Subflow Task Runner Inheritance

[daviddwlee84]

I would like to know the behavior of the task runner.
If I specify a task runner on the parent flow, will the subflow also use the same task runner?
Or will it get overridden if I set a different task runner to the subflow's flow decoration?

For example:

from prefect import flow
from prefect.task_runners import ConcurrentTaskRunner
from prefect_ray.task_runners import RayTaskRunner

@flow(task_runner=ConcurrentTaskRunner())
def child_flow():
    # do something
    pass

@flow(task_runner=RayTaskRunner())
def parent_flow():
    child_flow()

if __name__ == "__main__":
    parent_flow()

Will it use RayTaskRunner or ConcurrentTaskRunner on the child_flow?

If so, I think overriding subflow's task runner can be easily done by invoking the with_options.
If not, do I have a way to pass down the task runner from the top flow?

https://chat.openai.com/share/a3e95e9e-97ae-463f-a13f-c6f4cbaa02d1

[daviddwlee84]

Seems subflows are not concurrent now

• Ability to run subflows concurrently with synchronous tasks in subflows · Issue #7322 · PrefectHQ/prefect
• Add Flow.submit interface for subflows · Issue #6689 · PrefectHQ/prefect

[daviddwlee84]

Inherit task runner from parent flow can be done like this

from prefect import flow
from prefect_ray.task_runners import RayTaskRunner
from prefect.context import FlowRunContext

@flow
def child_flow():
    # do something
    pass

@flow(task_runner=RayTaskRunner(), log_prints=True)
def parent_flow():
    print(f"Inherit parent flow task runner {FlowRunContext.get().task_runner}")
    child_flow.with_options(task_runner=FlowRunContext.get().task_runner)()

if __name__ == "__main__":
    parent_flow()