Helm

What is Helm?

Helm is a package manager for Kubernetes that helps define, install, and upgrade complex Kubernetes applications using charts.

Helm Chart Structure

myapp/
├── Chart.yaml
├── values.yaml
├── templates/
│   ├── deployment.yaml
│   ├── service.yaml
│   ├── ingress.yaml
│   └── _helpers.tpl
└── charts/

Chart.yaml

apiVersion: v2
name: myapp
description: Full-stack application
version: 1.0.0
appVersion: "1.0.0"
dependencies:
  - name: postgresql
    version: 12.x.x
    repository: https://charts.bitnami.com/bitnami
  - name: mongodb
    version: 13.x.x
    repository: https://charts.bitnami.com/bitnami
  - name: redis
    version: 17.x.x
    repository: https://charts.bitnami.com/bitnami

values.yaml

# Angular Frontend
frontend:
  enabled: true
  replicaCount: 3
  image:
    repository: myapp/frontend
    tag: "1.0.0"
  service:
    type: LoadBalancer
    port: 80

# .NET API
api:
  enabled: true
  replicaCount: 5
  image:
    repository: myapp/api
    tag: "1.0.0"
  service:
    type: ClusterIP
    port: 5000
  env:
    ASPNETCORE_ENVIRONMENT: Production

# Node.js Service
service:
  enabled: true
  replicaCount: 4
  image:
    repository: myapp/service
    tag: "1.0.0"
  service:
    type: ClusterIP
    port: 3000
  env:
    NODE_ENV: production

# PostgreSQL
postgresql:
  enabled: true
  auth:
    database: myapp
    username: admin
  primary:
    persistence:
      size: 10Gi

# MongoDB
mongodb:
  enabled: true
  auth:
    enabled: false
  persistence:
    size: 20Gi

# Redis
redis:
  enabled: true
  master:
    persistence:
      enabled: false

Deployment Template

# templates/deployment.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
  name: {{ include "myapp.fullname" . }}-api
  labels:
    {{- include "myapp.labels" . | nindent 4 }}
spec:
  replicas: {{ .Values.api.replicaCount }}
  selector:
    matchLabels:
      app: {{ include "myapp.name" . }}-api
  template:
    metadata:
      labels:
        app: {{ include "myapp.name" . }}-api
    spec:
      containers:
        - name: api
          image: "{{ .Values.api.image.repository }}:{{ .Values.api.image.tag }}"
          ports:
            - containerPort: {{ .Values.api.service.port }}
          env:
            {{- range $key, $value := .Values.api.env }}
            - name: {{ $key }}
              value: {{ $value | quote }}
            {{- end }}
            - name: DATABASE_URL
              value: "postgresql://{{ .Values.postgresql.auth.username }}@{{ include "myapp.fullname" . }}-postgresql:5432/{{ .Values.postgresql.auth.database }}"

Service Template

# templates/service.yaml
apiVersion: v1
kind: Service
metadata:
  name: {{ include "myapp.fullname" . }}-api
spec:
  type: {{ .Values.api.service.type }}
  ports:
    - port: {{ .Values.api.service.port }}
      targetPort: {{ .Values.api.service.port }}
  selector:
    app: {{ include "myapp.name" . }}-api

Helpers

# templates/_helpers.tpl
{{- define "myapp.name" -}}
{{- default .Chart.Name .Values.nameOverride | trunc 63 | trimSuffix "-" }}
{{- end }}

{{- define "myapp.fullname" -}}
{{- if .Values.fullnameOverride }}
{{- .Values.fullnameOverride | trunc 63 | trimSuffix "-" }}
{{- else }}
{{- $name := default .Chart.Name .Values.nameOverride }}
{{- printf "%s-%s" .Release.Name $name | trunc 63 | trimSuffix "-" }}
{{- end }}
{{- end }}

{{- define "myapp.labels" -}}
helm.sh/chart: {{ include "myapp.chart" . }}
{{ include "myapp.selectorLabels" . }}
app.kubernetes.io/version: {{ .Chart.AppVersion | quote }}
app.kubernetes.io/managed-by: {{ .Release.Service }}
{{- end }}

Install Chart

# Add repository
helm repo add bitnami https://charts.bitnami.com/bitnami
helm repo update

# Install chart
helm install myapp ./myapp

# Install with custom values
helm install myapp ./myapp -f values-production.yaml

# Install with overrides
helm install myapp ./myapp \
  --set api.replicaCount=10 \
  --set postgresql.auth.password=secret123

Upgrade

# Upgrade release
helm upgrade myapp ./myapp

# Upgrade with new values
helm upgrade myapp ./myapp -f values-production.yaml

# Rollback
helm rollback myapp 1

Environment-Specific Values

# values-dev.yaml
api:
  replicaCount: 1
postgresql:
  primary:
    persistence:
      size: 1Gi

---
# values-production.yaml
api:
  replicaCount: 10
postgresql:
  primary:
    persistence:
      size: 100Gi

CI/CD Integration

# GitHub Actions
name: Helm Deploy

on:
  push:
    branches: [main]

jobs:
  deploy:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v3
      
      - name: Install Helm
        uses: azure/setup-helm@v3
      
      - name: Deploy to Kubernetes
        run: |
          helm upgrade --install myapp ./helm/myapp \
            --set api.image.tag=${{ github.sha }} \
            --set frontend.image.tag=${{ github.sha }} \
            --set service.image.tag=${{ github.sha }} \
            -f helm/myapp/values-production.yaml

Helm Commands

# List releases
helm list

# Get release status
helm status myapp

# Get values
helm get values myapp

# Uninstall
helm uninstall myapp

# Lint chart
helm lint ./myapp

# Package chart
helm package ./myapp

# Test chart
helm test myapp

Interview Tips

• Explain Helm: Kubernetes package manager
• Show chart structure: Templates, values
• Demonstrate multi-stack: Frontend, API, databases
• Discuss dependencies: PostgreSQL, MongoDB, Redis
• Mention environments: Dev, staging, production
• Show CI/CD: Automated deployments

Summary

Helm packages Kubernetes applications into charts with templates and values. Supports multi-stack applications including Angular, .NET, Node.js, and databases. Use values files for environment-specific configurations. Integrate with CI/CD for automated deployments. Provides versioning, rollback, and dependency management.