set_maintenance_mode should use atomic write.

[reitermarkus]

Python version

any

Django version

any

Package version

any

Current behavior (bug description)

set_maintenance_mode uses normal write, i.e open + write, which may result in a race condition as seen in inventree/InvenTree#6066. An empty maintenance_mode.txt then leads to a state value is not 0|1 error.

Expected behavior

set_maintenance_mode uses atomic write, i.e. open + write to temporary file, then mv temporary file to actual file. I'm sure there is a Python package that provides such a function.

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[fabiocaccamo]

@reitermarkus thank you for reporting this issue.

[fabiocaccamo]

Depends on fabiocaccamo/python-fsutil#91

[fabiocaccamo]

@reitermarkus fixed in 0.21.0 version.

[reitermarkus]

Thanks! Although I would remove

fabiocaccamo/python-fsutil@6c8a58b#diff-d82a200cf6742866f0d549f5bd4a22416ef6cdbcc1cde15c6b32c64f2663fe70R1330

since this can again have the same race condition and pollute user directories with temporary files.

[fabiocaccamo]

@reitermarkus for the temp file directory I used the same file directory to ensure that the temporary file is created on the same filesystem of the final file and guarantee atomicity of the replace operation, otherwise there is a potential risk of data corruption or loss.

What do you think is best to do here?

[reitermarkus]

Given that the state can only be 0/1, maybe change to simply checking the existence instead of the contents of the file.

[fabiocaccamo]

The local file backend uses the same logic as the other backends.

[fabiocaccamo]

@reitermarkus check fabiocaccamo/python-fsutil@11fbc5e