Datasets use atomic write when persisting to disk #307
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Partially fixes: #1954 Prior to this change dataset.download() would use a normal file write to persist downloaded data to disk. This meant another process or thread could check for the file and attempt to read it before the full content was written. This change uses a temporary file + a rename to update the file atomically. If a process is already reading a file that the new verion overwrites, the previous file node is unlinked rather than being overwritten so the read will work as expected. This will allow us to back out optimistically pre-loading dataset data before it is needed (and causing 404 errors when running tests on machines without the appropriate permissions to download UK data)
nikhilwoodruff
approved these changes
Nov 11, 2024
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Partially fixes PolicyEngine/policyengine-api#1954
Prior to this change dataset.download() would use a normal file write to persist downloaded data to disk.
This meant another process or thread could check for the file and attempt to read it before the full content was written.
This change uses a temporary file + a rename to update the file atomically.
If a process is already reading a file that the new verion overwrites, the previous file node is unlinked rather than being overwritten so the read will work as expected.
This will allow us to back out optimistically pre-loading dataset data before it is needed (and causing 404 errors when running tests on machines without the appropriate permissions to download UK data)
Thanks for contributing! Please remove any top-level sections that do not apply to your changes.
make format && make documentationhas been run.New variable
What's changed
See description in the commit above
Bug fix
What this fixes and how it's fixed
See description in commit above