Packaging Apps with Helm and Kustomize

hello/
├── base/
│   ├── deployment.yaml        # the Deployment from module 03
│   ├── service.yaml
│   └── kustomization.yaml
└── overlays/
    ├── dev/
    │   └── kustomization.yaml
    └── prod/
        └── kustomization.yaml

# base/kustomization.yaml: which files make up the app
apiVersion: kustomize.config.k8s.io/v1beta1
kind: Kustomization
resources:
  - deployment.yaml
  - service.yaml

# overlays/prod/kustomization.yaml: only what's different in Production
apiVersion: kustomize.config.k8s.io/v1beta1
kind: Kustomization
resources:
  - ../../base
namespace: shop-prod
images:
  - name: nginx
    newTag: "1.27.2"           # pin an exact version in Production
patches:
  - target:
      kind: Deployment
      name: hello
    patch: |-
      - op: replace
        path: /spec/replicas
        value: 4

# overlays/dev/kustomization.yaml: the base as it is, in its own namespace
apiVersion: kustomize.config.k8s.io/v1beta1
kind: Kustomization
resources:
  - ../../base
namespace: shop-dev

# Print the final YAML for an environment, without applying it
kubectl kustomize overlays/prod

# Apply an environment (-k instead of -f)
kubectl create namespace shop-prod
kubectl apply -k overlays/prod

# Inside a chart: templates/deployment.yaml (an excerpt)
spec:
  replicas: {{ .Values.replicaCount }}
  template:
    spec:
      containers:
        - name: {{ .Chart.Name }}
          image: "{{ .Values.image.repository }}:{{ .Values.image.tag }}"

# my-values.yaml: your settings, overriding the chart's defaults
replicaCount: 2

# Add a chart repository and look at what it offers
helm repo add podinfo https://stefanprodan.github.io/podinfo
helm repo update
helm search repo podinfo --versions | head

# See every setting the chart supports
helm show values podinfo/podinfo

# Install a specific version, with your values
helm install my-podinfo podinfo/podinfo --version <chart-version> -f my-values.yaml

# Change a setting, see the release history, roll back, and uninstall
helm upgrade my-podinfo podinfo/podinfo --version <chart-version> --set replicaCount=3
helm history my-podinfo
helm rollback my-podinfo 1
helm uninstall my-podinfo

# Render the YAML without installing, to review what a chart will create
helm template my-podinfo podinfo/podinfo -f my-values.yaml

# Build the hello/ folder above, reusing deployment.yaml and service.yaml
# from module 03, then compare the two environments
kubectl kustomize hello/overlays/dev
kubectl kustomize hello/overlays/prod

# Apply both side by side on kind
kubectl create namespace shop-dev
kubectl create namespace shop-prod
kubectl apply -k hello/overlays/dev
kubectl apply -k hello/overlays/prod
kubectl get deployments -A -l app=hello

# Clean up
kubectl delete -k hello/overlays/dev
kubectl delete -k hello/overlays/prod