Learning Kubernetes - Episode 38 - Introduction and Explanation of Helm Charts
In this episode, we'll discuss Helm Charts for packaging and deploying Kubernetes applications. We'll learn how to create, customize, and deploy Helm charts, manage dependencies, and best practices for Helm.
#Introduction
Note
If you want to read the previous episode, you can click the Episode 37 thumbnail below
Episode 37In the previous episode, we explored Pod Security Context, which controls security settings for Pods and containers. Now we'll dive into Helm Charts, which simplify packaging and deploying Kubernetes applications.
Note: Here I'll be using a Kubernetes Cluster installed through K3s.
Helm is the package manager for Kubernetes. It allows you to define, install, and upgrade complex Kubernetes applications using charts. Think of Helm charts like Docker images for Kubernetes - they package everything needed to run an application. Instead of managing dozens of YAML files manually, Helm lets you template and version your deployments.
#Understanding Helm Charts
A Helm chart is a collection of files that describe a set of Kubernetes resources. It's essentially a templated package that can be customized and deployed to a cluster.
#Why Helm Charts Matter
1. Simplify Deployment
Package complex applications into a single deployable unit.
2. Reusability
Share charts across teams and organizations.
3. Templating
Use variables and logic to customize deployments.
4. Versioning
Track and manage different versions of applications.
5. Dependency Management
Manage dependencies between applications.
6. Rollback Capability
Easily rollback to previous versions.
#Helm Chart Structure
A typical Helm chart has this structure:
my-chart/
├── Chart.yaml
├── values.yaml
├── values-prod.yaml
├── templates/
│ ├── deployment.yaml
│ ├── service.yaml
│ ├── configmap.yaml
│ ├── ingress.yaml
│ └── _helpers.tpl
├── charts/
│ └── dependency-chart/
└── README.md#Chart.yaml
Metadata about the chart:
apiVersion: v2
name: my-app
description: A Helm chart for my application
type: application
version: 1.0.0
appVersion: "1.0"
keywords:
- app
- kubernetes
maintainers:
- name: Your Name
email: your@email.com#values.yaml
Default configuration values:
replicaCount: 3
image:
repository: myapp
tag: "1.0"
pullPolicy: IfNotPresent
service:
type: ClusterIP
port: 80
targetPort: 8080
ingress:
enabled: true
className: nginx
hosts:
- host: myapp.example.com
paths:
- path: /
pathType: Prefix
resources:
limits:
cpu: 500m
memory: 512Mi
requests:
cpu: 250m
memory: 256Mi#Templates
Kubernetes manifests with template variables:
apiVersion: apps/v1
kind: Deployment
metadata:
name: {{ include "my-app.fullname" . }}
labels:
{{- include "my-app.labels" . | nindent 4 }}
spec:
replicas: {{ .Values.replicaCount }}
selector:
matchLabels:
{{- include "my-app.selectorLabels" . | nindent 6 }}
template:
metadata:
labels:
{{- include "my-app.selectorLabels" . | nindent 8 }}
spec:
containers:
- name: {{ .Chart.Name }}
image: "{{ .Values.image.repository }}:{{ .Values.image.tag }}"
imagePullPolicy: {{ .Values.image.pullPolicy }}
ports:
- name: http
containerPort: {{ .Values.service.targetPort }}
protocol: TCP
resources:
{{- toYaml .Values.resources | nindent 12 }}#Creating a Helm Chart
#Initialize a Chart
helm create my-appThis creates a basic chart structure with example files.
#Chart Validation
helm lint my-appValidates the chart for errors.
#Template Rendering
helm template my-app ./my-appShows the rendered YAML without installing.
#Dry Run
helm install my-release ./my-app --dry-run --debugSimulates the installation without actually deploying.
#Installing Helm Charts
#Basic Installation
helm install my-release ./my-appInstalls the chart with default values.
#Custom Values
helm install my-release ./my-app -f values-prod.yamlInstalls with custom values from a file.
#Override Values
helm install my-release ./my-app \
--set replicaCount=5 \
--set image.tag=2.0Overrides specific values from the command line.
#Namespace
helm install my-release ./my-app -n production --create-namespaceInstalls in a specific namespace.
#Managing Helm Releases
#List Releases
helm list
helm list -n productionShows all installed releases.
#Get Release Info
helm status my-release
helm get values my-release
helm get manifest my-releaseShows release status and configuration.
#Upgrade Release
helm upgrade my-release ./my-appUpgrades to a new version.
#Rollback Release
helm rollback my-release 1Rolls back to a previous revision.
#Uninstall Release
helm uninstall my-releaseRemoves the release from the cluster.
#Helm Repositories
#Add Repository
helm repo add bitnami https://charts.bitnami.com/bitnami
helm repo updateAdds a Helm repository and updates the index.
#Search Charts
helm search repo bitnami
helm search repo bitnami/nginxSearches for charts in repositories.
#Install from Repository
helm install my-nginx bitnami/nginxInstalls a chart from a repository.
#Popular Repositories
- Bitnami - https://charts.bitnami.com/bitnami
- Stable - https://charts.helm.sh/stable
- Jetstack - https://charts.jetstack.io (cert-manager)
- Prometheus - https://prometheus-community.github.io/helm-charts
#Template Functions
#Built-in Functions
# String functions
{{ .Values.name | upper }}
{{ .Values.name | lower }}
{{ .Values.name | quote }}
# Conditional
{{ if .Values.enabled }}
enabled: true
{{ end }}
# Loops
{{ range .Values.items }}
- {{ . }}
{{ end }}
# Default values
{{ .Values.name | default "default-name" }}
# Include templates
{{ include "my-app.labels" . }}#Helper Templates
{{/*
Expand the name of the chart.
*/}}
{{- define "my-app.name" -}}
{{- default .Chart.Name .Values.nameOverride | trunc 63 | trimSuffix "-" }}
{{- end }}
{{/*
Create a default fully qualified app name.
*/}}
{{- define "my-app.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 }}
{{/*
Common labels
*/}}
{{- define "my-app.labels" -}}
helm.sh/chart: {{ include "my-app.chart" . }}
{{ include "my-app.selectorLabels" . }}
{{- if .Chart.AppVersion }}
app.kubernetes.io/version: {{ .Chart.AppVersion | quote }}
{{- end }}
app.kubernetes.io/managed-by: {{ .Release.Service }}
{{- end }}
{{/*
Selector labels
*/}}
{{- define "my-app.selectorLabels" -}}
app.kubernetes.io/name: {{ include "my-app.name" . }}
app.kubernetes.io/instance: {{ .Release.Name }}
{{- end }}#Chart Dependencies
#Chart.yaml with Dependencies
apiVersion: v2
name: my-app
version: 1.0.0
dependencies:
- name: postgresql
version: "12.0.0"
repository: "https://charts.bitnami.com/bitnami"
condition: postgresql.enabled
- name: redis
version: "17.0.0"
repository: "https://charts.bitnami.com/bitnami"
condition: redis.enabled#Update Dependencies
helm dependency update ./my-appDownloads and updates chart dependencies.
#values.yaml with Dependencies
postgresql:
enabled: true
auth:
username: myapp
password: secret
database: myapp_db
redis:
enabled: true
auth:
enabled: false#Practical Examples
#Simple Web Application Chart
apiVersion: apps/v1
kind: Deployment
metadata:
name: {{ include "web-app.fullname" . }}
spec:
replicas: {{ .Values.replicaCount }}
selector:
matchLabels:
app: {{ include "web-app.name" . }}
template:
metadata:
labels:
app: {{ include "web-app.name" . }}
spec:
containers:
- name: web
image: "{{ .Values.image.repository }}:{{ .Values.image.tag }}"
ports:
- containerPort: {{ .Values.service.port }}
env:
- name: DATABASE_URL
valueFrom:
secretKeyRef:
name: {{ include "web-app.fullname" . }}-secret
key: database-url
resources:
{{- toYaml .Values.resources | nindent 12 }}
---
apiVersion: v1
kind: Service
metadata:
name: {{ include "web-app.fullname" . }}
spec:
type: {{ .Values.service.type }}
ports:
- port: {{ .Values.service.port }}
targetPort: {{ .Values.service.port }}
selector:
app: {{ include "web-app.name" . }}#Conditional Resources
{{- if .Values.ingress.enabled }}
apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
name: {{ include "web-app.fullname" . }}
spec:
ingressClassName: {{ .Values.ingress.className }}
rules:
{{- range .Values.ingress.hosts }}
- host: {{ .host | quote }}
http:
paths:
{{- range .paths }}
- path: {{ .path }}
pathType: {{ .pathType }}
backend:
service:
name: {{ include "web-app.fullname" . }}
port:
number: {{ $.Values.service.port }}
{{- end }}
{{- end }}
{{- end }}#Common Mistakes and Pitfalls
#Mistake 1: Hardcoding Values
Problem: Chart is not reusable.
# DON'T DO THIS - Hardcoded values
image: myapp:1.0
replicas: 3Solution: Use template variables:
image: "{{ .Values.image.repository }}:{{ .Values.image.tag }}"
replicas: {{ .Values.replicaCount }}#Mistake 2: Missing Default Values
Problem: Chart fails if values are not provided.
# DON'T DO THIS - No default values
image: "{{ .Values.image }}"Solution: Provide defaults:
image: "{{ .Values.image | default "nginx:latest" }}"#Mistake 3: Inconsistent Naming
Problem: Resources have inconsistent names.
# DON'T DO THIS - Inconsistent naming
metadata:
name: my-app
---
metadata:
name: myappSolution: Use helper templates:
metadata:
name: {{ include "my-app.fullname" . }}#Mistake 4: Not Testing Charts
Problem: Chart has errors when deployed.
Solution: Always test before deploying:
helm lint ./my-app
helm template ./my-app
helm install --dry-run --debug ./my-app#Mistake 5: Poor Documentation
Problem: Users don't know how to use the chart.
Solution: Document values and usage:
# My App Helm Chart
## Installation
```bash
helm install my-release ./my-app
```
## Configuration
| Parameter | Description | Default |
|-----------|-------------|---------|
| replicaCount | Number of replicas | 3 |
| image.repository | Image repository | myapp |
| image.tag | Image tag | 1.0 |#Best Practices
#1. Use Semantic Versioning
version: 1.2.3
appVersion: "2.0.1"#2. Provide Comprehensive values.yaml
Document all available values with comments:
# Number of replicas
replicaCount: 3
# Image configuration
image:
# Image repository
repository: myapp
# Image tag
tag: "1.0"
# Image pull policy
pullPolicy: IfNotPresent#3. Use Helper Templates
Create reusable template helpers:
{{- define "my-app.fullname" -}}
{{- .Release.Name }}-{{ .Chart.Name }}
{{- end }}#4. Validate Charts
Always validate before deploying:
helm lint ./my-app
helm template ./my-app#5. Use Namespaces
Deploy to specific namespaces:
helm install my-release ./my-app -n production --create-namespace#6. Version Your Charts
Track chart versions in version control:
git tag chart-v1.0.0#7. Document Values
Create a comprehensive README:
# Chart Documentation
## Values
- `replicaCount`: Number of replicas (default: 3)
- `image.repository`: Image repository (default: myapp)
- `image.tag`: Image tag (default: 1.0)#Helm Hooks
Execute actions at specific points in the release lifecycle:
apiVersion: batch/v1
kind: Job
metadata:
name: {{ include "my-app.fullname" . }}-pre-install
annotations:
"helm.sh/hook": pre-install
"helm.sh/hook-weight": "-5"
spec:
template:
spec:
containers:
- name: pre-install
image: busybox
command: ['sh', '-c', 'echo "Pre-install hook"']
restartPolicy: Never#Hook Types
pre-install- Before installpost-install- After installpre-upgrade- Before upgradepost-upgrade- After upgradepre-delete- Before deletepost-delete- After deletepre-rollback- Before rollbackpost-rollback- After rollback
#Conclusion
In episode 38, we've explored Helm Charts in Kubernetes in depth. We've learned how to create, customize, and deploy Helm charts, manage dependencies, and follow best practices.
Key takeaways:
- Helm Charts package Kubernetes applications
- Chart.yaml - Chart metadata
- values.yaml - Default configuration
- templates/ - Kubernetes manifests with variables
- helm create - Initialize a new chart
- helm install - Deploy a chart
- helm upgrade - Update a release
- helm rollback - Revert to previous version
- Template functions - Customize deployments
- Dependencies - Manage chart dependencies
- Repositories - Share and discover charts
- Hooks - Execute actions at lifecycle events
- Always validate - Test charts before deploying
- Document values - Help users understand configuration
- Use semantic versioning - Track chart versions
Helm charts simplify Kubernetes deployments and make applications more reusable and maintainable.
Note
If you want to continue to the next episode, you can click the Episode 39 thumbnail below
Episode 39