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03 – GitOps & ArgoCD

Focuses on GitOps concepts, ArgoCD usage, the app-of-apps pattern, and ApplicationSets.

Table of Contents

  1. What is GitOps?
  2. ArgoCD as a GitOps Tool
  3. App-of-Apps Pattern
  4. Adding a New App Under a Root “Umbrella”
  5. ApplicationSet (Uses & Generators)
  6. Scenario: Deprecated APIs Causing ArgoCD Sync Failures
  7. Scenario: Namespace Conflicts in ArgoCD Applications

1) What is GitOps?

Question:
Your manager says, “We should do GitOps!” How do you explain the core idea of GitOps?

Hints / Key Points
  • Infrastructure and app config in Git as the single source of truth.
  • A tool (ArgoCD) automatically updates the cluster to match Git.
  • All changes go through PRs, so everything is tracked and auditable.

2) ArgoCD as a GitOps Tool

Question:
Why is ArgoCD considered a GitOps solution and not just another deployment tool?

Hints / Key Points
  • Watches a Git repo for changes, automatically syncing them into the cluster.
  • Declarative approach: no manual clicks or imperative commands.
  • Integrates with Helm, Kustomize, or plain YAML.

3) App-of-Apps Pattern

Question (Scenario):
You have a bunch of microservices, each with its own repo or chart. You want a single place to manage them. How would you do this in ArgoCD?

Hints / Key Points
  • Root “umbrella” application referencing multiple child apps.
  • Each child is a separate Helm chart or folder.
  • App-of-apps keeps everything organized under one main config.

4) Adding a New App Under a Root “Umbrella”

Question:
If you already have a root “app-of-apps” that manages several services, how do you add a brand-new microservice?

Hints / Key Points
  • Create a new ArgoCD “child” Application in the same or separate repo.
  • Reference it in the root app’s YAML so ArgoCD picks it up.

5) ApplicationSet (Uses & Generators)

Question:
What is an ApplicationSet in ArgoCD, and when might you use it? Name at least one generator type.

Hints / Key Points
  • ApplicationSet is a CRD that can create multiple ArgoCD Applications automatically.
  • Used for deploying the same app across multiple clusters or generating apps for each folder/branch.
  • Generators: List, Git directory, Cluster, or SCM provider.

6) Scenario: Deprecated APIs Causing ArgoCD Sync Failures

Question:
After upgrading Kubernetes, an ArgoCD application fails to sync due to deprecated APIs in its Helm chart (e.g., extensions/v1beta1 → apps/v1).

  • How do you identify which APIs are outdated?
  • How do you fix them?
Hints / Key Points
  • Check chart templates for old API references.
  • Replace them with newer versions (apps/v1).
  • Tools like Pluto or helm template can highlight deprecated APIs.
  • Keep charts updated and test in a staging cluster before upgrading production.

7) Scenario: Namespace Conflicts in ArgoCD Applications

Question:
Two ArgoCD applications deploy into the same namespace, causing resource conflicts (e.g., overlapping ConfigMaps). One of them fails to sync.

  • How would you troubleshoot and resolve it?
  • How do you prevent it in the future?
Hints / Key Points
  • Identify which resources clash by checking logs or ArgoCD sync errors.
  • Move each app into its own namespace for isolation, or rename the conflicting resources.
  • Have a clear naming/namespace strategy so multiple apps don’t step on each other.