templating metrics with Helm

[sabreensalama]

Hi, I have many argo-workflow templates and I need to define a custom metrics to monitor the duration of each workflow, but everytime I got this error

at <duration>: wrong number of args for duration: want 1 got 0
Use --debug flag to render out invalid YAML

although I make sure that the template is correct, here is the template-file, is there any help?

apiVersion: argoproj.io/v1alpha1
kind: WorkflowTemplate
metadata:
  name: wft-cassandra-e2e
spec:
  entrypoint: cassandra-e2e

  templates:
  - name: cassandra-e2e
    metrics:
     prometheus:
      - name: exec_duration_gauge
        labels:
          - key: name
            value: wft-cassandra-e2e
        help: "Duration gauge by name"
        gauge:
          realtime: true
          value: {{ duration }}
    dag:
      tasks:
      - name:  load
        templateRef:
          name: load
          template:load
      - name: load-2
        depends: load
        templateRef:
          name: load-2
          template: load-2

[agilgur5]

I think you meant to use "{{ workflow.duration }}".
Your Workflow has plain {{ duration }}, which seems to be being interpreted as a function.

See also the example in the docs:

# ...
        gauge:
          value: "{{ workflow.duration }}"

EDIT: {{ duration }} is also valid. Per the answer, OP was using Helm and didn't escape the expression syntax -- the error was from Helm, not Argo.

[sabreensalama]

I tried it with {{ workflow.duration }} but i got an error : function "workflow" not defined

[agilgur5]

It sounds like you're trying to put the resource through Helm?
You did not mention that in your question, but that is a very important detail 😕 That would explain why it interpreted duration as a function, despite not using an Argo expression. And workflow is indeed not a Helm function, it is an Argo variable.
I thought the error sounded off initially, but did not think Helm were being used without mention...

If you're using Helm templating, you need to escape Argo's own templating. helm/helm#2798 lists several ways of doing so. The one I am most familiar with is "Option 1" from this SO answer (written by an Argo CD maintainer).
Here's how you could use that for your template:

# ...
        gauge:
          value: "{{`{{ workflow.duration }}`}}"

The links above describe how this works in detail, but basically the backticks tell Helm to render the inner string as-is as a literal. That makes Helm render the Argo syntax out properly.

[sabreensalama]

it is my bad sorry for that, I just started with helm , argocd and argo-workflow, really thank you, it is work fine now