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

• Use semantic versioning

• Document all values with comments

• Use template helpers for repeated logic

• Pin dependency versions explicitly

• Include NOTES.txt with usage instructions

• Add labels consistently

• Test in all environments