Input Parameter Confusion and Differences Between WorkflowTemplate and Workflows

[luke-hemisphere]

Summary

What happened?
Trying to submit a workflow template results in an error. The equivalent non-template workflow succeeds

argo -n argo template delete broken-template-inputs
> WorkflowTemplate 'broken-template-inputs' deleted

argo -n argo template create broken-template-inputs.yml
> Name:                broken-template-inputs
Namespace:           argo
Created:             Wed May 11 18:39:42 +1000 (now)

argo -n argo submit --from workflowtemplate/broken-template-inputs --watch 
> Failed to submit workflow: templates.main.tasks.A templates. inputs.parameters.px was not supplied`  

What version are you running?
3.3.2

Diagnostics

The following workflows are equivalent - one is a template and one is not.
running the template version will fail
running the non-template version will succeed

Template Version

apiVersion: argoproj.io/v1alpha1
kind: WorkflowTemplate
metadata:
  name: broken-template-inputs
  namespace: argo
spec:
  entrypoint: main
  arguments:
    parameters:
      - name: p1
        value: "1"
      - name: p2
        value: "2"
  templates:
    - name: main
      inputs:
        parameters:
          - name: p1
          - name: p2
      dag:
        tasks:
          - name: B
            arguments:
              parameters:
              - name: px
                value: "4"
            inline:
              inputs:
                parameters:
                  - name: px
              container:
                image: alpine:3.7
                command:
                  - sh
                  - -c
                  - exit 0
                
          - name: A
            arguments:
              parameters:
                - name: p1
                  value: "{{ inputs.parameters.p1 }}"
                - name: p2
                  value: "{{ inputs.parameters.p2 }}"
            inline:
              inputs:
                parameters:
                  - name: p1
                  - name: p2
              container:
                image: alpine:3.7
                command:
                  - sh
                  - -c
                  - exit 0

Workflow Version

apiVersion: argoproj.io/v1alpha1
kind: Workflow
metadata:
  generateName: broken-template-inputs-
  namespace: argo
spec:
  entrypoint: main
  arguments:
    parameters:
      - name: p1
        value: "1"
      - name: p2
        value: "2"
  templates:
    - name: main
      inputs:
        parameters:
          - name: p1
          - name: p2
      dag:
        tasks:
          - name: B
            arguments:
              parameters:
              - name: px
                value: "4"
            inline:
              inputs:
                parameters:
                  - name: px
              container:
                image: alpine:3.7
                command:
                  - sh
                  - -c
                  - exit 0
                
          - name: A
            arguments:
              parameters:
                - name: p1
                  value: "{{ inputs.parameters.p1 }}"
                - name: p2
                  value: "{{ inputs.parameters.p2 }}"
            inline:
              inputs:
                parameters:
                  - name: p1
                  - name: p2
              container:
                image: alpine:3.7
                command:
                  - sh
                  - -c
                  - exit 0

---

Message from the maintainers:

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[terrytangyuan]

Please check out some relevant documentation on WorkflowTemplate and parameters here: https://github.com/argoproj/argo-workflows/blob/master/docs/workflow-templates.md#working-with-parameters

[ezk84]

What's curious is, if I submit that illustrative example without supplying the values at the WorkflowTemplate's template level, it submits fine:

apiVersion: argoproj.io/v1alpha1
kind: WorkflowTemplate
metadata:
  name: hello-world-template-local-arg
spec:
  templates:
    - name: hello-world
      inputs:
        parameters:
          - name: msg
      container:
        image: docker/whalesay
        command: [cowsay]
        args: ["{{inputs.parameters.msg}}"]

apiVersion: argoproj.io/v1alpha1
kind: Workflow
metadata:
  generateName: hello-world-local-arg-
spec:
  entrypoint: whalesay
  templates:
    - name: whalesay
      steps:
        - - name: hello-world
            templateRef:
              name: hello-world-template-local-arg
              template: hello-world
            arguments:
              parameters:
                - name: msg
                  value: hola mundo

$ argo template create wft.yaml
Name:                hello-world-template-local-arg
Namespace:           argo
Created:             Thu May 12 11:11:33 +1000 (now)
$ argo submit wf.yaml 
Name:                hello-world-local-arg-25jmt
Namespace:           argo
ServiceAccount:      unset (will run with the default ServiceAccount)
Status:              Pending
Created:             Thu May 12 11:11:51 +1000 (now)
Progress:

Seems counterintuitive and counter to the idea of reusability if the argument values must be given at the WorkflowTemplate level instead of when that WorkflowTemplate's template is actually being used/called from a Workflow (as a utility function as it were). Am I misunderstanding the usage of WorkflowTemplates?

[asthinasthi]

The way I have mapped in my mind is:

WorkflowTemplate is the "library" function
Workflow is the wrapper around the library call or Library call in action.

In the WorkflowTemplate you are defining a function that accepts one input called msg (so no need to specify the value)
In the Workflow you are calling the ☝🏽 function so you have to pass the value to the input msg i.e. argument msg with value hola mundo

I have my own rants 😆 about Workflows but trying to see what you find counter intuitive

[ezk84]

Actually, what you have described is exactly how I picture it in my mind 😄 and what is counter intuitive is this line in the documentation linked above which negates this analogy we've created for ourselves:

When working with local parameters, the values of local parameters must be supplied at the template definition inside the WorkflowTemplate.

This is like having a requirement to give your function parameter values at the definition site instead of at the calling site.

What I was pointing out above is that if I take the yaml that is supposed to illustrate this requirement from the doco, remove the bit that gives the parameters values at the WorkflowTemplate level, and submit it to argo, it works just dandy. This is a further point of counterintuition 😜

[DiegoFlop]

The workflowTemplate is, as its name suggests, a template for the execution of one or more steps. In a workflow you refer to this template for several things:

1 The workflow file is smaller, which allows for better maintenance of the library.
2 Calls to workflowTemplate dynamically depending on previous steps or parameters received by argo-events for example.
3 Security, since you can prevent workflows that do not use templates from running, thus avoiding errors and standardizing workflows.

As a template you must provide the necessary parameters for its correct execution.

In a workflowTemplate you can use input parameters and workflow parameters, as needed.

[ezk84]

Just to make this a little more focused on the problem being shown here, I took the yaml posted by the OP and submitted it to my cluster:

$ argo submit wf.yaml --watch
Name:                broken-template-inputs
Namespace:           argo
ServiceAccount:      unset (will run with the default ServiceAccount)
Status:              Succeeded
Conditions:
 PodRunning          False
 Completed           True
Created:             Fri Jun 10 12:10:35 +0200 (12 seconds ago)
Started:             Fri Jun 10 12:10:35 +0200 (12 seconds ago)
Finished:            Fri Jun 10 12:10:45 +0200 (2 seconds ago)
Duration:            10 seconds
Progress:            2/2
ResourcesDuration:   8s*(100Mi memory),8s*(1 cpu)
Parameters:
  p1:                1
  p2:                2

STEP                       TEMPLATE  PODNAME                            DURATION  MESSAGE
 ✔ broken-template-inputs  main
 ├─✔ A                               broken-template-inputs-2304592408  9s
 └─✔ B                               broken-template-inputs-2354925265  9s
$ argo template create wft.yaml
Name:                broken-template-inputs
Namespace:           argo
Created:             Fri Jun 10 12:12:10 +0200 (1 second ago)
$ argo submit --from workflowtemplate/broken-template-inputs
time="2022-06-10T12:13:00.269Z" level=fatal msg="Failed to submit workflow: templates.main.tasks.A templates. inputs.parameters.px was not supplied"

So there we have it

• Error message suggests something is wrong with task A's px parameter, even though task A doesn't have this parameter.
• Task B has a px parameter AND it is being given a value, but error message says otherwise.

Thus I fail to see how this is not at least two bugs.

$ argo version
argo: v3.3.6
  BuildDate: 2022-05-26T01:07:24Z
  GitCommit: 2b428be8001a9d5d232dbd52d7e902812107eb28
  GitTreeState: clean
  GitTag: v3.3.6
  GoVersion: go1.17.10
  Compiler: gc
  Platform: windows/amd64