ADR0007 - Helm Tooling

ArgoCD is a Continuous Delivery tool for Kubernetes that can manage Helm charts. It renders Helm charts and applies them to the cluster. It has a lot of features and is very flexible. It comes with a well designed, multi-tenancy capable Web UI and a CLI tool.

ArgoCD needs to be backed by a Git repository. This does not fit well with user-self-serviced services that are managed by the change tracking system.

It renders charts on apply and translates Helm hooks into ArgoCD hooks. There can be some friction between Helm and ArgoCD hooks, they do not work exactly the same way and some Helm hooks are not supported by ArgoCD.

ArgoCD is rather heavy weight with many managed components and a lot of moving parts.

The author is not sure if we can pre-render Helm charts for diff tracking in earlier stages of the change tracking system.

The K3s Helm controller is a lightweight controller that renders and applies Helm charts. Rancher uses the controller to bootstrap their K3s clusters.

It executes Kubernetes jobs to render Helm charts and applies them to the cluster.

Due to the controller just calling Helm commands inside a container it supports all Helm features and is rather flexible.

As of the time of writing this ADR the controller does not yet support Helm 4.x.

The error reporting does not seem as robust as ArgoCD or FluxCD. The CRD basically reports, queued, ok, or failed and the logs of the Helm job need to be inspected for more details.

The FluxCD GitOps framework is a Continuous Delivery framework for Kubernetes that can manage Helm charts.

It was a fully featured Helm controller with awesome documentation. The controller is very up to date and supports Helm 4.x. It supports all Helm features known to the author. It is very well designed, has options for sharding on big clusters, and is very flexible.

FluxCD additionally provides controllers for easier handling of OCI repositories and legacy chart repositories. Those controllers handle authentication, signature verification, caching, and versioning of Helm charts and OCI images.

The controllers have a lightweight footprint on the cluster and are very modular.

FluxCD makes no assumptions of underlying Git repositories and can be used with any Git repository.

Using the FluxCD GitOps framework allows us to implement a lightweight change tracking system without having to worry about registry and Helm specific details.

Crossplane has a Helm function that can render and apply Helm charts. The author did not further investigate what features are supported because they were put off by the complexity and bad documentation.

Building our own Helm controller would allow us the most flexibility and control over the features we want to support. We would need to implement a lot of features that are already implemented by the other controllers. The maintenance burden would be high and we would need to keep up with Helm releases and changes.