@Marvin How to add dependencies between steps? like, i have a "main_flow". this should run "extract_flow" , "load_flow" and "transform_flow" (these are calling separate tasks). how to make them depend on each other and have correct lineage?

It appears I missed specifying the search queries. Let me rectify that and find you the relevant information on handling dependencies between steps in Prefect flows. Give me a moment. To manage dependencies between tasks in Prefect, you can specify upstream dependencies which ensure tasks are executed in a particular order. This ensures your "extract", "transform", and "load" tasks operate in the correct sequence. Here’s a basic outline of how you can set this up in Prefect: In Prefect 2.x, you can define dependencies using the

wait_for

parameter, which you pass to the

.submit()

method. This approach ensures that a task will only start executing once the tasks it depends on have completed. Here's a simplified example based on Prefect 2.x:

python
from prefect import flow, task

@task
def extract_flow():
    pass

@task
def transform_flow():
    pass

@task
def load_flow():
    pass

@flow
def main_flow():
    extract_result = extract_flow.submit()
    # transform_flow depends on the completion of extract_flow
    transform_result = transform_flow.submit(wait_for=[extract_result])
    # load_flow depends on the completion of transform_flow
    load_result = load_flow.submit(wait_for=[transform_result])

In this example: -

transform_flow

waits for

extract_flow

to complete before starting. -

load_flow

waits for

transform_flow

to complete before starting. For more comprehensive details on specifying task dependencies in Prefect 2.x, you can follow this guide: Specifying Upstream Dependencies in Prefect 2.x While Prefect 3.x offers additional features like transactional semantics, these are generally more advanced and might not be necessary for the straightforward task dependency management you're looking to implement. Feel free to ask if you have more queries or if I can help you in another way!

@Marvin Is this different in prefect 3.x?

In Prefect 3.x, you continue to manage dependencies between tasks similarly to Prefect 2.x. You use task dependencies to control the execution order, ensuring that tasks run in the required sequence. Prefect 3.x also introduces more advanced features like transactional semantics. This allows you to group tasks such that they behave atomically, rolling back changes when necessary, enhancing fault tolerance and reliability. For basic task dependencies, the fundamental approach remains consistent across versions. However, Prefect 3.x enriches the framework with transactions to offer greater resilience, ensuring operations within a transaction are either fully completed or rolled back in case of failure. To explore more about transactional semantics and task dependencies in Prefect 3.x, you might want to check these links: - Transactions in Prefect 3.x - Deferred Tasks in Prefect 3.x These enhanced features are particularly useful for complex workflows but might not be necessary for simpler dependency management between flow tasks. Let me know if you need more cosmic wisdom... or if there's anything else I can help with!