KUBERNETES: TỪ CƠ BẢN ĐẾN NÂNG CAO

Module 8: Helm, Operators & GitOps

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🎯 Mục tiêu bài thực hành

• Tạo Helm chart từ đầu và install
• Tạo Helm hooks và tests
• Cài cert-manager operator và tạo TLS certificate
• Deploy ArgoCD và tạo Application
• Setup App of Apps pattern

Lab 1: Tạo Helm Chart

kubectl create namespace lab8
Tạo chart mới
helm create webapp
ls webapp/
Chart.yaml  charts/  templates/  values.yaml
Xem chart structure
cat webapp/Chart.yaml
cat webapp/values.yaml
Chỉnh sửa values.yaml
cat > webapp/values.yaml <<EOF
replicaCount: 2
image:
repository: nginx
tag: "1.27"
pullPolicy: IfNotPresent
service:
type: ClusterIP
port: 80
ingress:
enabled: false
resources:
requests:
cpu: "100m"
memory: "128Mi"
limits:
cpu: "500m"
memory: "256Mi"
livenessProbe:
httpGet:
path: /
port: http
readinessProbe:
httpGet:
path: /
port: http
EOF
Lint chart
helm lint webapp/
Dry run
helm install --dry-run --debug webapp-test webapp/ -n lab8
Install
helm install webapp webapp/ -n lab8
helm list -n lab8
Upgrade (thay đổi replicas)
helm upgrade webapp webapp/ -n lab8 --set replicaCount=3
Xem history
helm history webapp -n lab8
Rollback về revision 1
helm rollback webapp 1 -n lab8

Lab 2: Helm Hooks

# Thêm pre-upgrade hook (database migration giả lập)
cat > webapp/templates/migration-job.yaml <<EOF
apiVersion: batch/v1
kind: Job
metadata:
  name: "{{ .Release.Name }}-migration"
  annotations:
    "helm.sh/hook": pre-upgrade,pre-install
    "helm.sh/hook-weight": "-5"
    "helm.sh/hook-delete-policy": hook-succeeded
spec:
  template:
    spec:
      restartPolicy: Never
      containers:
      - name: migration
        image: busybox:1.36
        command: ['sh', '-c', 'echo "Running DB migration..."; sleep 3; echo "Migration complete!"']
EOF
Upgrade với hook
helm upgrade webapp webapp/ -n lab8
Xem migration job
kubectl get jobs -n lab8
kubectl logs -n lab8 job/webapp-migration

Lab 3: Helm Tests

# Tạo test
mkdir -p webapp/templates/tests
cat > webapp/templates/tests/test-connection.yaml <<EOF
apiVersion: v1
kind: Pod
metadata:
  name: "{{ .Release.Name }}-test-connection"
  annotations:
    "helm.sh/hook": test
spec:
  restartPolicy: Never
  containers:
  - name: test
    image: busybox:1.36
    command:
    - sh
    - -c
    - |
      until wget -qO- http://{{ .Release.Name }}-webapp:{{ .Values.service.port }}; do
        echo "Waiting for service..."
        sleep 2
      done
      echo "Test passed!"
EOF
helm upgrade webapp webapp/ -n lab8
helm test webapp -n lab8

Lab 4: cert-manager Operator

# Cài cert-manager
helm repo add jetstack https://charts.jetstack.io
helm repo update
helm install cert-manager jetstack/cert-manager \
  --namespace cert-manager \
  --create-namespace \
  --set crds.enabled=true
kubectl get pods -n cert-manager
cert-manager-xxx, cert-manager-cainjector-xxx, cert-manager-webhook-xxx
Tạo self-signed ClusterIssuer
cat <<EOF | kubectl apply -f -
apiVersion: cert-manager.io/v1
kind: ClusterIssuer
metadata:
name: selfsigned-issuer
spec:
selfSigned: {}
Certificate cho webapp
apiVersion: cert-manager.io/v1
kind: Certificate
metadata:
name: webapp-tls
namespace: lab8
spec:
secretName: webapp-tls-secret
issuerRef:
name: selfsigned-issuer
kind: ClusterIssuer
dnsNames:

webapp.lab8.svc.cluster.local
webapp.example.com
duration: 2160h    # 90 days
renewBefore: 360h  # renew khi còn 15 days
EOF

Xem certificate status
kubectl get certificate -n lab8
kubectl describe certificate webapp-tls -n lab8
Status: Ready
Xem generated secret
kubectl get secret webapp-tls-secret -n lab8
kubectl get secret webapp-tls-secret -n lab8 -o jsonpath='{.data.tls.crt}' | base64 -d | openssl x509 -text -noout

Lab 5: Deploy ArgoCD

# Cài ArgoCD
kubectl create namespace argocd
kubectl apply -n argocd -f https://raw.githubusercontent.com/argoproj/argo-cd/stable/manifests/install.yaml
Chờ ArgoCD ready
kubectl wait --for=condition=available deployment/argocd-server -n argocd --timeout=120s
Lấy admin password
ARGOCD_PASSWORD=$(kubectl -n argocd get secret argocd-initial-admin-secret 

-o jsonpath="{.data.password}" | base64 -d)
echo "ArgoCD password: $ARGOCD_PASSWORD"
Port-forward UI
kubectl port-forward svc/argocd-server -n argocd 8080:443 &
echo "ArgoCD UI: https://localhost:8080 (admin/$ARGOCD_PASSWORD)"
Hoặc dùng ArgoCD CLI
argocd login localhost:8080 --username admin --password $ARGOCD_PASSWORD --insecure

Lab 6: Tạo ArgoCD Application

# Tạo Application bằng CLI
argocd app create webapp-gitops \
  --repo https://github.com/argoproj/argocd-example-apps \
  --path guestbook \
  --dest-server https://kubernetes.default.svc \
  --dest-namespace lab8 \
  --sync-policy automated \
  --auto-prune \
  --self-heal
Xem status
argocd app list
argocd app get webapp-gitops
Sync thủ công
argocd app sync webapp-gitops
Xem trong browser: https://localhost:8080

# Tạo Application bằng YAML
cat <<EOF | kubectl apply -f -
apiVersion: argoproj.io/v1alpha1
kind: Application
metadata:
  name: guestbook
  namespace: argocd
spec:
  project: default
  source:
    repoURL: https://github.com/argoproj/argocd-example-apps
    targetRevision: HEAD
    path: guestbook
  destination:
    server: https://kubernetes.default.svc
    namespace: lab8
  syncPolicy:
    automated:
      prune: true
      selfHeal: true
    syncOptions:
    - CreateNamespace=true
EOF

Lab 7: App of Apps

# Tạo cấu trúc Git repo (simulate locally)
mkdir -p /tmp/gitops-demo/apps-of-apps
mkdir -p /tmp/gitops-demo/apps/{webapp,monitoring}
Root Application file
cat > /tmp/gitops-demo/apps-of-apps/webapp.yaml <<EOF
apiVersion: argoproj.io/v1alpha1
kind: Application
metadata:
name: webapp-child
namespace: argocd
spec:
project: default
source:
repoURL: https://github.com/argoproj/argocd-example-apps
path: helm-guestbook
targetRevision: HEAD
destination:
server: https://kubernetes.default.svc
namespace: lab8
syncPolicy:
automated:
prune: true
selfHeal: true
EOF
Apply root app
kubectl apply -f /tmp/gitops-demo/apps-of-apps/ -n argocd
ArgoCD sẽ tìm và deploy tất cả Application CRDs trong thư mục
argocd app list

Lab 8: Simulate GitOps Workflow

# 1. Xem app đang chạy
kubectl get pods -n lab8
2. Simulate: ai đó thay đổi trực tiếp trong cluster (drift)
kubectl scale deployment guestbook-ui -n lab8 --replicas=0
3. ArgoCD detect và tự heal trong vài phút
kubectl get pods -n lab8 -w
4. Xem ArgoCD phục hồi về 2 replicas (self-heal)
argocd app get guestbook
5. Xem sync history
argocd app history guestbook

Cleanup

helm uninstall webapp -n lab8
kubectl delete namespace lab8
kubectl delete application guestbook webapp-gitops webapp-child -n argocd
kubectl delete namespace argocd
helm uninstall cert-manager -n cert-manager
kubectl delete namespace cert-manager

Tổng kết

• ✅ Helm chart từ đầu: structure, templates, values
• ✅ Helm hooks: pre-upgrade migration job
• ✅ Helm tests: verify deployment
• ✅ cert-manager: tự động TLS certificates
• ✅ ArgoCD: Application + sync policy automated
• ✅ App of Apps: quản lý nhiều apps bằng 1 root app
• ✅ GitOps self-healing: ArgoCD tự sửa drift