How to Implement a Looping Workflow in Hera Based on a Script's Output Condition?

[xiki-tempula]

Hi,

I have an Argo workflow script that takes in two arguments, A: list and B: list, and returns A: list, B: list, and C: bool. I want to repeatedly run this script while C is True and exit the loop when C is False, similar to the following Python code:

A, B, C = script(A, B)
while C:
    A, B, C = script(A, B)

How can I implement this workflow using Hera? Any guidance would be greatly appreciated.

Thanks!

[elliotgunton]

Hey @xiki-tempula, you can do this using a DAG that will "recurse" on itself:

from hera.workflows import DAG, Task, Workflow, script

@script()
def random_roll():
    import random

    print(random.randint(1, 6))

with Workflow(generate_name="recursive-dag-", entrypoint="dag") as w:
    with DAG(name="dag") as dag:
        random_number = random_roll(name="roll")
        recurse = Task(
            name="recurse-if-not-six",
            template=dag,
            when=f"{random_number.result} != 6",
        )
        random_number >> recurse

There is also a recursive steps example if that's easier

[elliotgunton]

Added as an example in #1351