Thalamus

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OCM: Packaging Thalamus as a Component ​

Author: Henry Richter · Co-author: Artem Lytvynov

Thalamus is currently installed through a collection of Helm charts and configuration files wired together by a local helmfile. We need a packaging format that carries the whole installation description, including image references, and can be transported through an OCI registry we operate.

Technical deep dive ​

Together with the OCM team, and with direct help from Gergely Brautigam, we explored packaging the whole Thalamus installation as a set of OCM components. The prototype uses the idiomatic OCM deployment path: a single root component references sub-components for Thalamus itself, CRDs, operators, monitoring, and dependencies, and a ResourceGraphDefinition (RGD) orchestrates Flux OCIRepository and HelmRelease objects to deploy them.

We packaged Thalamus and its dependencies into OCM components with Helm charts and container images as resources, then used OCM's localization to rewrite image references to a registry we control. The RGD resolves each component resource to an OCI artifact and creates the corresponding Flux OCIRepository and HelmRelease objects. The root component-constructor.yaml declares the main component and its references:

yaml
components:
  - name: github.com/cobaltcore-dev/thalamus
    version: 0.1.0
    provider:
      name: cobaltcore-dev
    resources:
      - name: thalamus-chart
        type: helmChart
        version: 0.1.0
        input:
          type: Helm/v1
          path: helm/thalamus
          repository: charts/thalamus:0.1.0
      - name: thalamus-rgd
        type: blob
        version: 0.1.0
        input:
          type: File/v1
          path: ocm-single-component/deploy/rgd.yaml
          mediaType: application/vnd.cncf.kro.resourcegraphdefinition.v1+yaml
      - name: operator-image
        type: ociImage
        version: 0.1.0
        access:
          type: ociArtifact
          imageReference: ghcr.io/cobaltcore-dev/thalamus:latest
    componentReferences:
      - name: thalamus-crds
        componentName: github.com/cobaltcore-dev/thalamus/thalamus-crds
        version: 0.1.0
      # ... gateway-api-crds, gpu-operator, kube-prometheus-stack, open-webui, etc.

Future work ​

This packaging is still experimental, but it is a promising first step: it shows that Thalamus can be expressed as a transportable OCM component with localized image references, and that the approach maps well to our sovereignty and compliance requirements. Thanks to the OCM team and especially Gergely Brautigam for their help.