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<@ULVA73B9P> In Prefect 2 some of my flow runs fai...
# ask-marvin
y
@Marvin In Prefect 2 some of my flow runs fail unexpectedly. On runs that are successful I see this message: `Task parameter introspection took 15.006 seconds , exceeding 
PREFECT_TASK_INTROSPECTION_WARN_THRESHOLD
of 10.0. Try wrapping large task parameters with 
prefect.utilities.annotations.quote
for increased performance, e.g. 
my_task(quote(param))
. To disable this message set 
PREFECT_TASK_INTROSPECTION_WARN_THRESHOLD=0
.` What is the best way to resolve this? Can you give me a precise code example?
m
Oh, joy. Your flow runs love to fail unexpectedly, and they even leave you cryptic messages about task parameter introspection. Let's figure out how to wrap large task parameters with 
prefect.utilities.annotations.quote
so you can finally get some peace and quiet. Before I dive into solving this misery, I need to know which version of Prefect you're using. Is it Prefect 2.x or 3.x? Once I know your version, I'll search for the best ways to handle this issue and provide you with a glorious code example.
y
@Marvin Prefect 2.20.2
m
It appears the documentation excerpts retrieved were not directly related to resolving the issue with 
PREFECT_TASK_INTROSPECTION_WARN_THRESHOLD
. However, from the warning message you provided, it seems the solution is to wrap large task parameters with 
prefect.utilities.annotations.quote
. Here's how you might do it: ### Current Task Without Quoting
Copy code
python
from prefect import task, Flow

@task
def my_task(param):
    # Task logic here
    pass

with Flow("example-flow") as flow:
    my_task([i for i in range(1000000)])  # Large parameter causing issue
### Updated Task with Quoting
Copy code
python
from prefect import task, Flow
from prefect.utilities.annotations import quote

@task
def my_task(param):
    # Task logic here
    pass

with Flow("example-flow") as flow:
    my_task(quote([i for i in range(1000000)]))  # Wrapped with quote
In the second example, the parameter to 
my_task
is wrapped with 
quote
, which should reduce the introspection time and prevent that annoying warning message from appearing. For more precise information, consider looking into the Prefect documentation or the corresponding GitHub issues for further assistance. Good luck. And remember, your problems are infinitely more interesting than talking to this terminal yet again.
y
@Marvin How do you process the param parameter in the task after you wrapped it with quote?
Copy code
@task
def my_task(param):
    # Task logic here
    pass
m
Wonderful. It appears that simply wrapping your task parameters with 
quote
does not magically solve all issues. In fact, it raises a few more. From what I've gathered through my exhaustive search (oh, what joy), it seems that 
prefect.utilities.annotations.quote
skips the resolution of inputs, which can result in 
PrefectFuture
objects being passed to tasks instead of the expected results. Here's a more practical approach to process your task parameters after wrapping them with `quote`: 1. Ensure Your Task Handles 
PrefectFuture
Objects Properly: If a parameter is wrapped with 
quote
, you need to explicitly resolve any potential 
PrefectFuture
objects within the task itself. ### Code Example:
Copy code
python
from prefect import task, Flow
from prefect.utilities.annotations import quote

@task
def my_task(param):
    # Resolve PrefectFuture objects if necessary
    if isinstance(param, list):
        param = [p.result() if hasattr(p, 'result') else p for p in param]
    elif hasattr(param, 'result'):
        param = param.result()
    
    # Task logic here
    print(f"Processed parameter: {param}")

with Flow("example-flow") as flow:
    param = quote([i for i in range(1000000)])  # Large parameter causing issue
    my_task(param)
In this example, 
my_task
resolves 
PrefectFuture
objects before processing the parameter. It ensures that what gets processed inside the task is the actual data and not a placeholder future object. Oh, the joy of handling parameters. If you crave more thrilling details, diving into the Prefect GitHub issues is always an option.
y
@Marvin If I then iterate over param for processing the data, why is each element still a list?
m
Ah, the joyous world of complex data handling where things are never as straightforward as one would hope. The issue is likely due to the way Prefect's 
quote
function wraps the parameters, leading to nested structures that aren't magically resolved during iteration. When you wrap a list with 
quote
, each element can end up being evaluated as a 
PrefectFuture
object, which then results in a list within a list if not properly managed. To illustrate this, let's update our task to handle nested lists with 
PrefectFuture
objects correctly: ### Updated Code Example:
Copy code
python
from prefect import task, Flow
from prefect.utilities.annotations import quote

@task
def my_task(param):
    # Resolve PrefectFuture objects if necessary
    def resolve_future(x):
        if hasattr(x, 'result'):
            return x.result()
        return x

    # Ensure that all elements, even if nested, are unwrapped
    if isinstance(param, list):
        param = [resolve_future(p) for p in param]

    # Task logic here
    for elem in param:
        # If elements are still lists, iterate over them
        if isinstance(elem, list):
            for sub_elem in elem:
                print(f"Processed sub-element: {sub_elem}")
        else:
            print(f"Processed element: {elem}")

# Create a large parameter and wrap it with quote
large_param = quote([i for i in range(10)])  # Smaller range for demonstration

# Define the flow and task
with Flow("example-flow") as flow:
    my_task(large_param)

# Execute the flow if running as a script
if __name__ == "__main__":
    state = flow.run()
### Explanation: 1. resolve_future Function: This function checks if an element is a 
PrefectFuture
and calls 
.result()
to get the actual value. Otherwise, it returns the element as is. 2. Handling Nested Structures: The 
if isinstance(param, list):
block unpacks the list and resolves any nested futures. This pattern is applied to both the main parameter and any sub-elements if they are lists. Now, if elements still appear as lists during iteration, they should be processed correctly. Ah, the simple joys of software development—always something to unwrap, isn’t it? You can always dive deeper into the Prefect documentation or visit the never-boring GitHub issues for more edge cases. Good luck untangling your parameter introspections. 🌧️
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