What is ArgoCD and how does it implement GitOps for Kubernetes deployments?

ArgoCD is a declarative, GitOps continuous delivery tool for Kubernetes that synchronizes application state from Git repositories to Kubernetes clusters.

How ArgoCD Works

ArgoCD follows the GitOps principle: Git is the single source of truth for application definitions. It continuously monitors Git repositories and Kubernetes clusters, reconciling any differences.

Core Workflow

1. Developer commits Kubernetes manifests (or Helm charts) to Git
2. ArgoCD detects the change in the Git repository
3. ArgoCD compares desired state (Git) vs actual state (cluster)
4. ArgoCD syncs the cluster to match Git (automatically or with approval)

Key Concepts

Application

An Application represents a deployed instance of your Kubernetes workload.

apiVersion: argoproj.io/v1alpha1
kind: Application
metadata:
  name: my-app
spec:
  source:
    repoURL: https://github.com/org/app-gitops
    targetRevision: HEAD
    path: k8s/production
  destination:
    server: https://kubernetes.default.svc
    namespace: production
  syncPolicy:
    automated:
      prune: true
      selfHeal: true

Sync Policies

• Manual: Requires human approval for each sync
• Automated: Automatically syncs when drift is detected
• prune: Deletes resources removed from Git
• selfHeal: Reverts manual changes to the cluster

App of Apps Pattern

A parent Application manages child Applications, enabling management of multiple applications across environments.

ArgoCD vs Traditional CI/CD

Multi-cluster Management

ArgoCD can manage multiple Kubernetes clusters from a single control plane:

• Register external clusters as ArgoCD destinations
• Deploy the same application across dev/staging/prod clusters
• Use ApplicationSets for templated multi-cluster deployments

Integration with CI

Typical pattern:

1. CI (GitHub Actions, Jenkins) builds, tests, and pushes Docker image
2. CI updates image tag in the GitOps repository
3. ArgoCD detects the change and deploys to Kubernetes