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I have a flow that runs locally but is returning a None result when run in Prefect Cloud. I think it...
# ask-community
j
I have a flow that runs locally but is returning a None result when run in Prefect Cloud. I think it's because I'm not setting the S3Result as the default? But this is confusing since I'm using the S3Storage as the default for flow storage. Does this seem right?
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Updated
9 May 2022 2:31pm
Result Type
Result
Result Location
None
k
Are you printing inside the flow block?
j
Yes - the individual task is fairly plain, and seems to return a result with the local flow:
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@task(name="Extract Owners from Streamline")
def extract_owners() -> DataFrame:
    """
    Grab Owners from Streamline and serialize as a Pandas DataFrame.
    """

    logger = prefect.context.get("logger")
    streamline = Streamline(token_key=TOKEN_KEY, token_secret=TOKEN_SECRET)
    owners_df: DataFrame = streamline.get_owners()

    if owners_df.empty:
        raise FAIL(
            "Owners DataFrame is empty. Something is wrong with the API pull from Streamline."
        )

    <http://logger.info|logger.info>(f"Pulled {owners_df.shape[0]} owners for {FLOW_NAME}")

    return owners_df
So within the Flow() as flow context, it's fed like this (perhaps incorrectly?):
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owners_df = extract_owners()

    load_owners_s3(owners_df, database=glue_database)
When it reaches 
load_owners_s3
, it's a Nonetype, which raises the appropriate error with aws-data-wrangler: wr.s3.to_parquet.
Oh, sorry Kevin, I misread your reply. I'm not printing, that info on the None result from Prefect Cloud for the specific Task.
I must have something misconfigured. Earlier info in #CL09KU1K7 suggests that:
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by default, when you use e.g. S3 storage, Prefect will use S3 also for results automatically, unless you explicitly turn off checkpointing
k
Wait, that thing you mentioned is more Prefect 2.0 I think
Is it none for a new flow run, or when restarting from failure?
j
New flow run: I'm on Prefect 1-series still
That is when trying to explicitly set S3Result on the result for the flow, too.
So the nonetype fails the subsequent task
k
What is the log of the shape?
j
Oh, interesting. S3Result forced it to produce .prefect_results after the task finished. I spoke too quickly.
k
This looks right. Are you sure the issue is not with 
glue_database
?
j
No, glue-database is good. I think the current issue (separate from the original post) is now that the prefectTaskRole doesn't have access to the S3 bucket that I was testing locally to serialize the Parquet files too, but that's an easy fix to the IAM role.
So I think, at least with my setup, that it is necessary to explicitly pass in S3Result then
k
The Result should not affect whether or not the return from a task is None
It gets persisted but it still gets fed in memory to the next task
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