Task Run Fails to Read Upstream Result the First Time a Flow is Run on Windows

[dylanbhughes]

Description

it seems that the file is either getting cleaned up OR reading from the file has a bug that is specific to windows paths

Expected Behavior

Result is read properly

Reproduction

Environment

Windows

[cicdw]

@dylanbhughes I am unable to reproduce on a Windows machine; I'll need some example code + configuration. Note that this could happen if you are using caching (cache_for) across multiple machines with a LocalResult

[cicdw]

OK after attempting to reproduce this in a few different ways, I've concluded that something external to Prefect must have deleted this file. Based on the traceback, it's clear this Task used caching, and the non-existence of the file meant that this particular Cached state could not be used.

I do think Prefect should have more gracefully handled this situation by logging a warning that we were unable to read the result and therefore will not be using that particular cache. There's no reason to fail the execution of the task here, because nonexistence of the file is equivalent to the cache being invalid IMO. Leaving this ticket open to track this UX enhancement.