Agent Skills: Helm Chart Development

Helm Chart Development

Create, organize, and manage Helm charts for Kubernetes applications.

Chart Structure

my-app/
├── Chart.yaml           # Chart metadata
├── values.yaml          # Default values
├── charts/              # Dependencies
├── templates/
│   ├── NOTES.txt        # Post-install notes
│   ├── _helpers.tpl     # Template helpers
│   ├── deployment.yaml
│   ├── service.yaml
│   └── ingress.yaml
└── .helmignore

Chart.yaml

apiVersion: v2
name: my-app
description: A Helm chart for My Application
version: 1.0.0
appVersion: "2.1.0"

dependencies:
  - name: postgresql
    version: "12.0.0"
    repository: "https://charts.bitnami.com/bitnami"
    condition: postgresql.enabled

values.yaml Structure

image:
  repository: myapp
  tag: "1.0.0"
  pullPolicy: IfNotPresent

replicaCount: 3

service:
  type: ClusterIP
  port: 80

ingress:
  enabled: false
  hosts:
    - host: app.example.com
      paths:
        - path: /
          pathType: Prefix

resources:
  requests:
    memory: "256Mi"
    cpu: "250m"
  limits:
    memory: "512Mi"
    cpu: "500m"

autoscaling:
  enabled: false
  minReplicas: 2
  maxReplicas: 10

Template Helpers (_helpers.tpl)

{{- define "my-app.fullname" -}}
{{- if .Values.fullnameOverride }}
{{- .Values.fullnameOverride | trunc 63 | trimSuffix "-" }}
{{- else }}
{{- printf "%s-%s" .Release.Name .Chart.Name | trunc 63 | trimSuffix "-" }}
{{- end }}
{{- end }}

{{- define "my-app.labels" -}}
helm.sh/chart: {{ .Chart.Name }}-{{ .Chart.Version }}
app.kubernetes.io/name: {{ include "my-app.name" . }}
app.kubernetes.io/instance: {{ .Release.Name }}
{{- end }}

Deployment Template

apiVersion: apps/v1
kind: Deployment
metadata:
  name: {{ include "my-app.fullname" . }}
  labels:
    {{- include "my-app.labels" . | nindent 4 }}
spec:
  {{- if not .Values.autoscaling.enabled }}
  replicas: {{ .Values.replicaCount }}
  {{- end }}
  selector:
    matchLabels:
      {{- include "my-app.selectorLabels" . | nindent 6 }}
  template:
    spec:
      containers:
      - name: {{ .Chart.Name }}
        image: "{{ .Values.image.repository }}:{{ .Values.image.tag }}"
        resources:
          {{- toYaml .Values.resources | nindent 12 }}

Multi-Environment Configuration

my-app/
├── values.yaml          # Defaults
├── values-dev.yaml      # Development
├── values-staging.yaml  # Staging
└── values-prod.yaml     # Production

Install with environment:

helm install my-app ./my-app -f values-prod.yaml -n production

Common Patterns

Conditional Resources

{{- if .Values.ingress.enabled }}
apiVersion: networking.k8s.io/v1
kind: Ingress
...
{{- end }}

Iterating Lists

env:
{{- range .Values.env }}
- name: {{ .name }}
  value: {{ .value | quote }}
{{- end }}

Validation Commands

helm lint my-app/
helm template my-app ./my-app --dry-run
helm install my-app ./my-app --dry-run --debug

Best Practices

1. Use semantic versioning
2. Document all values with comments
3. Use template helpers for repeated logic
4. Pin dependency versions explicitly
5. Include NOTES.txt with usage instructions
6. Add labels consistently
7. Test in all environments