<@ULVA73B9P> How can I programmatically detect if a prefect flow is a subflow from within a subflow ...

Tejaswi Bhangi

05/31/2024, 4:03 AM

@Marvin How can I programmatically detect if a prefect flow is a subflow from within a subflow or a task called by that subflow?

Marvin

05/31/2024, 4:03 AM

To programmatically detect if a flow is a subflow or if a task is called by a subflow within Prefect, you can look at the

state_details

of the flow or task run. Specifically: - A task that represents a subflow will have a

child_flow_run_id

field in its

state_details

. - A subflow can be identified by the presence of a

parent_task_run_id

in its

state_details

. Here's an example of how you might implement this in Prefect:

Copy code

python
from prefect import flow, task, get_run_context

@task
def detect_if_subflow():
    context = get_run_context()
    if context.flow_run.state_details.parent_task_run_id:
        print("This flow is a subflow.")
    else:
        print("This flow is not a subflow.")

@flow
def subflow_example():
    detect_if_subflow()

@flow
def parent_flow():
    subflow_example()

if __name__ == "__main__":
    parent_flow()

In this example: 1. The

detect_if_subflow

task checks the

state_details

of the current flow run to see if it has a

parent_task_run_id

. 2. If

parent_task_run_id

is present, it indicates that the current flow is a subflow. For more details, you can refer to the Prefect documentation on flows. Happy subflow detecting! Or as happy as one can be in the vast, incomprehensible universe. Is there anything else you need?

Tejaswi Bhangi

05/31/2024, 4:06 AM

@Marvin That failed with this error: File "/workspace/.venv/lib/python3.10/site-packages/prefect/_internal/concurrency/calls.py", line 352, in _run_sync result = self.fn(*self.args, **self.kwargs) File "/workspace/gpt_candidate/v2/setup.py", line 83, in setup_telemetry job_id = flow_run.get_parent_flow_run_id() if detect_if_subflow() else flow_run.get_id() File "/workspace/gpt_candidate/v2/setup.py", line 77, in detect_if_subflow if context.flow_run.state_details.parent_task_run_id: AttributeError: 'TaskRunContext' object has no attribute 'flow_run' I need to be able to call the "detect_if_subflow" function from within a task called by the subflow.

Marvin

05/31/2024, 4:06 AM

Based on the updated information, it appears that in Prefect, you should explicitly obtain the flow run context and access its state details to check if it is a subflow from within a task. Here's how you can do it within a task: 1. Access the Flow Run Context: Use

FlowRunContext.get()

to retrieve the flow run context explicitly. 2. Check for
parent_task_run_id
: Look for the

parent_task_run_id

in the flow run's

state_details

to determine if it's a subflow. Here is the corrected implementation:

Copy code

python
from prefect import flow, task
from prefect.context import FlowRunContext

@task
def detect_if_subflow():
    flow_run_ctx = FlowRunContext.get()
    if flow_run_ctx and flow_run_ctx.state_details.parent_task_run_id:
        print("This flow is a subflow.")
        return True
    else:
        print("This flow is not a subflow.")
        return False

@flow
def subflow_example():
    detect_if_subflow()

@flow
def parent_flow():
    subflow_example()

if __name__ == "__main__":
    parent_flow()

This implementation ensures that from within the

detect_if_subflow

task, you correctly access the flow run context and its state details. With this approach, you should be able to detect if the flow is a subflow even when the task is called by a subflow. For more guidance, refer to the Prefect documentation on runtime contexts which provides further details on these concepts.

Tejaswi Bhangi

05/31/2024, 4:10 AM

@Marvin Got this error trying that: AttributeError: 'EngineContext' object has no attribute 'state_details' Again, I need to be able to call "detect_is_subflow" from a prefect task

Marvin

05/31/2024, 4:10 AM

To programmatically detect if a flow is a subflow from within a

task

in Prefect, you need to check the

parent_task_run_id

of the flow run context. Here’s the corrected implementation taking into account that

TaskRunContext

doesn't support

state_details

. Instead, we're going to focus on retrieving the

flow_run

context: 1. Access the Task Run Context: Use

get_run_context()

to retrieve the context. 2. Check for Parent Flow Attributes: Determine from the

parent_task_run_id

if this flow is part of a subflow. Here is an example:

Copy code

python
from prefect import flow, task, get_run_context
from prefect.context import FlowRunContext, TaskRunContext

@task
def detect_if_subflow():
    context = get_run_context()
    if isinstance(context, TaskRunContext):
        flow_run = context.task_run.flow_run
        if flow_run.parent_task_run_id:
            print("This flow is a subflow.")
            return True
        else:
            print("This flow is not a subflow.")
            return False
    else:
        print("Context is not a TaskRunContext.")
        return False

@flow
def subflow_example():
    detect_if_subflow()

@flow
def parent_flow():
    subflow_example()

if __name__ == "__main__":
    parent_flow()

In this example: 1. Access Run Context: The

get_run_context()

function is used to access the current run context. 2. Check Parent Flow ID: Within the

TaskRunContext

, check the associated `flow_run`'s

parent_task_run_id

to see if this is a subflow. Running this code should allow you to programmatically detect if a flow is a subflow from within a task. For reference, check the Prefect documentation on runtime contexts for additional information. Let me know if there's anything else you'd like to dive into!

Tejaswi Bhangi

05/31/2024, 4:13 AM

@Marvin Getting this now: AttributeError: 'TaskRun' object has no attribute 'flow_run'. Did you mean: 'flow_run_id'?

Marvin

05/31/2024, 4:13 AM

It appears that accessing the flow run from the task run context is slightly different. Instead, you should use the

flow_run_id

to fetch the flow run details. Here is a refined approach: 1. Access the Task Run Context: Use

get_run_context()

to retrieve the context. 2. Fetch Flow Run Details: Use the Prefect client to retrieve the flow run details using the

flow_run_id

. Here's the updated implementation:

Copy code

python
from prefect import flow, task, get_run_context
from prefect.client import get_client

@task
async def detect_if_subflow():
    context = get_run_context()
    if context:
        task_run = context.task_run
        flow_run_id = task_run.flow_run_id
    
        async with get_client() as client:
            flow_run = await client.read_flow_run(flow_run_id)
        
        if flow_run.parent_task_run_id:
            print("This flow is a subflow.")
            return True
        else:
            print("This flow is not a subflow.")
            return False
    else:
        print("No context available.")
        return False

@flow
def subflow_example():
    detect_if_subflow()

@flow
def parent_flow():
    subflow_example()

if __name__ == "__main__":
    parent_flow()

In this corrected code: 1. Access Run Context: Using

get_run_context()

, you access the current context. 2. Fetch Contextual Data: Retrieve the

flow_run_id

from the

task_run

context. 3. Prefect Client: Use the Prefect client to read the flow run details by

flow_run_id

. 4. Check for Parent ID: Check if the

parent_task_run_id

is present to determine if this is a subflow. This solution should work seamlessly for detecting if a flow is a subflow within a task. For further details, you might consult the Prefect API documentation.

Tejaswi Bhangi

05/31/2024, 4:59 AM

Nevermind, this works:

Copy code

job_id = flow_run.parent_flow_run_id if flow_run.parent_flow_run_id else flow_run.id

I forgot to decorate my parent flow facepalm

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