ArgoCD — App of Apps, ApplicationSets, sync policies and hooks — CI/CD, GitOps, DevSecOps & Observability

ArgoCD is a declarative, GitOps-native continuous delivery tool for Kubernetes. It operates as a Kubernetes controller that continuously watches one or more Git repositories and automatically synchronises the cluster state to match the declared desired state. ArgoCD's UI, CLI, and API make the synchronisation status of every Application visible in real time, providing the observability layer that the GitOps model requires.

Four capabilities distinguish ArgoCD from a simple apply-on-push script: the App of Apps pattern for managing fleets of applications, ApplicationSets for generating Applications programmatically across environments and clusters, sync policies for controlling automation behaviour, and sync hooks for injecting ordered operations—such as database migrations or smoke tests—into the deployment lifecycle. Together these capabilities make ArgoCD suitable for organisations managing dozens of services across multiple clusters.

Analogy🏏Cricket

Think of it like cricket: Imagine the BCCI's team management system for an international tour with matches in three different countries simultaneously. Rather than a coordinator manually managing each match day's logistics, the system reads the official tour schedule document and automatically dispatches the right squad, equipment, and support staff to each venue. When the tour schedule changes—a match is rescheduled, a squad member is replaced—the system detects the change and updates the arrangements automatically. Just as the tour management system uses the official document as the source of truth and orchestrates multiple concurrent deployments to multiple venues, ArgoCD uses the Git repository as the source of truth and orchestrates multiple concurrent Application syncs to multiple clusters. Just as the system provides a dashboard showing which venues are 'ready', 'delayed', or 'degraded', ArgoCD provides a dashboard showing which Applications are Synced, OutOfSync, or Degraded. This reveals why ArgoCD is valued at scale: managing dozens of applications across multiple clusters manually is operationally equivalent to coordinating an international cricket tour by phone.