question about Complex depends condition in Hera

[sparkstar]

Hello Hera workflow team. I have a question about complex condition in hera workflow.

I am currently using argo workflow on my complex job processing and have decided to change from yaml to hera's. but I wonder about the proper way to create complex workflow in Hera like argo workflow yaml.

for example, my argo workflow yaml has these conditions:

- name: complex-conditions
  depends: (decoder.Skipped && extractor.Skipped) || (decoder.Succeeded || extractor.Succeeded)
  ...
  ...
- name: complex-condition-2
  depends: (decoder.Skipped && filecheck.Skipped && extractor.Omitted) || (decoder.Succeeded || redictor.Succeeded)
  ...
  ...

parentheses depends is here. I thought that the next function in hera would be a solution but it seems insufficient.

    with Workflow(...) as w:
        example_function = Task('example-function', RandConditional)
        example_function2 = Task('example-function2', RandConditional)
        example_function3 = Task('example-function3', RandConditional)
        example_function4 = Task('example-function4', RandConditional)
        example_function5 = Task('example-function5', RandConditional)

        example_function.next(example_function2)
        example_function.next(example_function3)
        example_function.next(example_function4)

        example_function2.next(example_function5, Operator.And, TaskResult.Failed)
        example_function3.next(example_function5, Operator.And, TaskResult.Succeeded)
        example_function4.next(example_function5, Operator.And, TaskResult.Succeeded)

this code to

      - name: example-function
        template: example-function
      - depends: example-function
        name: example-function2
        template: example-function2
      - depends: example-function
        name: example-function3
        template: example-function3
      - depends: example-function
        name: example-function4
        template: example-function4
      - depends: example-function2.Failed && example-function3.Succeeded && example-function4.Succeeded
        name: example-function5
        template: example-function5

but

        ...
        ...
        example_function.next(example_function3)
        example_function.next(example_function4)

        example_function2.next(example_function5, Operator.And, TaskResult.Failed)
        example_function3.next(example_function5, Operator.And, TaskResult.Succeeded)
        example_function4.next(example_function5, Operator.And, TaskResult.Succeeded)

        example_function2.next(example_function5, Operator.Or, TaskResult.Success)
        example_function3.next(example_function5, Operator.And, TaskResult.Success)
        ...

I expected complex depends but i got ValueError

#expected
      - depends: example-function2.Failed && example-function3.Succeeded && example-function4.Succeeded || example-function2.Succeedeed && example-function3.Succeedeed
        name: example-function5
        template: example-function5

# ValueError: example-function2 already in example-function5's depends: example-function2.Failed && example-function3.Succeeded && example-function4.Succeeded

I want to any suggestion on these problem. I read manual and hera's issue many times, but i cannot found.

How to I solve this situations?

[flaviuvadan]

Hi @sparkstar! Thank you for the question! Any chance you checked out the Hera expr module? It's supposed to help create these complex expressions. Once you have an expression, you can modify the Task.depends field manually. Hera cannot capture the enormous complexity of the depends field via pure functions so we went with an expr module that allows expressing this complexity, plus made the depends field a public attribute so the condition can be set! Does this help?

[sparkstar]

Thanks. I will try to use expr.

[flaviuvadan]

@sparkstar I am closing this for now. If you'd like to further discuss the use of expression feel free to reopen this issue! Thanks again for the question :)

[Elena-GHub]

Hi @flaviuvadan!
I am also moving some yaml files to hera and I am in a similar scenario as the original poster with dependencies that are more complex than what I have seen in the examples.
I have clicked on the Hera expr module link you mentioned earlier but I get a "Not Found" error. Do you have the current location where I can read about this module?
Thanks in advance!

[edit] I think I found it. I will check it out.

[flaviuvadan]

Thanks for the question @Elena-GHub! Yea, we have adjusted our documentation since the original answer was accepted. Thanks for pointing that out! I edited the original answer to reflect the new link: https://hera-workflows.readthedocs.io/en/latest/expr/

[Elena-GHub]

Thanks @flaviuvadan!