echo-server

Echo Server Example

In this example, we use the Landscaper to deploy an echo server.

For prerequisites, see here.

The example uses the following resources:

• a blueprint, which you can find locally, and uploaded in an OCI registry,
• a Helm chart which you can also find locally and uploaded in an OCI registry,
• the Docker image hashicorp/http-echo as an external resource.

All these resources are listed in the component descriptor. It is an advantage to have them all in one place, in a standard format. Otherwise, you would have to search images spread somewhere in charts, perhaps even mixed with some templating. Moreover, the component descriptor can be used by other tools for example for transport or signing.

OCI Image Resource in the Component Descriptor

The echo-server Helm chart in this example consists of a Deployment and a Service. The Deployment uses a container image. However, instead of a hard-coded image reference in the deployment.yaml, we rather maintain the image reference in the component descriptor. In detail, the connection is the following:

• The component descriptor contains a resource with name echo-server-image and a reference to the actual image:

  name: echo-server-image
  type: ociImage
  version: v0.2.3
  relation: external
  access:
    type: ociRegistry
    imageReference: hashicorp/http-echo:0.2.3

• The blueprint contains a template for a DeployItem. Part of this is a section values for the Helm values. During the templating, we read the entry echo-server-image of the component descriptor, extract the field access.imageReference, and write it into the section with Helm values:

  values:
    {{ $imageResource := getResource .cd "name" "echo-server-image" }}
    image: {{ $imageResource.access.imageReference }}

  After the templating, the resulting DeployItem contains the image reference in its values section:

  values:
    image: hashicorp/http-echo:0.2.3

• Finally, the deployment.yaml of the chart takes the image from the Helm values:

  containers:
    - image: {{ .Values.image }}

Procedure

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

1. Add the kubeconfig of your target cluster to your target.yaml.

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>

3. To try out the echo server, first define a port forwarding on the target cluster:

   kubectl port-forward -n example service/echo-server 8080:80

   Then open localhost:8080 in a browser.

   The response should be "hello world", which is the text defined in the values.yaml of the chart.