@Marvin i have subflows_01, ... 10 created from a main flow; if one subflow fails is it possible to re-run that flow and have the main flow continue?

In Prefect, subflows are considered child flows to the main flow (referred to as the parent flow). Subflow runs behave like normal flow runs and have a full representation in the backend as if they were called separately. According to the documentation and available code examples, if one subflow fails, it can be retried based on the retry policy set for the subflow itself. To potentially rerun a subflow and let the main flow continue, you might need to handle exceptions and implement a retry mechanism within your flow definition. The test_flows.py file in the Prefect GitHub repository shows an example where a parent flow is defined with a retry, and if the first flow run fails, it is retried. However, for specific guidance on rerunning only one subflow and allowing the main flow to continue, the documentation does not provide explicit instructions. It might be necessary to use a combination of state handlers, checkpoints, and retry configurations to achieve the desired behavior. You may customize the retry behavior of a flow with the

retries

parameter like in the following example extracted from GitHub:

python
@flow(retries=1)
def parent_flow():
    # ... flow definition ...
    child_result = child_flow()
    # ... some handling for potential retries or failures ...
    return child_result

For more details, visit the linked Prefect documentation on flows and the Prefect's GitHub source code for examples of how to define retry behavior. If you require more specific assistance or examples, it may be helpful to look into the handling of retries and errors in the context of Prefect workflows.

@Marvin what i want is say subflows_01...10 and lets just say they are running sequentially. if subflow_01, 02 pass and subflows_03 fails. it believe it stop the main flow. i can re-run subflow_03 but how to i get the main flow to continue as scheduled?

To manage the continuation of your main flow after a subflow fails, you can set up your main flow to handle exceptions and potentially leverage state handlers to determine the next steps after a subflow's failure. Although the Prefect documentation on flows doesn't explicitly specify how to resume a main flow after one subflow fails and is retried, you can architect your workflow with these strategies: 1. Retries: Implement retry logic for your subflows, so they automatically attempt to run again when they encounter failures. 2. State Handlers: Utilize state handlers to customize the behavior of your flows when they transition into different states. This could mean setting a certain state on the main flow when a subflow fails, allowing you to resume the main flow after the failed subflow is retried. 3. Manual Intervention: Manually handle the resumption of your main flow by using Prefect's UI or CLI to retry the failed subflows and then resume the main flow execution. 4. Checkpoints: Use checkpoints to save the state of your workflow execution. This allows you to restart from a certain point rather than re-running successful tasks. Here's a simplified example using a state handler:

python
from prefect import flow, task
from prefect.engine.state import Failed, State

def subflow_state_handler(flow, old_state, new_state):
    if isinstance(new_state, Failed):
        # Here you can implement logic to handle the failure and resume the main flow
        # maybe even triggering a retry for the failed subflow
        pass
    return new_state

@flow
def subflow_03():
    # Subflow logic...
    pass

@flow(state_handlers=[subflow_state_handler])
def main_flow():
    # Logic before subflow_03
    result_03 = subflow_03.run()  # handle retries if necessary
    # Logic after subflow_03 - this will depend on the state handler's logic
    pass

Remember that the actual implementation will depend on your specific use case and workflow requirements. For a more customized solution, you may have to write more intricate is still needed to determine if the main flow can be designed to automatically resume after the subflow is retried successfully. If you need further examples or details, you might want to look through community forums, Prefect's GitHub issues, or consider posting a question detailing your specific use case for community assistance. For more examples of handling retries and flow states, you can refer to the Prefect GitHub's source code, and for more information on status handlers, consult the corresponding section of the Prefect documentation.