Helm: Packaging Kubernetes Applications

helm repo add ingress-nginx https://kubernetes.github.io/ingress-nginx
helm upgrade --install ingress-nginx ingress-nginx/ingress-nginx \
  -n ingress-nginx --create-namespace --version 4.11.3 -f values/ingress-prod.yaml
helm list -A
helm history api -n petpal
helm rollback api 4 -n petpal
helm template api ./charts/api -f values/prod.yaml   # render locally, no cluster
helm diff upgrade api ./charts/api -f values/prod.yaml   # (helm-diff plugin)

charts/api/
├── Chart.yaml            # name, version (chart), appVersion, dependencies
├── values.yaml           # defaults
├── values.schema.json    # optional JSON Schema validation of values
├── templates/
│   ├── _helpers.tpl      # named templates (labels, names)
│   ├── deployment.yaml
│   ├── service.yaml
│   ├── ingress.yaml
│   ├── hpa.yaml
│   ├── NOTES.txt         # printed after install
│   └── tests/test-connection.yaml
└── charts/               # vendored dependencies

# Chart.yaml
apiVersion: v2
name: api
version: 1.8.0          # chart version — bump on every chart change
appVersion: "1.4.2"     # version of the app it deploys
dependencies:
  - name: redis
    version: 20.x.x
    repository: oci://registry-1.docker.io/bitnamicharts
    condition: redis.enabled

# templates/deployment.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
  name: {{ include "api.fullname" . }}
  labels: {{- include "api.labels" . | nindent 4 }}
spec:
  {{- if not .Values.autoscaling.enabled }}
  replicas: {{ .Values.replicaCount }}
  {{- end }}
  selector:
    matchLabels: {{- include "api.selectorLabels" . | nindent 6 }}
  template:
    metadata:
      labels: {{- include "api.selectorLabels" . | nindent 8 }}
      annotations:
        checksum/config: {{ include (print $.Template.BasePath "/configmap.yaml") . | sha256sum }}
    spec:
      containers:
        - name: api
          image: "{{ .Values.image.repository }}:{{ .Values.image.tag | default .Chart.AppVersion }}"
          resources: {{- toYaml .Values.resources | nindent 12 }}
          {{- with .Values.env }}
          env:
            {{- range $k, $v := . }}
            - name: {{ $k }}
              value: {{ $v | quote }}
            {{- end }}
          {{- end }}

# values.yaml
replicaCount: 2
image: { repository: ghcr.io/petpal/api, tag: "" }
resources: { requests: { cpu: 250m, memory: 256Mi }, limits: { memory: 512Mi } }
autoscaling: { enabled: false, minReplicas: 2, maxReplicas: 10, targetCPU: 65 }
ingress: { enabled: false, host: "" }
env: { LOG_LEVEL: info }