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Maven / ArgoCD interview questions

What is self-healing in ArgoCD and how do you enable it?

Self-healing in ArgoCD means that when the live cluster state drifts from the desired Git state — due to manual changes, operator mistakes, or other controllers modifying resources — ArgoCD automatically detects the drift and re-applies the Git state to bring the cluster back into sync, without any human intervention.

Self-healing is distinct from simply enabling automated sync. Automated sync fires when Git changes (a new commit is detected). Self-healing fires when the cluster changes while Git stays the same. Together they cover both directions of drift.

Enable self-healing in the Application's syncPolicy:

syncPolicy:
  automated:
    selfHeal: true
    prune: true       # also enable pruning if you want deleted Git resources removed

With selfHeal: true, the Application Controller compares live state against Git state every time a watch event fires from the Kubernetes API (near-real-time). When it detects OutOfSync, it immediately triggers a sync to restore the desired state.

A practical example: if an engineer runs kubectl scale deployment my-app --replicas=0 in production, ArgoCD with selfHeal enabled will detect the replica count change within seconds and restore replicas to the count defined in Git.

Self-healing should be combined with Sync Windows if you want to restrict when auto-corrections can occur (e.g., only during business hours or excluding a maintenance window).

What triggers ArgoCD's self-healing mechanism?
An engineer manually sets replicas to 0 on a Deployment managed by ArgoCD with selfHeal: true. What happens?

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What is ArgoCD and what problem does it solve? What is GitOps and how does ArgoCD implement it? What are the core components of ArgoCD? What is an ArgoCD Application and what fields does its manifest require? What are the different application sync statuses in ArgoCD? How do you install ArgoCD on a Kubernetes cluster? What is an ArgoCD Project and how does it differ from a Kubernetes namespace? How does ArgoCD support Helm charts? How does ArgoCD support Kustomize? What is self-healing in ArgoCD and how do you enable it? What is the difference between ArgoCD automated sync and self-healing? How does ArgoCD handle resource pruning and what risks does enabling it carry? What is the ArgoCD App of Apps pattern and when should you use it? How do ArgoCD Sync Waves and Sync Hooks work together to control deployment ordering? What is an ArgoCD ApplicationSet and how does the Git generator work? How does ArgoCD integrate with external secret management tools like Vault or Sealed Secrets? How do you configure ArgoCD RBAC and what are the built-in roles? What is ArgoCD Image Updater and how does it automate container image updates? How does ArgoCD manage multiple clusters and what are the methods for registering them? What are ArgoCD Sync Windows and how do you configure them? How does ArgoCD handle ignoreDifferences and when should you use it? What are ArgoCD resource health checks and how do you write a custom one? How does ArgoCD handle SSO and what identity providers does it support? What is the ArgoCD CLI and what are the most common commands used day-to-day? How does ArgoCD compare to Flux and when would you choose one over the other? What is server-side apply in ArgoCD and why might you enable it? How does ArgoCD handle notifications and what channels does it support? How do you perform a rollback in ArgoCD? What is the ArgoCD repository server caching strategy and how does it affect performance?
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