ArgoCD

ArgoCD is the industry standard for GitOps. It syncs the state of a Kubernetes cluster with a Git repository. 2025 features: ApplicationSets for multi-tenant management.

When to Use

• Kubernetes CD: Continuous Delivery specifically for K8s.
• GitOps: You want your cluster state (YAML) versioned in Git.
• Drift Detection: ArgoCD alerts you if someone manually hacks kubectl edit in production.

Quick Start

# Application.yaml
apiVersion: argoproj.io/v1alpha1
kind: Application
metadata:
  name: guestbook
  namespace: argocd
spec:
  project: default
  source:
    repoURL: https://github.com/argoproj/argocd-example-apps.git
    targetRevision: HEAD
    path: guestbook
  destination:
    server: https://kubernetes.default.svc
    namespace: guestbook

Core Concepts

Application

The link between a Git source and a K8s destination.

ApplicationSet

A generator that spawns multiple Application resources. Example: "Deploy every folder in this repo as an app" or "Deploy this app to every cluster".

Sync Phases

Pre-Sync (Schema migration), Sync (Deployment), Post-Sync (Health check).

Best Practices (2025)

Do:

• Use ApplicationSets: The modern way to manage many apps.
• Separate Config from Code: Keep app source code and K8s manifests in separate repos or at least separate folders.
• Use "App of Apps": A bootstrap pattern where one root Argo app deploys all other apps.

Don't:

• Don't manage Secrets in plain Git: Use Sealed Secrets, External Secrets Operator, or ArgoCD Vault Plugin.

References

• ArgoCD Documentation