ArgoCD

What is ArgoCD?

ArgoCD is a declarative GitOps continuous delivery tool for Kubernetes that automatically syncs applications from Git repositories.

Installation

# Install ArgoCD
kubectl create namespace argocd
kubectl apply -n argocd -f https://raw.githubusercontent.com/argoproj/argo-cd/stable/manifests/install.yaml

# Access ArgoCD UI
kubectl port-forward svc/argocd-server -n argocd 8080:443

# Get admin password
kubectl -n argocd get secret argocd-initial-admin-secret -o jsonpath="{.data.password}" | base64 -d

Application Definition

apiVersion: argoproj.io/v1alpha1
kind: Application
metadata:
  name: myapp
  namespace: argocd
spec:
  project: default
  source:
    repoURL: https://github.com/myorg/myapp
    targetRevision: main
    path: k8s
  destination:
    server: https://kubernetes.default.svc
    namespace: production
  syncPolicy:
    automated:
      prune: true
      selfHeal: true
      allowEmpty: false
    syncOptions:
      - CreateNamespace=true

Multi-Stack Application

# Angular Frontend
apiVersion: argoproj.io/v1alpha1
kind: Application
metadata:
  name: frontend
  namespace: argocd
spec:
  project: default
  source:
    repoURL: https://github.com/myorg/myapp
    targetRevision: main
    path: k8s/frontend
  destination:
    server: https://kubernetes.default.svc
    namespace: production
  syncPolicy:
    automated:
      prune: true
      selfHeal: true

---
# .NET API
apiVersion: argoproj.io/v1alpha1
kind: Application
metadata:
  name: api
  namespace: argocd
spec:
  project: default
  source:
    repoURL: https://github.com/myorg/myapp
    targetRevision: main
    path: k8s/api
  destination:
    server: https://kubernetes.default.svc
    namespace: production
  syncPolicy:
    automated:
      prune: true
      selfHeal: true

---
# Node.js Service
apiVersion: argoproj.io/v1alpha1
kind: Application
metadata:
  name: service
  namespace: argocd
spec:
  project: default
  source:
    repoURL: https://github.com/myorg/myapp
    targetRevision: main
    path: k8s/service
  destination:
    server: https://kubernetes.default.svc
    namespace: production
  syncPolicy:
    automated:
      prune: true
      selfHeal: true

Helm Integration

apiVersion: argoproj.io/v1alpha1
kind: Application
metadata:
  name: myapp
  namespace: argocd
spec:
  project: default
  source:
    repoURL: https://github.com/myorg/myapp
    targetRevision: main
    path: helm/myapp
    helm:
      valueFiles:
        - values-production.yaml
      parameters:
        - name: api.replicaCount
          value: "10"
        - name: frontend.image.tag
          value: "v1.0.0"
  destination:
    server: https://kubernetes.default.svc
    namespace: production
  syncPolicy:
    automated:
      prune: true
      selfHeal: true

App of Apps Pattern

# Root application
apiVersion: argoproj.io/v1alpha1
kind: Application
metadata:
  name: root-app
  namespace: argocd
spec:
  project: default
  source:
    repoURL: https://github.com/myorg/myapp
    targetRevision: main
    path: argocd/apps
  destination:
    server: https://kubernetes.default.svc
    namespace: argocd
  syncPolicy:
    automated:
      prune: true
      selfHeal: true

# argocd/apps/frontend.yaml
apiVersion: argoproj.io/v1alpha1
kind: Application
metadata:
  name: frontend
spec:
  source:
    repoURL: https://github.com/myorg/myapp
    path: k8s/frontend
  destination:
    namespace: production

Environment Promotion

# Development
apiVersion: argoproj.io/v1alpha1
kind: Application
metadata:
  name: myapp-dev
spec:
  source:
    repoURL: https://github.com/myorg/myapp
    targetRevision: develop
    path: k8s/overlays/dev
  destination:
    namespace: dev

---
# Staging
apiVersion: argoproj.io/v1alpha1
kind: Application
metadata:
  name: myapp-staging
spec:
  source:
    repoURL: https://github.com/myorg/myapp
    targetRevision: main
    path: k8s/overlays/staging
  destination:
    namespace: staging

---
# Production
apiVersion: argoproj.io/v1alpha1
kind: Application
metadata:
  name: myapp-prod
spec:
  source:
    repoURL: https://github.com/myorg/myapp
    targetRevision: v1.0.0
    path: k8s/overlays/production
  destination:
    namespace: production
  syncPolicy:
    automated:
      prune: false  # Manual approval for production
      selfHeal: false

CLI Commands

# Login
argocd login localhost:8080

# Create application
argocd app create myapp \
  --repo https://github.com/myorg/myapp \
  --path k8s \
  --dest-server https://kubernetes.default.svc \
  --dest-namespace production

# Sync application
argocd app sync myapp

# Get application status
argocd app get myapp

# List applications
argocd app list

# Delete application
argocd app delete myapp

Sync Waves

apiVersion: apps/v1
kind: Deployment
metadata:
  name: database
  annotations:
    argocd.argoproj.io/sync-wave: "0"  # Deploy first

---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: api
  annotations:
    argocd.argoproj.io/sync-wave: "1"  # Deploy second

---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: frontend
  annotations:
    argocd.argoproj.io/sync-wave: "2"  # Deploy last

Health Checks

apiVersion: argoproj.io/v1alpha1
kind: Application
metadata:
  name: myapp
spec:
  source:
    repoURL: https://github.com/myorg/myapp
    path: k8s
  destination:
    namespace: production
  syncPolicy:
    automated:
      prune: true
      selfHeal: true
    retry:
      limit: 5
      backoff:
        duration: 5s
        factor: 2
        maxDuration: 3m

Notifications

apiVersion: v1
kind: ConfigMap
metadata:
  name: argocd-notifications-cm
  namespace: argocd
data:
  service.slack: |
    token: $slack-token
  trigger.on-deployed: |
    - when: app.status.operationState.phase in ['Succeeded']
      send: [app-deployed]
  template.app-deployed: |
    message: |
      Application {{.app.metadata.name}} deployed successfully!
    slack:
      attachments: |
        [{
          "title": "{{.app.metadata.name}}",
          "color": "good"
        }]

Interview Tips

• Explain ArgoCD: GitOps CD tool for Kubernetes
• Show applications: Multi-stack deployment
• Demonstrate Helm: Integration with Helm charts
• Discuss sync: Automated vs manual
• Mention environments: Dev, staging, production
• Show CLI: Common commands

Summary

ArgoCD automates Kubernetes deployments using GitOps principles. Define applications declaratively pointing to Git repositories. Supports Helm charts and Kustomize. Implements automated sync with self-healing. Use app-of-apps pattern for complex deployments. Provides environment promotion and sync waves. Essential for GitOps-based Kubernetes deployments.