# Argo CD

> [Argo CD] is a declarative GitOps continuous delivery tool, which allows
> developers to define and control deployment of Kubernetes application
> resources from within their existing Git workflow.

```sh
kubectl apply -k argocd
kubectl apply -f argocd/applications
```

## Components

Argo CD consists of several components, some of which are not used:

- [x] Application Controller
- [x] Repository Service
- [x] Web Server
- [x] Notification Controller
- [ ] ApplicationSet Controller[^1]
- [ ] Dex Server[^2]

[^1]: ApplicationSets are "generators" that can be used to apply applications
    to multiple clusters.  As we only have a single cluster, it is not useful.
[^2]: Argo CD includes Dex to handle authentication and authorization, but we
    are using Authelia instead.
    

## Applications

*Applications* are the core resource in Argo CD.  They form a collection of
resources associated with a particular application deployment.  They are
themselves defined as Kubernetes resources (see [applications]).


## Git Webhook

*Argo CD* will automatically refresh the desired state of applications whenever
a changeset is pushed to the Git repository where manifests are stored.  The
[infra/kubernetes] repository has a Webhook configured in Gitea that notifies
the Argo CD server on Git push events.


[Argo CD]: https://argo-cd.readthedocs.io/
[applications]: ./applications/
[infra/kubernetes]: https://git.pyrocufflink.blue/infra/kubernetes