Helm
====
A Helm Chart is like a "package" of templates for Kubernetes applications.
Chart Components:
my-app-chart/
├── Chart.yaml          # Metadata (name, version, description)
├── values.yaml         # Default configuration values
├── templates/          # Kubernetes manifest templates
│   ├── deployment.yaml
│   ├── service.yaml
│   └── ingress.yaml
└── charts/             # Sub-charts/dependencies


1. Download helm. All the releases can be found in https://github.com/helm/helm/releases
wget https://get.helm.sh/helm-v3.19.0-linux-amd64.tar.gz
tar -xvf helm-v3.19.0-linux-amd64.tar.gz
sudo cp linux-amd64/helm /usr/local/bin/helm

2. A helm Chart is a collection of files to deploy an application. You can browse for the available charts in https://artifacthub.io/packages/search. Let's search in the helm hub for ingress.
helm search hub ingress

3. We will be using a simple nginx ingress controller. The official NGINX ingress URL is https://kubernetes.github.io/ingress-nginx
helm repo add ingress-nginx https://kubernetes.github.io/ingress-nginx
helm repo list

4. Update the helm repo. This will download the latest charts.
helm repo update

If using Cloud Services:
	5. Download and edit the values.yaml file. The default configuration provided uses a Deployment. We will configure an ingress controller on every node to handle traffic.
	helm fetch ingress-nginx/ingress-nginx --untar
	cd ingress-nginx
	vi values.yaml
	kind: DaemonSet		# change from Deployment to DaemonSet
	
	6. Install the controller using the chart from current directory.
	helm install myingress .
	
	7. Wait for the ingress controller to come up before moving to the next step.
If using Local VM:
5. List charts that have been downloaded for repo ingress-nginx
helm search repo ingress-nginx/
helm search repo nginx		# search for nginx related charts

6. Show detailed information for a specific chart. Use helm show chart|values|all repo/chart
helm show chart ingress-nginx/ingress-nginx
helm show values ingress-nginx/ingress-nginx
helm show all ingress-nginx/ingress-nginx

7. Install the chart by using a file or ad-hoc.
cat <<EOF > nginx-hostnet.yaml
controller:
  hostNetwork: true       # Bind directly to host ports
  hostPort:
    enabled: true         # Open ports on the host
  kind: DaemonSet        # Ensures one pod per node
  service:
    enabled: false        # Disable NodePort/LoadBalancer services
  ingressClassResource:
    enabled: true
    name: nginx
    default: true
  ingressClass: nginx
  watchIngressWithoutClass: false  # Only watch Ingresses with class: nginx

  publishService:
    enabled: false        # Disable publishing a Service
  extraArgs:
    publish-status-address: "0.0.0.0"  # Allow external status checks
EOF

helm upgrade -i ingress-nginx ingress-nginx/ingress-nginx \
	--namespace ingress-nginx \
	--create-namespace \
	-f nginx-hostnet.yaml

OR
	helm upgrade -i ingress-nginx ingres-nginx/ingress-nginx \
		--namespace ingress-nginx \
		--create-namespace \
		--set controller.hostNetwork=true \
		--set controller.hostPort.enabled=true \
		--set controller.kind=DaemonSet \
		--set controller.service.enabled=false ...

8. Check if you have any ingress in all namespace
kubeclt get ingress --all-namespaces

9. Create ingress for your web service (port 80) in the testing namespace.
kubectl create ingress -h
kubectl create ingress simple --class=nginx --rule="web.example.net/=web:80"
kubectl get ingress

10. Test your ingress.
curl -H "Host: web.example.net" http://master


Kustomize
=========
Kustomize is a configuration management tool built into kubectl that lets you customize Kubernetes YAML files — without needing to use templating languages (like Helm does).

Basic Structure:
my-app/
├── base/
│   ├── deployment.yaml
│   ├── service.yaml
│   └── kustomization.yaml
└── overlays/
    ├── dev/
    │   └── kustomization.yaml
    └── prod/
        └── kustomization.yaml

1. Create a base kustomization file and the resource files for your web application.
cd
mkdir -p web/{base,overlays/{dev,prod}}
tree web
cp deploy-web.yaml web/base/deployment.yaml
kubectl expose -f deploy-web.yaml --dry-run=client -o yaml > web/base/service.yaml
cat << EOF > web/base/kustomization.yaml
resources:
  - deployment.yaml
  - service.yaml
EOF

2. Create the development kustomization files.
cat << EOF >  web/overlays/dev/kustomization.yaml
resources:
  - ../../base

namePrefix: dev-
labels:
- includeSelectors: true
  pairs:
    environment: dev

patches:
  - target:
      kind: Deployment
      name: web
    patch: |
      - op: replace
        path: /spec/replicas
        value: 2
EOF

3. Populate the production directory
cat << EOF >  web/overlays/prod/kustomization.yaml
resources:
  - ../../base

patches:
  - path: prod-deploy.yaml
EOF

sed 's#image: nginx#image: quay.io/kelvinlai/myphp:port8080#' deploy-web.yaml > web/overlays/prod/prod-deploy.yaml

4. Create a dummy namespace and apply your kustomize file
kubectl create ns dummy
kubectl -n dummy apply -k web/overlays/dev
kubectl -n dummy get all

5. Try the production now.
kubectl -n dummy apply -k web/overlays/prod

6. This lab is intended to have the dev and prod create different names. In real life, we might not be using prefix, therefore the applications are upgraded in place. 

7. Clean up.
kubectl delete -k web/overlays/prod
kubectl delete -k web/overlays/dev
kubectl delete ns dummy