EN_CS_GitOps - somaz94/DevOps-Engineer GitHub Wiki

Q8: What is GitOps?

Question: Explain GitOps core principles and how ArgoCD automates Kubernetes deployments. Focus on the Declarative approach and the Reconciliation Loop.


Key Terms

Term Description
GitOps Operational model using Git as the Single Source of Truth
Declarative Define what the desired state is (not how to get there)
Imperative Issue commands to reach a state step by step
Reconciliation Process of making actual state match desired state
ArgoCD Kubernetes-native GitOps CD tool
Flux CNCF Graduated GitOps tool
Sync Applying Git state to the cluster
Self-heal Auto-restoring Git state when manual changes are detected

GitOps 4 Core Principles

Principle Description
Declarative System desired state is declared, not commanded
Versioned & Immutable All changes tracked in Git; rollback anytime
Pulled Automatically Agent continuously monitors Git; auto-deploys on change
Continuously Reconciled Detects drift between actual and desired state; auto-corrects

Traditional CI/CD vs GitOps

Traditional CI/CD:
Git Commit → CI Build → kubectl apply → Kubernetes
Problem: requires kubectl access, Git and live state can diverge

GitOps (ArgoCD):
Git Commit → CI Build → Container Registry
     ↓
Git Manifest Repo ← ArgoCD polling → Kubernetes auto-sync
Benefit: only Git access needed; Git always = live state

Reconciliation Loop

1. Observe  → Read Desired State from Git (replicas: 3)
     ↓
2. Diff     → Read Actual State from Kubernetes (running: 2)
             Desired ≠ Actual → Out of Sync
     ↓
3. Act      → Run kubectl apply, create 1 Pod
     ↓
4. Verify   → Re-check state (running: 3) → Synced
     ↓
     Repeat (every 3 minutes by default)

ArgoCD Application Definition

apiVersion: argoproj.io/v1alpha1
kind: Application
metadata:
  name: my-app
  namespace: argocd
spec:
  source:
    repoURL: https://github.com/example/my-app.git
    targetRevision: main
    path: k8s/overlays/production
  destination:
    server: https://kubernetes.default.svc
    namespace: production
  syncPolicy:
    automated:
      prune: true       # Remove resources deleted from Git
      selfHeal: true    # Auto-revert manual changes
    syncOptions:
    - CreateNamespace=true
    retry:
      limit: 5
      backoff:
        duration: 5s
        factor: 2
        maxDuration: 3m

Deployment Workflow

# 1. Commit image tag change to Git
git commit -m "Update app to v2.0.0"
git push origin main

# 2. ArgoCD detects change (polling or webhook)
# 3. Preview diff
argocd app diff my-app

# 4. Auto or manual sync
argocd app sync my-app

# 5. Rollback (Git revert → ArgoCD auto-restores)
git revert HEAD && git push origin main

ArgoCD vs Flux

Feature ArgoCD Flux
UI Rich Web UI CLI-focused
Sync Method Pull (every 3min default) Push + Pull
Helm Support Native Helm Controller
Image Auto-update Image Updater (separate) Built-in (Image Automation)
CNCF Status Incubating Graduated

GitOps Benefits Summary

Area Benefit
Security No direct Kubernetes access needed; controlled via Git permissions
Reliability Declarative consistency, self-healing, easy rollback via git revert
Visibility Web UI for full state, diff preview, real-time health monitoring
Collaboration Git-based code review, PR-based deploy approval, full audit trail

Reference

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