ArgoCD Learning Project

A simple project to learn ArgoCD GitOps with a frontend webserver and backend API.

Project Structure

argo/
├── argocd/                    # ArgoCD Application manifests
│   ├── app-of-apps.yaml       # Parent app that manages other apps
│   ├── application-backend.yaml
│   ├── application-frontend.yaml
│   ├── namespace.yaml
│   └── project.yaml           # ArgoCD Project definition
├── base/
│   ├── backend/               # Backend API (http-echo)
│   │   ├── deployment.yaml
│   │   ├── service.yaml
│   │   └── kustomization.yaml
│   └── frontend/              # Frontend webserver (nginx)
│       ├── configmap.yaml
│       ├── deployment.yaml
│       ├── service.yaml
│       └── kustomization.yaml
└── README.md

Prerequisites

• Kubernetes cluster (minikube, kind, k3s, etc.)
• kubectl configured
• ArgoCD installed in your cluster

Quick Start

1. Install ArgoCD (if not already installed)

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

2. Access ArgoCD UI

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

# Port forward to access the UI
kubectl port-forward svc/argocd-server -n argocd 8080:443

Then open https://localhost:8080 (username: admin)

3. Push this repo to GitHub

git init
git add .
git commit -m "Initial ArgoCD demo project"
git remote add origin https://github.com/YOUR_USERNAME/argo.git
git push -u origin main

4. Update the repo URL

Edit these files and replace YOUR_USERNAME with your GitHub username:

• argocd/application-backend.yaml
• argocd/application-frontend.yaml
• argocd/app-of-apps.yaml

5. Deploy using App of Apps pattern

kubectl apply -f argocd/app-of-apps.yaml

Or deploy apps individually:

kubectl apply -f argocd/namespace.yaml
kubectl apply -f argocd/project.yaml
kubectl apply -f argocd/application-backend.yaml
kubectl apply -f argocd/application-frontend.yaml

6. Access the frontend

# If using minikube
minikube service frontend -n demo-app

# Or port-forward
kubectl port-forward svc/frontend -n demo-app 8081:80

Learning Exercises

Exercise 1: Manual Sync

1. Disable auto-sync in the ArgoCD UI
2. Change replicas: 2 to replicas: 3 in base/backend/deployment.yaml
3. Push the change to git
4. Watch ArgoCD detect the change (OutOfSync status)
5. Click "Sync" to apply the change

Exercise 2: Self-Healing

1. Manually scale the backend: kubectl scale deployment backend -n demo-app --replicas=1
2. Watch ArgoCD automatically restore to the desired state (2 replicas)

Exercise 3: Rollback

1. Make a change to the frontend ConfigMap
2. Push to git and let it sync
3. Use ArgoCD UI to rollback to a previous version

Exercise 4: Add a new application

1. Create a new directory base/redis/
2. Add Redis deployment manifests
3. Create argocd/application-redis.yaml
4. Push and watch ArgoCD deploy it automatically

Key Concepts

Concept	Description
Application	A group of Kubernetes resources defined in a Git repo
Project	A logical grouping of Applications with access controls
Sync	Process of applying Git manifests to the cluster
Self-Heal	Automatically revert manual changes to match Git
Prune	Delete resources removed from Git
App of Apps	Pattern where one Application manages other Applications

Useful Commands

# ArgoCD CLI (install: brew install argocd)
argocd login localhost:8080
argocd app list
argocd app get frontend
argocd app sync frontend
argocd app history frontend
argocd app rollback frontend <revision>

# Kubectl
kubectl get applications -n argocd
kubectl get all -n demo-app

Troubleshooting

App stuck in "Progressing":

kubectl describe application frontend -n argocd
kubectl get events -n demo-app

Sync failed:

• Check the ArgoCD UI for detailed error messages
• Verify the Git repo URL and branch are correct
• Ensure the path to manifests exists