Argo Workflows: Set container image from enviroment variables

Question

I'm trying to set the container image for a template from environment variables. I've tried this:

- name: sftp-to-gcp-bucket
    script:
      image: "gcr.io/{{$CONTAINER}}/imagename:{{$VERSION}}"
      ...
      ...
      env:
      - name: CONTAINER
        valueFrom:
        secretKeyRef:
          name: enviroment-vars
          key: contenedor
      - name: VERSION
        valueFrom:
        secretKeyRef:
          name: enviroment-vars
          key: version

And I have the k8s secrets set correctly:

Name:         enviroment-vars
Namespace:    argo
Labels:       <none>
Annotations:  <none>

Type:  Opaque

Data
====
container:                  17 bytes
version:                    5 bytes

But the env variables doesn't seem to get injected into the image field... Do I have to make another template to parse the secrets and from that output inject them into the image?

Answer 1

The environment variables only have meaning in the container created by Argo Workflows. They are not accessible in the Workflow itself.

There are a number of ways to load Kubernetes resources and use them as variables in a Workflow.

In this case, I'd recommend loading parameters from a ConfigMap.

apiVersion: argoproj.io/v1alpha1
kind: Workflow
spec:
  templates:
  - name: sftp-to-gcp-bucket
    inputs:
      parameters:
        - name: container
          valueFrom:
            configMapKeyRef:
              name: enviroment-vars
              key: contenedor
        - name: version
          valueFrom:
            configMapKeyRef:
              name: enviroment-vars
              key: version
    script:
      image: "gcr.io/{{inputs.parameters.container}}/imagename:{{inputs.parameters.version}}"