#36997: test_double_replaced_migrations_are_checked_correctly fails
intermittently
under Windows Subsystem for Linux (WSL)
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Reporter: Stewart Matheson | Owner: (none)
Type: Bug | Status: closed
Component: Migrations | Version: dev
Severity: Normal | Resolution: needsinfo
Keywords: | Triage Stage: Unreviewed
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
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Comment (by Stewart Matheson):
The issue relates is a file system a race condition that is most likely
being triggered by the unpredictable timings of the filesystem running
under HyperV and WSL. After the test writes the first migration file to
the /tmp folder there is a chance that the filesystem mtime update is
still waiting in the FS journal. When the migration system performs a
second read its reading the filesystem before the mtime has been updated
from the previous write. Because of this timing python's file cache is not
invalidated when the test expects it to be. The result is that the first
migration will be over written and the test will fail when it attempts to
squash migrations that don't exist because they where never written in the
first place.
Running the same test on bare metal linux, docker linux or macos is
unlikely to trigger this issue is their filesystems have timings that are
more predictable than WSL.
Running
{{{
importlib.invalidate_caches()
}}}
Each time after a migration file is written resolves this issue for me as
python will bypass reading the mtime. Given all that I'm not too sure how
you would reproduce this as I would have thought other WSL users would be
running in to this issue.
--
Ticket URL: <https://code.djangoproject.com/ticket/36997#comment:2>
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