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Anatomy of a Chart

1 - Create a new Chart​

1.1 Generation with helm create​

# Créer un nouveau chart
helm create mon-app

# Structure générée
mon-app/
├── .helmignore           # Fichiers à ignorer lors du packaging
├── Chart.yaml            # Métadonnées du chart
├── values.yaml           # Configuration par défaut
├── charts/               # Dépendances
├── templates/            # Templates Kubernetes
│   ├── NOTES.txt         # Notes post-installation
│   ├── _helpers.tpl      # Fonctions helpers
│   ├── deployment.yaml
│   ├── hpa.yaml
│   ├── ingress.yaml
│   ├── service.yaml
│   ├── serviceaccount.yaml
│   └── tests/
│       └── test-connection.yaml
└── README.md

1.2 Minimal structure​

minimal-chart/
├── Chart.yaml
├── values.yaml
└── templates/
    └── configmap.yaml
# Chart.yaml (minimal)
apiVersion: v2
name: minimal-chart
version: 0.1.0

2 - Configuration files​

2.1 Complete Chart.yaml​

apiVersion: v2
name: mon-application
version: 1.0.0
appVersion: "2.1.0"
description: |
  Une application web complète avec base de données
  et cache Redis.
  
type: application
kubeVersion: ">=1.23.0"

keywords:
  - web
  - api
  - microservice

home: https://github.com/monorg/mon-app
sources:
  - https://github.com/monorg/mon-app
  - https://github.com/monorg/mon-app-chart

maintainers:
  - name: DevOps Team
    email: [email protected]
    url: https://example.com

icon: https://example.com/icons/app.png

annotations:
  artifacthub.io/category: web-application
  artifacthub.io/license: Apache-2.0
  artifacthub.io/links: |
    - name: Documentation
      url: https://docs.example.com
    - name: Support
      url: https://support.example.com

# Dépendances
dependencies:
  - name: postgresql
    version: "~12.1.0"
    repository: https://charts.bitnami.com/bitnami
    condition: postgresql.enabled
    alias: db
  - name: redis
    version: "17.x"
    repository: https://charts.bitnami.com/bitnami
    condition: redis.enabled
    import-values:
      - child: primary
        parent: redis

2.2 .helmignore​

# .helmignore
# Fichiers à exclure du package

# Patterns communs
.DS_Store
.git/
.gitignore
.bzr/
.bzrignore
.hg/
.hgignore
.svn/

# IDE
*.swp
*.bak
*.tmp
*.orig
*~
.idea/
*.tmproj
.vscode/

# CI/CD
.travis.yml
.gitlab-ci.yml
.github/

# Tests et développement
OWNERS
SECURITY.md
CONTRIBUTING.md
hack/
Makefile

# Fichiers de build
*.tgz

2.3 Organized values.yaml​

# values.yaml

# ===========================================
# Configuration globale
# ===========================================
global:
  imageRegistry: ""
  imagePullSecrets: []
  storageClass: ""

# ===========================================
# Application principale
# ===========================================
replicaCount: 1

image:
  repository: nginx
  tag: ""  # Défaut: appVersion du Chart.yaml
  pullPolicy: IfNotPresent
  pullSecrets: []

nameOverride: ""
fullnameOverride: ""

# ===========================================
# Service Account
# ===========================================
serviceAccount:
  create: true
  automount: true
  annotations: {}
  name: ""

# ===========================================
# Pod
# ===========================================
podAnnotations: {}
podLabels: {}

podSecurityContext:
  fsGroup: 1000

securityContext:
  runAsNonRoot: true
  runAsUser: 1000
  allowPrivilegeEscalation: false
  capabilities:
    drop:
      - ALL
  readOnlyRootFilesystem: true

# ===========================================
# Service
# ===========================================
service:
  type: ClusterIP
  port: 80

# ===========================================
# Ingress
# ===========================================
ingress:
  enabled: false
  className: ""
  annotations: {}
  hosts:
    - host: chart-example.local
      paths:
        - path: /
          pathType: ImplementationSpecific
  tls: []

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

# ===========================================
# Probes
# ===========================================
livenessProbe:
  httpGet:
    path: /health
    port: http
  initialDelaySeconds: 10
  periodSeconds: 10

readinessProbe:
  httpGet:
    path: /ready
    port: http
  initialDelaySeconds: 5
  periodSeconds: 5

# ===========================================
# Autoscaling
# ===========================================
autoscaling:
  enabled: false
  minReplicas: 1
  maxReplicas: 10
  targetCPUUtilizationPercentage: 80
  targetMemoryUtilizationPercentage: 80

# ===========================================
# Volumes et Persistence
# ===========================================
persistence:
  enabled: false
  storageClass: ""
  accessModes:
    - ReadWriteOnce
  size: 8Gi
  annotations: {}
  existingClaim: ""

# ===========================================
# Configuration additionnelle
# ===========================================
env: []
envFrom: []
volumes: []
volumeMounts: []

nodeSelector: {}
tolerations: []
affinity: {}

# ===========================================
# Dépendances
# ===========================================
postgresql:
  enabled: false
  auth:
    username: app
    database: appdb

redis:
  enabled: false
  architecture: standalone

3 - The templates/ folder​

3.1 Typical structure​

templates/
├── NOTES.txt               # Message post-installation
├── _helpers.tpl            # Fonctions partagées
├── deployment.yaml         # Deployment principal
├── service.yaml            # Service
├── serviceaccount.yaml     # ServiceAccount
├── configmap.yaml          # ConfigMaps
├── secret.yaml             # Secrets
├── ingress.yaml            # Ingress
├── hpa.yaml                # HorizontalPodAutoscaler
├── pdb.yaml                # PodDisruptionBudget
├── pvc.yaml                # PersistentVolumeClaim
├── networkpolicy.yaml      # NetworkPolicy
├── cronjob.yaml            # CronJobs
└── tests/
    └── test-connection.yaml

3.2 _helpers.tpl​

{{/* templates/_helpers.tpl */}}

{{/*
Expand the name of the chart.
*/}}
{{- define "mon-app.name" -}}
{{- default .Chart.Name .Values.nameOverride | trunc 63 | trimSuffix "-" }}
{{- end }}

{{/*
Create a default fully qualified app name.
*/}}
{{- define "mon-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 }}

{{/*
Create chart name and version as used by the chart label.
*/}}
{{- define "mon-app.chart" -}}
{{- printf "%s-%s" .Chart.Name .Chart.Version | replace "+" "_" | trunc 63 | trimSuffix "-" }}
{{- end }}

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

{{/*
Selector labels
*/}}
{{- define "mon-app.selectorLabels" -}}
app.kubernetes.io/name: {{ include "mon-app.name" . }}
app.kubernetes.io/instance: {{ .Release.Name }}
{{- end }}

{{/*
Create the name of the service account to use
*/}}
{{- define "mon-app.serviceAccountName" -}}
{{- if .Values.serviceAccount.create }}
{{- default (include "mon-app.fullname" .) .Values.serviceAccount.name }}
{{- else }}
{{- default "default" .Values.serviceAccount.name }}
{{- end }}
{{- end }}

{{/*
Return the proper image name
*/}}
{{- define "mon-app.image" -}}
{{- $registryName := .Values.global.imageRegistry | default "" -}}
{{- $repositoryName := .Values.image.repository -}}
{{- $tag := .Values.image.tag | default .Chart.AppVersion -}}
{{- if $registryName }}
{{- printf "%s/%s:%s" $registryName $repositoryName $tag -}}
{{- else }}
{{- printf "%s:%s" $repositoryName $tag -}}
{{- end }}
{{- end }}

3.3 deployment.yaml​

{{/* templates/deployment.yaml */}}
apiVersion: apps/v1
kind: Deployment
metadata:
  name: {{ include "mon-app.fullname" . }}
  labels:
    {{- include "mon-app.labels" . | nindent 4 }}
spec:
  {{- if not .Values.autoscaling.enabled }}
  replicas: {{ .Values.replicaCount }}
  {{- end }}
  selector:
    matchLabels:
      {{- include "mon-app.selectorLabels" . | nindent 6 }}
  template:
    metadata:
      annotations:
        checksum/config: {{ include (print $.Template.BasePath "/configmap.yaml") . | sha256sum }}
        {{- with .Values.podAnnotations }}
        {{- toYaml . | nindent 8 }}
        {{- end }}
      labels:
        {{- include "mon-app.labels" . | nindent 8 }}
        {{- with .Values.podLabels }}
        {{- toYaml . | nindent 8 }}
        {{- end }}
    spec:
      {{- with .Values.image.pullSecrets }}
      imagePullSecrets:
        {{- toYaml . | nindent 8 }}
      {{- end }}
      serviceAccountName: {{ include "mon-app.serviceAccountName" . }}
      securityContext:
        {{- toYaml .Values.podSecurityContext | nindent 8 }}
      containers:
        - name: {{ .Chart.Name }}
          securityContext:
            {{- toYaml .Values.securityContext | nindent 12 }}
          image: {{ include "mon-app.image" . }}
          imagePullPolicy: {{ .Values.image.pullPolicy }}
          ports:
            - name: http
              containerPort: {{ .Values.service.port }}
              protocol: TCP
          {{- with .Values.env }}
          env:
            {{- toYaml . | nindent 12 }}
          {{- end }}
          {{- with .Values.envFrom }}
          envFrom:
            {{- toYaml . | nindent 12 }}
          {{- end }}
          livenessProbe:
            {{- toYaml .Values.livenessProbe | nindent 12 }}
          readinessProbe:
            {{- toYaml .Values.readinessProbe | nindent 12 }}
          resources:
            {{- toYaml .Values.resources | nindent 12 }}
          {{- with .Values.volumeMounts }}
          volumeMounts:
            {{- toYaml . | nindent 12 }}
          {{- end }}
      {{- with .Values.volumes }}
      volumes:
        {{- toYaml . | nindent 8 }}
      {{- end }}
      {{- with .Values.nodeSelector }}
      nodeSelector:
        {{- toYaml . | nindent 8 }}
      {{- end }}
      {{- with .Values.affinity }}
      affinity:
        {{- toYaml . | nindent 8 }}
      {{- end }}
      {{- with .Values.tolerations }}
      tolerations:
        {{- toYaml . | nindent 8 }}
      {{- end }}

3.4 NOTES.txt​

{{/* templates/NOTES.txt */}}
🎉 {{ .Chart.Name }} a été déployé avec succès !

Informations de la release:
  - Nom: {{ .Release.Name }}
  - Namespace: {{ .Release.Namespace }}
  - Révision: {{ .Release.Revision }}

Pour accéder à l'application:
{{- if .Values.ingress.enabled }}
{{- range $host := .Values.ingress.hosts }}
  http{{ if $.Values.ingress.tls }}s{{ end }}://{{ $host.host }}{{ (first $host.paths).path }}
{{- end }}
{{- else if contains "NodePort" .Values.service.type }}
  export NODE_PORT=$(kubectl get --namespace {{ .Release.Namespace }} -o jsonpath="{.spec.ports[0].nodePort}" services {{ include "mon-app.fullname" . }})
  export NODE_IP=$(kubectl get nodes --namespace {{ .Release.Namespace }} -o jsonpath="{.items[0].status.addresses[0].address}")
  echo http://$NODE_IP:$NODE_PORT
{{- else if contains "LoadBalancer" .Values.service.type }}
  NOTE: Le LoadBalancer peut prendre quelques minutes à provisionner.
  Exécutez cette commande pour obtenir l'IP:
  kubectl get --namespace {{ .Release.Namespace }} svc {{ include "mon-app.fullname" . }} -w
{{- else if contains "ClusterIP" .Values.service.type }}
  kubectl port-forward --namespace {{ .Release.Namespace }} svc/{{ include "mon-app.fullname" . }} 8080:{{ .Values.service.port }}
  Puis accédez à http://localhost:8080
{{- end }}

Pour voir les logs:
  kubectl logs -n {{ .Release.Namespace }} -l app.kubernetes.io/instance={{ .Release.Name }} -f

4 - Dependency management​

4.1 Define dependencies​

# Chart.yaml
dependencies:
  - name: postgresql
    version: "12.1.0"
    repository: https://charts.bitnami.com/bitnami
    condition: postgresql.enabled
    alias: db
    
  - name: redis
    version: "17.3.0"
    repository: https://charts.bitnami.com/bitnami
    condition: redis.enabled
    tags:
      - cache
      - backend

4.2 Manage dependencies​

# Télécharger les dépendances
helm dependency update ./mon-chart

# Lister les dépendances
helm dependency list ./mon-chart

# Résultat: charts/ contient les .tgz des dépendances
# et Chart.lock est créé/mis à jour

4.3 Chart.lock​

# Chart.lock (généré automatiquement)
dependencies:
- name: postgresql
  repository: https://charts.bitnami.com/bitnami
  version: 12.1.0
- name: redis
  repository: https://charts.bitnami.com/bitnami
  version: 17.3.0
digest: sha256:abc123...
generated: "2023-11-13T10:00:00Z"

4.4 Configure dependencies​

# values.yaml
postgresql:
  enabled: true
  auth:
    username: appuser
    password: secretpassword
    database: appdb
  primary:
    resources:
      limits:
        cpu: 500m
        memory: 512Mi

redis:
  enabled: true
  architecture: standalone
  auth:
    enabled: false

5 - Packaging and distribution​

5.1 Package a chart​

# Packager le chart
helm package ./mon-chart

# Résultat: mon-chart-1.0.0.tgz

# Avec un répertoire de destination
helm package ./mon-chart -d ./packages

# Signer le package (optionnel)
helm package ./mon-chart --sign --key "John Doe" --keyring ~/.gnupg/pubring.gpg

5.2 Validate a chart​

# Linting
helm lint ./mon-chart

# Template rendering (dry-run)
helm template mon-release ./mon-chart

# Avec values spécifiques
helm template mon-release ./mon-chart -f production.yaml

# Dry-run contre le cluster
helm install mon-release ./mon-chart --dry-run --debug

Summary​

In this chapter, we explored:

  • The creation of a new chart
  • The structure of Chart.yaml and its options
  • The .helmignore file
  • The organization of values.yaml
  • The templates and helpers
  • Dependency management
  • Packaging and distribution

Next step​

In the next chapter, we will dive deeper into Templates and Values.

→ Next chapter: Templates and Values

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