Argo CD

Argo CD is a declarative GitOps continuous delivery tool for Kubernetes. It watches a Git repository for desired application state and automatically synchronizes the live cluster to match, providing drift detection and a visual interface for deployment status.

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Don't Panic — Argo CD

Argo CD is a Kubernetes delivery controller with one persistent question: does the cluster still look like the version of the application described in Git? That is less theatrical than launching a deployment pipeline, but it is much more difficult to ignore at three in the morning. Git supplies the desired version. Kubernetes supplies the unruly evidence. Argo CD compares them until somebody decides what happens next.

The thing it replaces is the familiar arrangement where a build system carries cluster credentials, applies manifests once, and declares the matter closed. Here the build still tests code and makes artifacts. A change to configuration records which artifact and settings belong in an environment. The Application, which joins a source, destination, project, and sync policy, gives Argo CD a bounded piece of that declaration to watch.

The useful distinction is between target state and live state. Target state is what Argo CD renders from the selected repository revision, path, chart, or other supported source. Live state is what it finds in the destination cluster. A sync moves live resources toward target resources; a refresh only recalculates the comparison. The vocabulary is calm. The consequences of confusing the two are notably less calm.

There is also health, which is not another spelling of Synced. An Application can match Git exactly while its Pods fail to become ready. It can be OutOfSync while an existing workload still serves traffic. The course slides map the controller, repository server, and API server if you want the machinery; the cheatsheet keeps the commands, status meanings, hooks, waves, and AppProject controls close at hand.

Automation deserves the same suspicion normally reserved for a robot holding a large pair of scissors. Automated sync applies qualifying target changes. Prune permits deletion when resources vanish from target state. Self-heal corrects live-only drift. Allow-empty permits a target with no resources to remove everything it manages. Each control is separate because its failure mode is separate.

Argo CD also does not perform every task that happens to be near deployment. It does not build images, prove a change safe, replace a secret store, or turn an unsafe database migration into a safe one by arranging it in a charming sequence of sync waves. Read the intro for the full operating boundary, then use the practice reference and exercise to make one Application report, diff, sync, and become healthy in an isolated cluster.

Don't Panic — Argo CD

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