb-app
    spec:
      containers:
        - name: {{ .Values.containers.name }}
          image: "{{ .Values.containers.image }}:{{ .Values.containers.tag }}"
          imagePullPolicy: IfNotPresent
          ports:
          - name: http
            containerPort: 8080
            protocol: TCP
          env:
{{- range $key, $value := .Values.containers.envVar }}
          - name: {{ $key }}
            value: {{ $value | quote }}
{{- end }}
{{- if .Values.containers.livenessProbe }}
          livenessProbe:
      {{- with .Values.containers.livenessProbe }}
        {{- toYaml . | nindent 12 }}
      {{- end }}
{{- end }}
{{- if .Values.containers.readinessProbe }}
          readinessProbe:
      {{- with .Values.containers.readinessProbe }}
        {{- toYaml . | nindent 12 }}
      {{- end }}
{{- end }}

So you can validate the output by:-

helm template goweb-app ./gowebapp

02

Using include function in helm

• Update the gowebapp/templates/deployment.yaml

{{- define "gowebappchart.labels" }}
app.kubernetes.io/name: app
app.kubernetes.io/instance: goweb-app
{{- end }}
apiVersion: apps/v1
kind: Deployment
metadata:
  name: goweb-app
  labels:
{{- include "gowebappchart.labels" . | nindent 4 }}
spec:
  replicas: 1
  selector:
    matchLabels:
      app.kubernetes.io/name: app
      app.kubernetes.io/instance: goweb-app
  template:
    metadata:
      labels:
        app.kubernetes.io/name: app
        app.kubernetes.io/instance: goweb-app
    spec:
      containers:
        - name: {{ .Values.containers.name }}
          image: "{{ .Values.containers.image }}:{{ .Values.containers.tag }}"
          imagePullPolicy: IfNotPresent
          ports:
          - name: http
            containerPort: 8080
            protocol: TCP
          env:
{{- range $key, $value := .Values.containers.envVar }}
          - name: {{ $key }}
            value: {{ $value | quote }}
{{- end }}
{{- if .Values.containers.livenessProbe }}
          livenessProbe:
      {{- with .Values.containers.livenessProbe }}
        {{- toYaml . | nindent 12 }}
      {{- end }}
{{- end }}
{{- if .Values.containers.readinessProbe }}
          readinessProbe:
      {{- with .Values.containers.readinessProbe }}
        {{- toYaml . | nindent 12 }}
      {{- end }}
{{- end }}

So you can validate the output by:-

helm template goweb-app ./gowebapp