Helm Chart Structure

🔥 Vibe Prompt

"Create a Helm chart for a microservice with deployment, service, ingress, configmap, secrets."

helm create myapp

myapp/
├── Chart.yaml          # Metadata
├── values.yaml         # Default values
├── templates/
│   ├── deployment.yaml
│   ├── service.yaml
│   ├── ingress.yaml
│   ├── configmap.yaml
│   └── _helpers.tpl    # Named templates
└── charts/             # Subchart dependencies

Chart.yaml

apiVersion: v2
name: myapp
version: 1.0.0
appVersion: "1.0"
description: My microservice Helm chart

Deployment Template

apiVersion: apps/v1
kind: Deployment
metadata:
  name: {{ .Values.appName }}
spec:
  replicas: {{ .Values.replicaCount }}
  selector:
    matchLabels:
      app: {{ .Values.appName }}
  template:
    spec:
      containers:
        - name: {{ .Chart.Name }}
          image: "{{ .Values.image.repository }}:{{ .Values.image.tag }}"
          envFrom:
            - configMapRef:
                name: {{ .Values.appName }}-config

values.yaml

appName: myapp
replicaCount: 3
image:
  repository: nginx
  tag: stable
service:
  port: 80
ingress:
  enabled: true
  hosts: ["app.example.com"]

Commands

helm lint ./myapp                    # Validate
helm template ./myapp                # Render locally
helm install release-name ./myapp    # Deploy
helm upgrade release-name ./myapp    # Update
helm rollback release-name 1         # Rollback
helm list                           # List releases

Chapter Summary

• Understand core concepts and principles
• Master implementation methods and techniques
• Familiar with common issues and solutions
• Able to apply in real projects

Further Reading

• Official documentation and API references
• Open source examples on GitHub
• Technical books and online courses
• Community discussions and tech blogs

Implementation Example

Basic Example

# This section provides a complete implementation example

Steps

1. Setup: Configure development environment
2. Data: Prepare required data
3. Implementation: Build core functionality
4. Testing: Verify correctness
5. Optimization: Improve performance

Common Errors

| Error Type | Cause | Solution | |------------|-------|----------| | Compilation | Syntax | Check code syntax | | Runtime | Environment | Verify dependencies installed | | Logic | Algorithm | Step-by-step debugging | | Performance | Efficiency | Use profilers |

Code Example

import sys

def main():
    print("Hello, World!")

if __name__ == "__main__":
    main()

References

• Official documentation
• API reference
• Open source examples
• Community discussions

Chart.yaml Deep Dive

The Chart.yaml file defines metadata about the chart. It is required for every chart.

Required Fields

| Field | Description | Example | |-------|-------------|--------| | apiVersion | Chart API version (v2 for Helm 3+) | v2 | | name | Chart name | my-app | | version | Chart version (SemVer 2) | 0.1.0 |

Optional but Recommended Fields

| Field | Description | Example | |-------|-------------|--------| | description | One-line description | "A Helm chart for Kubernetes" | | type | application or library | application | | appVersion | Application version being deployed | 1.16.0 | | kubeVersion | Compatible K8s version constraint | >=1.19.0-0 | | keywords | Search keywords | ["nginx", "web", "server"] | | home | Project home URL | https://my-app.example.com | | sources | Source code URLs | [https://github.com/org/my-app] | | maintainers | Maintainer list with name/email/url | [{name: "Alice", email: "a@b.com"}] | | dependencies | List of chart dependencies | [{name: "redis", version: "10.x"}] | | annotations | Extra metadata | {category: "Infrastructure"} |

Example Chart.yaml

apiVersion: v2
name: my-web-app
description: A production-ready web application
type: application
version: 0.1.0
appVersion: "1.0.0"
kubeVersion: ">=1.21.0-0"
keywords:
  - web
  - api
  - nginx
home: https://github.com/myorg/my-web-app
sources:
  - https://github.com/myorg/my-web-app
maintainers:
  - name: DevOps Team
    email: devops@myorg.com
    url: https://myorg.com
dependencies:
  - name: postgresql
    version: 12.x
    repository: https://charts.bitnami.com/bitnami
    condition: postgresql.enabled

Templates Directory

Every file in templates/ is rendered as a Kubernetes manifest. Helm uses Go templates to inject values.

Standard Template Files

| File | Purpose | |------|---------| | deployment.yaml | Main Deployment resource | | service.yaml | Service resource | | ingress.yaml | Ingress for external access | | configmap.yaml | Configuration data | | secret.yaml | Sensitive data | | serviceaccount.yaml | Service account | | hpa.yaml | Horizontal Pod Autoscaler | | pvc.yaml | Persistent Volume Claim | | _helpers.tpl | Shared template functions |

_helpers.tpl — Reusable Templates

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

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

Values System

The values.yaml file provides default configuration values that users can override.

Values Priority Order

1. --set flags (highest priority)
2. --values custom file
3. Parent chart values (for subcharts)
4. Chart's values.yaml (default)

Standard values.yaml Structure

# Global settings
replicaCount: 3

# Image configuration
image:
  repository: nginx
  tag: latest
  pullPolicy: IfNotPresent

# Service configuration
service:
  type: ClusterIP
  port: 80
  targetPort: 8080

# Resource limits
resources:
  requests:
    cpu: 100m
    memory: 128Mi
  limits:
    cpu: 500m
    memory: 512Mi

# Ingress
ingress:
  enabled: false
  className: nginx
  host: my-app.example.com
  tls: []

# Persistence
persistence:
  enabled: true
  size: 8Gi
  storageClass: standard

Built-in Objects

Helm provides several built-in objects accessible in templates.

| Object | Description | Example Value | |--------|-------------|--------------| | .Release.Name | Release name | my-release | | .Release.Namespace | Target namespace | default | | .Release.Service | Service handling the release | Helm | | .Release.IsUpgrade | True if upgrade | true | | .Release.IsInstall | True if install | false | | .Chart.Name | Chart name | my-app | | .Chart.Version | Chart version | 0.1.0 | | .Chart.AppVersion | App version | 1.0.0 | | .Files | Access chart files | .Files.Get "config.json" | | .Capabilities | K8s cluster capabilities | .Capabilities.KubeVersion | | .Template.Name | Current template path | templates/deployment.yaml |

Summary

A Helm chart consists of Chart.yaml, templates/, values.yaml, and supporting files. Understanding this structure is the foundation for creating reusable, configurable Kubernetes packages.

Key takeaways:

• Chart.yaml defines metadata: name, version, dependencies, maintainers |
• templates/ contains Go template files that render to Kubernetes manifests |
• _helpers.tpl stores reusable named templates for labels, names, etc. |
• values.yaml provides default configuration with clear overridable structure |
• Built-in objects give access to release, chart, file, and capability info |
• Charts follow a standard layout for consistency across the ecosystem |

What's Next: Go Templates and Values

The next chapter covers Go template syntax and values management in depth.