helm-chart-resource

Helm Chart Resources in the Component Descriptor

For prerequisites see here.

The blueprint of the previous examples reference the Helm chart directly like this:

chart:
  ref: eu.gcr.io/gardener-project/landscaper/examples/charts/hello-world:1.0.0

However, it is recommended to collect all resources of a component in its component descriptor and reference these resources in the blueprint only by their name in the component descriptor. This has the advantages that you have exactly one location, listing all resources required to deploy a component and if you just want to update the version of a resource, you only need to update its entry in the component descriptor. No change of the blueprint is required.

Therefore, we will now modify the previous example as follows:

• We extend the resource list of the component descriptor by an entry for the Helm chart.
• We also modify the blueprint such that it takes the address of the Helm chart from the new entry of the component descriptor.

The Component Descriptor

You can find the extended component descriptor here, and in the OCI registry here.

Its list of resources has now two entries, one for the blueprint and one for the Helm chart. The entry for the Helm chart has the name hello-world-chart and contains the address in the OCI registry.

Referencing the Helm Chart

The deploy execution in the blueprint has been modified so that it takes the Helm chart address from the component descriptor:

chart:
  {{ $chartResource := getResource .cd "name" "hello-world-chart" }}
  ref: {{ $chartResource.access.imageReference }}

Note that the deploy execution is a Go template. Landscaper provides a function getResource which is used here to get the resource entry with name hello-world-chart from the component descriptor. The variable chartResource has then the resource entry as value, and the expression ref: {{ $chartResource.access.imageReference }} evaluates to the same value as before.

Procedure

The procedure to install the helm chart with Landscaper is the same as before:

1. Insert in file target.yaml the kubeconfig of your target cluster.

2. On the Landscaper resource cluster, create namespace example and apply the context.yaml, the target.yaml, and the installation.yaml:

   kubectl create ns example
   kubectl apply -f <path to context.yaml>
   kubectl apply -f <path to target.yaml>
   kubectl apply -f <path to installation.yaml>

Remark on Charts Stored in a Helm Chart Repository

Let us mention a variation of this example. Above, we have stored our Helm chart in an OCI registry as described in Use OCI-based registries. Of course, you can also store your Helm chart in a Helm chart repository. In that case, the entry in the component descriptor would have the following format:

  resources:
    - name: example-chart
      type: helm.io/chart
      version: 1.0.0
      relation: external
      access:
        type: helmChartRepository
        mediaType: application/octet-stream
        helmChartRepoUrl: <helm chart repo url>
        helmChartName:    <helm chart name>
        helmChartVersion: <helm chart version>

The chart section in the deploy execution of the blueprint, would then look like this:

  chart:
    helmChartRepo:
      {{- $chartResource := getResource .cd "name" "example-chart" }}
      helmChartRepoUrl: {{ $chartResource.access.helmChartRepoUrl }}
      helmChartName:    {{ $chartResource.access.helmChartName }}
      helmChartVersion: {{ $chartResource.access.helmChartVersion }}