Session 2: Creating and Hosting Custom Helm Charts

🎯 Session 2: Creating and Hosting Custom Helm Charts

In this session, you’ll learn to:

✅ Create your own Helm charts from scratch
✅ Customize templates and use values effectively
✅ Understand and use _helpers.tpl
✅ Host charts on GitHub as a Helm repository
✅ Apply real-world scenarios (Ingress, ConfigMap, HPA)

🛠️ Step 1: Create a Custom Chart

helm create nginx-demo
cd nginx-demo

This creates the following structure:

nginx-demo/
├── charts/
├── Chart.yaml
├── templates/
│   ├── deployment.yaml
│   ├── _helpers.tpl
│   ├── hpa.yaml
│   ├── ingress.yaml
│   ├── service.yaml
│   ├── configmap.yaml
│   └── tests/
└── values.yaml

📄 What is `_helpers.tpl`?

_helpers.tpl is a special file used to define reusable template snippets using Go’s template syntax. It’s where you can define helper functions like naming conventions or labels, which you can include in other templates using {{ include "name" . }}.

✅ Example: `_helpers.tpl`

{{- define "nginx-demo.name" -}}
nginx
{{- end }}

{{- define "nginx-demo.fullname" -}}
{{ .Release.Name }}-nginx
{{- end }}

{{- define "nginx-demo.labels" -}}
app.kubernetes.io/name: {{ include "nginx-demo.name" . }}
helm.sh/chart: {{ .Chart.Name }}-{{ .Chart.Version }}
app.kubernetes.io/instance: {{ .Release.Name }}
app.kubernetes.io/managed-by: {{ .Release.Service }}
{{- end }}

{{- define "nginx-demo.serviceAccountName" -}}
{{- if .Values.serviceAccount.name }}
{{ .Values.serviceAccount.name }}
{{- else }}
{{ include "nginx-demo.fullname" . }}
{{- end }}
{{- end }}

📌 Usage in Other Templates

metadata:
  name: {{ include "nginx-demo.fullname" . }}
  labels:
    {{- include "nginx-demo.labels" . | nindent 4 }}

This avoids duplication and keeps your chart DRY (Don’t Repeat Yourself).

📦 Custom `values.yaml`

replicaCount: 2

image:
  repository: nginx
  pullPolicy: IfNotPresent
  tag: "1.25.2"

service:
  type: ClusterIP
  port: 80

ingress:
  enabled: true
  className: "nginx"
  annotations:
    nginx.ingress.kubernetes.io/rewrite-target: /
  hosts:
    - host: nginx.local
      paths:
        - path: /
          pathType: Prefix

config:
  message: "Welcome to Helm-powered NGINX!"

autoscaling:
  enabled: true
  minReplicas: 2
  maxReplicas: 5
  targetCPUUtilizationPercentage: 70

resources: {}
nodeSelector: {}
tolerations: []
affinity: {}

⚙️ Templates Overview

🔸 `deployment.yaml`

apiVersion: apps/v1
kind: Deployment
metadata:
  name: {{ include "nginx-demo.fullname" . }}
  labels:
    {{- include "nginx-demo.labels" . | nindent 4 }}
spec:
  replicas: {{ .Values.replicaCount }}
  selector:
    matchLabels:
      app: {{ include "nginx-demo.name" . }}
  template:
    metadata:
      labels:
        app: {{ include "nginx-demo.name" . }}
    spec:
      containers:
        - name: nginx
          image: "{{ .Values.image.repository }}:{{ .Values.image.tag }}"
          imagePullPolicy: {{ .Values.image.pullPolicy }}
          ports:
            - containerPort: 80
          env:
            - name: APP_MESSAGE
              valueFrom:
                configMapKeyRef:
                  name: {{ include "nginx-demo.fullname" . }}
                  key: appMessage

🔸 `service.yaml`

apiVersion: v1
kind: Service
metadata:
  name: {{ include "nginx-demo.fullname" . }}
spec:
  type: {{ .Values.service.type }}
  ports:
    - port: {{ .Values.service.port }}
      targetPort: 80
  selector:
    app: {{ include "nginx-demo.name" . }}

🔸 `configmap.yaml`

apiVersion: v1
kind: ConfigMap
metadata:
  name: {{ include "nginx-demo.fullname" . }}
data:
  appMessage: {{ .Values.config.message | quote }}

🔸 `ingress.yaml`

{{- if .Values.ingress.enabled }}
apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: {{ include "nginx-demo.fullname" . }}
  annotations:
    {{- range $key, $value := .Values.ingress.annotations }}
    {{ $key }}: {{ $value | quote }}
    {{- end }}
spec:
  ingressClassName: {{ .Values.ingress.className }}
  rules:
    {{- range .Values.ingress.hosts }}
    - host: {{ .host }}
      http:
        paths:
          {{- range .paths }}
          - path: {{ .path }}
            pathType: {{ .pathType }}
            backend:
              service:
                name: {{ include "nginx-demo.fullname" $ }}
                port:
                  number: {{ $.Values.service.port }}
          {{- end }}
    {{- end }}
{{- end }}

🔸 `hpa.yaml`

{{- if .Values.autoscaling.enabled }}
apiVersion: autoscaling/v2
kind: HorizontalPodAutoscaler
metadata:
  name: {{ include "nginx-demo.fullname" . }}
spec:
  scaleTargetRef:
    apiVersion: apps/v1
    kind: Deployment
    name: {{ include "nginx-demo.fullname" . }}
  minReplicas: {{ .Values.autoscaling.minReplicas }}
  maxReplicas: {{ .Values.autoscaling.maxReplicas }}
  metrics:
    - type: Resource
      resource:
        name: cpu
        target:
          type: Utilization
          averageUtilization: {{ .Values.autoscaling.targetCPUUtilizationPercentage }}
{{- end }}

🧪 Run the Chart

helm install my-nginx ./nginx-demo
helm test my-nginx

🌐 Host Helm Charts on GitHub

Step 1: Create and Package

mkdir helm-registry && cd helm-registry
helm create order
helm create delivery

helm package order
helm package delivery
helm repo index .

Step 2: Push to GitHub

git init
git remote add origin https://github.com/<your-username>/helm-registry.git
git add .
git commit -m "Add Order and Delivery Charts"
git push -u origin main

Enable GitHub Pages on the repository (Settings → Pages).

Step 3: Add and Use Repo

helm repo add teamcharts https://<your-username>.github.io/helm-registry
helm repo update

helm install order-app teamcharts/order
helm install delivery-app teamcharts/delivery

✅ Summary

Topic	Description
`_helpers.tpl`	Defines reusable template logic (naming, labels, etc.)
`values.yaml`	Central place for all configuration values
Templates	Refer to values and helpers using Go templating
Hosting	GitHub Pages serves `.tgz` charts and `index.yaml` as a repo
Real-World Additions	ConfigMap, Ingress, Autoscaling (HPA) support