Hi I m trying to write a flow that has a nested for while lo

Question

Hi I m trying to write a flow that has a nested for while loop where the while loop contains multiple tasks I don t think this is possible it s sort of a combination of and task Any pointers ideas for how to solve this pattern Or is it definitely not possible Here s what kinda what the code looks like

Kevin Kho · Answer

Hey < Casey Green> been thinking about this for a bit and I don t think there is a way to get this to work because LOOPING itself is confined to one task Looping over multiple tasks breaks the acyclic nature of the DAG So I think you need to combine this into one big `run job` task and then LOOP there You can just do `trigger job run ` and `wait to complete run ` inside the big task but they will just be like functions instead of Prefect tasks

Casey Green · Answer

gotcha that makes sense since this wouldn t be a valid DAG thanks pray

Casey Green · Answer

If I were to make this a flow instead is it possible to automatically trigger retries at the flow level e g ```with Flow test as flow flow name = Parameter flow name required=True handle = trigger job job name result = wait to complete handle max runs = 3 maybe this isn t a case perhaps a terminal state handler that inspects the result and sets the state appropriately with case should re run result True trigger flow failure but automatically retry ``` Kinda looks and feels like a code smell man shrugging

Casey Green · Answer

I guess really what I m trying to do is to retry an entire sub branch of a DAG

Casey Green · Answer

which maybe is a weird invalid thing to want to do man shrugging

Kevin Kho · Answer

We don t have retries at the Flow run level but if it is invoked through a `StartFlowRun` task or `create flow run` task then we have retries but the concept of a flow retry is not definitive because some users expect everything to run even successful tasks and some expect to run from where it left off I think retries on these two Prefect tasks can be used for both scenarios by supplying a `idempotency key`

Casey Green · Answer

oh interesting I ll take a look at this task this might work