fix: resolve potential race condition in JSONFileCache #2721
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The `JSONFileCache.__setitems__` function might raise a `FileExistsError` if it is run in parallel by two threads / processes: 1. Both processes discover the working dir hasn't been created yet. 2. The first process creates the working dir. 3. The second process tries to create the working dir, too and fails as it already exists. Accept this potential race — `exist_ok=True` will prevent `os.makedirs` to raise an exception. The `os.path.isdir` condition is technically no longer needed but kept keeping the change small. Furthermore, it should be slightly faster as the cache should exist most of the time.
dlm6693
previously approved these changes
Oct 3, 2022
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Thanks for your submission @msw-kialo! This looks good to me, but we need more time to review this internally.
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The
JSONFileCache.__setitems__might raise aFileExistsErrorif it isrun in parallel by two threads / processes:
as it already exists.
Accept this potential race —
exist_ok=Truewill preventos.makedirsto raise an exception.
The
os.path.isdircondition is technically no longer needed but keptkeeping the change small. Furthermore, it should be slightly faster
as the cache should exist most of the time.
The
exist_okparameter is supported since Python 3.2 / fixed in 3.4.1and therefore available in all needed python versions.