ArgoCD App Health Checker

ArgoCD is a declarative, GitOps continuous delivery tool for Kubernetes. It monitors a Git repository (the source of truth) and automatically syncs the cluster state to match what's defined in Git. ArgoCD supports Helm charts, Kustomize, plain YAML, and other templating tools. It provides a web UI and CLI to visualize application health, sync status, and drift between Git and the live cluster.

GitOps is an operational model where Git is the single source of truth for infrastructure and application configuration. All changes go through Git (pull requests, reviews), and automation syncs the cluster to match. Benefits: full audit trail of every change, easy rollback (git revert), consistent environments, and reduced manual kubectl access. ArgoCD implements GitOps by continuously reconciling the cluster with the Git repository state.

Without automated sync, ArgoCD detects drift between Git and the cluster but requires a manual sync (via UI or CLI). With 'automated: {}', ArgoCD automatically applies changes when it detects the Git state has changed. The 'prune: true' option tells ArgoCD to delete resources that have been removed from Git. The 'selfHeal: true' option tells ArgoCD to revert manual changes made directly to the cluster, ensuring Git remains the only source of truth.

Synced means the live cluster state matches what's defined in Git. Healthy means the deployed resources are running correctly (Pods are running, Deployments have expected replicas, etc.). An application can be Synced but Unhealthy (e.g. all manifests applied but Pods are CrashLooping). It can also be OutOfSync but Healthy (manual changes made to a running app). Aim for both Synced and Healthy.

targetRevision: HEAD tracks the tip of the default branch and auto-syncs with every commit. For production environments, pin to a specific tag or commit SHA for controlled, auditable deployments. For staging/dev environments, HEAD can be acceptable. Many teams use a promotion model: tag releases in Git and update the ArgoCD Application's targetRevision as part of the release process, maintaining a clear history of exactly what was deployed.

An AppProject scopes what ArgoCD Applications are allowed to do: which source repositories they can use, which destination clusters and namespaces they can deploy to, and which resource types are allowed or denied. The 'default' project permits everything. For multi-team environments, create dedicated AppProjects with RBAC policies so team A cannot accidentally (or maliciously) deploy to team B's namespace. AppProjects are the primary access control mechanism in ArgoCD.