GitOps the Hard Way, with Argo CD

Argo CD in One Sentence, Then the Five-Step Loop

If we were to define Argo CD in one sentence, it would be: Argo CD is a declarative, GitOps continuous delivery tool for Kubernetes.

The "Declarative" part in the definition means that you define the desired state of your application in a Git repository, and Argo CD ensures that the live state of the application matches the desired state.

The "GitOps" part means that Git is the source of truth for the desired state of the application.

The deployment process is continuous because Argo CD continuously monitors the Git repository for changes and automatically applies those changes to the cluster.

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Argo CD makes deploying applications on Kubernetes repeatable, predictable, and auditable. A typical workflow with Argo CD looks like the following 5 steps:

1 - Define the desired state in Git: You define the desired state of the application, including all its Kubernetes objects, in a Git repository. Git holds the desired state, and every change to it is a commit you can review and trace. This is what we call the "single source of truth" in GitOps.

2 - Argo CD detects the difference: Argo CD polls the Git repository (or reacts to a webhook) and compares what is committed against what is running in the cluster. When the two diverge - because of a new commit, or because something changed the cluster directly - the Application is marked OutOfSync.

3 - Sync the application to the cluster: Argo CD applies the manifests to bring the cluster to the desired state. This is reconciliation, and it's what closes the gap between Git and the cluster.

4 - Monitor application health and sync status: Argo CD reports two separate things for every Application: sync status (does the cluster match Git?) and health status (are the resources actually running correctly?).

5 - Roll back when a deployment goes bad: If a synced change breaks something, you roll back.

To make this workflow possible, Argo CD runs as a set of components inside your cluster (after installation you can see them with kubectl get pods -n argocd). The core components are:

TODO: check names of pods

Component	What it does