ArgoCD - Architecture and its Components

Introduction

ArgoCD is a declarative, GitOps-based continuous deployment tool for Kubernetes. It ensures that the desired state defined in a Git repository matches the actual state of a Kubernetes cluster. This approach enhances deployment consistency, security, and automation.

ArgoCD Architecture

• ArgoCD follows a client-server architecture and consists of the following key components:

1. API Server
   • The API Server acts as the core of ArgoCD, providing a RESTful API and a web-based UI.
   • It manages communication between the ArgoCD components and the users.
   • It is responsible for authentication, authorization, and serving the ArgoCD dashboard.
2. Repository Server
   • The Repository Server is responsible for interacting with Git repositories.
   • It fetches application manifests and processes them before passing them to the Kubernetes cluster.
   • This component ensures that the desired state of the cluster is always aligned with the version-controlled configuration.
3. Application Controller
   • The Application Controller is the brain of ArgoCD.
   • It continuously monitors the state of applications running in Kubernetes and compares them with the desired state in the Git repository.
   • If discrepancies are found, it attempts to bring the cluster back to the desired state automatically.
4. Dex (Optional Authentication Component)
   • ArgoCD integrates with Dex to support Single Sign-On (SSO) and authentication using external identity providers like GitHub, Google, LDAP, and SAML.
5. Redis (For Caching and Performance Optimization)
   • ArgoCD uses Redis as an in-memory database for caching application states, reducing the load on the system and improving performance.

ArgoCD Workflow

• Define Application Configuration in Git: Users store Kubernetes manifests, Helm charts, or Kustomize configurations in a Git repository.
• ArgoCD Monitors the Repository: The Application Controller continuously watches the Git repository for any changes.
• Syncing the Cluster State: When a change is detected, ArgoCD applies the new configuration to the Kubernetes cluster.
• Continuous Reconciliation: The Application Controller ensures the cluster state remains consistent with the Git repository, even if manual changes are made directly to the cluster.

Conclusion

ArgoCD simplifies and streamlines Kubernetes deployments by enforcing GitOps principles. Its architecture ensures that applications are deployed and maintained in a consistent, reliable, and secure manner. By integrating with Git, ArgoCD provides version-controlled and auditable deployments, making it an essential tool for modern cloud-native application delivery.