ArgoCD

ArgoCD is an open-source declarative continuous-delivery tool for Kubernetes that runs inside the cluster and applies manifests from a Git repository. It is the most widely deployed GitOps controller in the Kubernetes ecosystem.

How it works

An Application object in ArgoCD points at a Git repo, a path inside it, and a target cluster and namespace. ArgoCD continuously compares the manifests in Git (rendered via Helm, Kustomize, plain YAML, or Jsonnet) against the running cluster state. When they differ, ArgoCD shows the diff and applies it, either automatically (sync policy) or after a human clicks "Sync".

Common features

• App-of-Apps and ApplicationSets. Pattern for managing dozens or hundreds of applications from a single root Application.
• Sync waves and hooks. Order resource application; run pre-sync and post-sync hooks (database migrations, smoke tests).
• Multi-cluster. One ArgoCD instance can deploy to many target clusters.
• RBAC and SSO. Tied into the organization's identity provider; per-project access control.
• Web UI and CLI. Visualises the live application graph and sync status.

Ecosystem

• Argo Rollouts. Companion controller for canary and blue-green deployment strategies.
• Argo Workflows. Kubernetes-native workflow engine, often used as CI.
• Argo Events. Event-driven dependency manager for workflows.