Helm Charts

Helm is like a package manager for applications running on Kubernetes. With Yaook Operator and the supporting services being an application running on Kubernetes, it only makes sense to offer it as a Helm chart to deploy into a cluster.

Note

The official Yaook Helm Chart registry is at https://charts.yaook.cloud/operator/stable/.

Helm Chart generation

A working Yaook cluster depends on three pieces of generated-from-source information in order to function:

  • The CustomResourceDefinitions are built using cuelang to deduplicate shared bits in them

  • The Roles and ClusterRoles for operators are generated from the source code based on the privileges needed to run it.

  • The versions of the images used in all components.

That means that static Helm charts, where all manifest templates are contained within a templates directory, are not a solution.

Helm Chart builder

The Helm Chart builder is located in yaook/helm_builder. The chart templates are located in yaook/helm_builder/Charts. That directory also contains a README file with an overview of the structure of a Chart template.

Using the Helm Chart builder

Note

This documentation should be moved into a user guide; it is not an implementation detail.

You can run the Helm Chart builder using:

python -m yaook.helm_builder -vvv -a

This will build all charts. To also upload charts to the repository, add -U to the command line flags and set the GITLAB_USERNAME, CI_JOB_TOKEN and CI_PROJECT_ID environment variables.

To only build a subset of charts, remove the -a and name the charts explicitly (with either their directory name or an absolute path to the chart template directory).

Creating a new Helm Chart

  • Create a folder in /yaook/helm_builder/Charts. This will be your Chart template folder (not to be confused with the standard templates folder within that Chart template folder). The name of the folder will become the name of your helm chart.

  • Create a subfolder templates. Place your Helm manifest templates and partials in that folder.

  • Create chart-template.yaml.j2. This is a Jinja2 Template which will be rendered by the Helm builder to create the Chart.yaml for the Chart. See the README in the Charts directory for details.

  • Create values-template.yaml.j2. This is a Jinja2 Template which will be rendered by the Helm builder to create the values.yaml for the Chart. See the README in the Charts directory for details.

  • Test building your chart using:

    $ python3 -m yaook.helm_builder -vvv your-chart-name

    Check the contents of the generated Chart.yaml and values.yaml. You may also test deploying your Chart using helm install ... releasename ./yaook/helm_builder/Charts/your-chart-name, optionally with --dry-run.

You can check out the existing charts for an example.