👋 in a flow that contains subflows in prefect 2.0, is there a way to specify

wait_for

between the subflows? i'll drop a trivial example in the thread

Yes, there is! In fact, if you use the SequentialTaskRunner, subflow_2 won't start until subflow_1 finishes.

from prefect.task_runners import SequentialTaskRunner


@flow(task_runner=SequentialTaskRunner())

ah ok! to add onto that, let's say i now also have another task that can run in parallel...is that possible? so the above example would go to

@task
def my_task():
    ...

@task
def my_task_2():
    ...

@flow
def subflow_1():
    my_task()
    my_task_2()

@flow
def subflow_2():
    my_task()
    my_task_2()

@flow
def my_flow():
    subflow_1()
    subflow_2()

and the hope would be that

my_task()

runs once and retrieves from cache once, but then

my_task_2()

can return to being run in parallel

the task runner can be attached to a flow (it determines how to run tasks in a flow; that's why it can't be set on a task), and you can have a different task runner attached to each subflow to ensure each flow/subflow has the parallelism you need

sorry for the delay, sounds good! sounds like that just means we'll need to structure our code in such a way to take advantage of some things being in parallel and other things not being in parallel

Exactly! and if you have any questions about it, let us know, we can certainly help and troubleshoot together