Hello prefect logo, I have a flow with

task_a -> task_b

.

task_a

always succeed while

task_b

sometimes fails. When I go to retry the failing flow, I must rerun

task_a

before running

task_b

. What is the correct way of doing it in Prefect 2? I read about

refresh_cache

and

persist_result

but I am not sure

Hi Mattia, thanks for your question! Just to clarify, you want to rerun

task_a

every time you retry the flow, regardless of the inputs to the task staying the same?

Hello Bianca, yes exactly. In this case,

task_a

is installing dependencies that are needed by

task_b

. But since I ran this in AWS ECS, those dependencies need to be reinstalled every time the flow is retried

Hey Mattia - if you set

persist_result=False

on

task_a

, it should always rerun (which means it won't ever cache itself); I know this isn't the answer you're looking for, but we explicitly designed for this pattern in Prefect 3.0 with transactions:

with transaction():
    task_a()
    task_b()

^^^ will ensure that both tasks always rerun together, or, if they both complete successfully, stay cached together

Thank you Chris! This works for my current simple use case but I will definitely move to t_ransaction_ once I have migrated to Prefect 3 👀 😉