GitOps and Argo CD Lecture Notes

Introduction to GitOps

• Definition: GitOps is a practice to manage infrastructure and application configuration via Git.
• Configuration Management: Separates configuration settings from application source code, traditionally stored in version control.
• Public Clouds & Automation: Allow infrastructure configurations to be stored in Git repositories (e.g., Terraform).
• Main Concept: Git as the single source of truth for infrastructure management.

Infrastructure Management with GitOps

• Workflow: Changes made via pull requests, reviewed, merged, and applied automatically.
• Automation: CI/CD pipelines automatically detect and apply updates post-approval.
• Tools: Uses Terraform for declarative infrastructure setup.

Role of Argo CD

• Function: Ensures Git state syncs with Kubernetes state.
• Deployment Workflow:
  • Create a pull request for application deployment.
  • Argo CD applies changes upon PR approval.
  • Uses kubectl apply or helm upgrade to manage sync.

Continuous Integration and Continuous Delivery (CI/CD)

• Build Agent (e.g., Jenkins):
  • Pulls source code, runs tests, builds Docker image.
  • Releases images to Docker registry.
  • Updates image tag in GitOps repo.
• Argo CD:
  • Monitors GitOps repo for changes.
  • Applies updates automatically, enabling continuous delivery.

Setting Up Kubernetes with Minikube

• Purpose: Local Kubernetes cluster setup.
• Installation:
  • Use Docker driver for Minikube.
  • Configure kubectl to communicate with the cluster.

Installing Argo CD using Helm and Terraform

• Helm Charts: Common method to install open-source projects.
• Terraform Setup:
  • Define provider and resources for Helm charts.
  • Use helm_release resource for deployment.
• Configuration:
  • Override default variables in values.yaml.

Creating and Managing GitOps Repositories

• Public GitHub Repo:
  • Contains Kubernetes YAML files and Helm charts.
  • Used to operate the Kubernetes cluster through GitOps.
• Docker Hub:
  • Stores public Docker images.
  • Authentication needed for private images.

Automating CI/CD with Scripts

• Script Creation: For build agents to automate deployments.
• Functions:
  • Tag and push Docker images.
  • Modify GitOps repository with new image tags.

Advanced GitOps Patterns

• Application Management:
  • Use Argo CD Application CRDs for registration.
  • Enable automatic sync with Kubernetes.
• App of Apps Pattern: Manage multiple apps and environments.

Using Private Repositories and Docker Images

• Private Repos: Use SSH keys for authentication.
• Docker Hub Tokens: Secure image pull for Kubernetes.

Deploying Helm Charts with Argo CD

• Example: Metrics-server chart for resource metrics.
• Overrides: Use YAML files to customize deployments.

Kustomize for Deployment Customization

• Purpose: DRY principle, environment-specific overrides.
• Structure:
  • Base folder for shared resources.
  • Environment folders for specific customizations.

Conclusion

• Argo CD and GitOps: Streamline CI/CD pipelines and deployment management.
• Future Topics: Explore image updater for decoupling CI and CD.