Cannot use parameter substitution for volume size

[NicolasRouquette]

Expected Behavior

Apply the following resource:

apiVersion: tekton.dev/v1alpha1
kind: Task
metadata:
  name: buildah
spec:
  inputs:
    params:
      - name: BUILDER_IMAGE
        type: string
        description: The location of the buildah builder image.
        default: quay.io/buildah/stable
      - name: DOCKERFILE
        type: string
        description: Name of the dockerfile relative to the context directory.
        default: Dockerfile
      - name: CONTEXT
        type: string
        description: Path to the dockerfile directory relative to the root of the repository.
        default: .
      - name: FORMAT
        type: string
        description: one of oci, v2s1, v2s2.
        default: v2s1
      - name: TLSVERIFY
        type: string
        description: Verify the TLS on the registry endpoint (for push/pull to a non-TLS registry)
        default: "true"
      - name: MEMORY
        type: string
        description: Size of /var/lib/containers in G units.
        default: 5G
    resources:
      - name: source
        type: git

  outputs:
    resources:
      - name: image
        type: image

  steps:
    - name: build
      image: $(inputs.params.BUILDER_IMAGE)
      workingDir: /workspace/source/$(inputs.params.CONTEXT)
      # See: https://github.com/containers/buildah/issues/1481#issuecomment-480629425
      command: ['buildah', 'bud', '--isolation', 'chroot', '--tls-verify=$(inputs.params.TLSVERIFY)', '-f', '$(inputs.params.DOCKERFILE)', '-t', '$(outputs.resources.image.url)', '.']
      volumeMounts:
        - name: varlibcontainers
          mountPath: /var/lib/containers

    - name: images
      image: $(inputs.params.BUILDER_IMAGE)
      workingDir: /workspace/source
      command: ['buildah', 'images', '--all', '--format', '{{.Digest}} {{.Size}} {{.CreatedAt}} {{.Name}}']
      volumeMounts:
        - name: varlibcontainers
          mountPath: /var/lib/containers

    - name: push
      image: $(inputs.params.BUILDER_IMAGE)
      workingDir: /workspace/source
      command: ['buildah', 'push', '--debug', '--format', '$(inputs.params.FORMAT)', '--tls-verify=$(inputs.params.TLSVERIFY)', '$(outputs.resources.image.url)', 'docker://$(outputs.resources.image.url)']
      volumeMounts:
        - name: varlibcontainers
          mountPath: /var/lib/containers

  volumes:
    - name: varlibcontainers
      emptyDir:
        sizeLimit: $(inputs.params.MEMORY)
        medium: Memory

We should get:

tkn tasks ls
NAME       AGE
buildah     ...

Actual Behavior

tkn tasks ls
Failed to list tasks from ... namespace 
Error: v1alpha1.TaskList.ListMeta: v1.ListMeta.TypeMeta: Kind: Items: []v1alpha1.Task: v1alpha1.Task.Spec: v1alpha1.TaskSpec.Volumes: []v1.Volume: v1.Volume.Name: VolumeSource: EmptyDir: v1.EmptyDirVolumeSource.SizeLimit: unmarshalerDecoder: quantities must match the regular expression '^([+-]?[0-9.]+)([eEinumkKMGTP]*[-+]?[0-9]*)$', error found in #10 byte of ...|s.MEMORY)"},"name":"|..., bigger context ...|um":"Memory","sizeLimit":"$(inputs.params.MEMORY)"},"name":"varlibcontainers"}]}}],"kind":"TaskList"|...

Steps to Reproduce the Problem

1. kubectl apply -f <file> where ` is the task described above
2. tkn tasks ls

Additional Info

This behavior suggests that it is currently not possible to define tekton parameters for cpu or memory characteristics (quota or limits). Are there other similar limitations?

[vdemeester]

/kind feature

[dibyom]

Is this more of a bug than a feature?

[NicolasRouquette]

It depends on how you interpret the doc, specifically: https://github.com/tektoncd/pipeline/blob/master/docs/tasks.md#variable-substitution

and:

https://github.com/tektoncd/pipeline/blob/master/docs/tasks.md#variable-substitution-within-volumes

Nothing in the doc currently says that one can use variable substitution for volume characteristics.
So, in a strict sense, this will be a new feature.

[afrittoli]

Thanks for reporting this!
Hopefully the need of this feature is reduced by the work on workspaces.
In any case I will leave this one in the backlog.

[dibyom]

Related to #1530

[bobcatfish]

I think we're tending toward moving away from specifying volumes in Tasks now that we have workspaces (and #2326 adds the ability to create volumes w/in a Run) - we even considered removing volumes altogether #2058. So I'm going to close this for now but please re-open if you feel like workspaces can't meet your needs (and/or open another issue with required features for workspaces!)

Thanks @NicolasRouquette 🙏