How does ArgoCD detect and reconcile drift between Git and the cluster?
CI/CD & GitOps · Intermediate level
Answer
Argo CD detects drift by rendering the configured source, reading live Kubernetes objects, comparing desired versus actual state, and marking the application OutOfSync when they differ. With automated sync or self-heal enabled, it can apply Git state back to the cluster.
Technical explanation
Drift can be intentional during emergency response, but it should be time-bound and reconciled back into Git.
Self-heal is powerful, but it can fight other controllers if ownership boundaries are unclear.
GitOps separates build from deploy: CI produces immutable artifacts, while the GitOps controller reconciles declarative desired state into the cluster.
Argo CD status has two dimensions: sync status indicates desired versus live state; health status indicates whether live resources appear operationally healthy.
Use projects, RBAC, repository allowlists, destination restrictions, sync windows, and admission policies to constrain what an Application may deploy.
Prefer reviewed Git changes over direct kubectl changes; direct changes create drift and bypass audit, policy, and promotion workflow.
Hands-on example
1. Model the desired state for: How does ArgoCD detect and reconcile drift between Git and the cluster in a GitOps repository, for example environments/staging/apps/payments and environments/prod/apps/payments.
2. Create an Argo CD Application that points to repoURL, targetRevision, path or chart, destination server, namespace, and project; render with Helm/Kustomize before merging.
3. Open a pull request that changes only the desired version or values, require review and policy checks, then merge to let Argo CD detect OutOfSync state.
4. Run argocd app get payments and argocd app diff payments, then sync manually or let automated sync reconcile; verify sync status, health status, events, and Kubernetes rollout status.
5. Test rollback by reverting the Git commit or promoting the previous artifact digest, then watch Argo CD reconcile the cluster back to the known-good desired state.
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