Attempt to fix race conditions with non-atomic file copy for worker jars #90
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We were copying a file used by multiple threads directly to its destination. Problem is that copying is not an atomic action, so we could end up in states where the file wasn't correct when it was used. This should avoid that issue by first copying the file to a temp file and then using an atomic move to move the file to the destination used by other threads.
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| Files.createDirectories(workerJar.getParent()) | ||
| Files.copy(workRequestJar, workerJar) | ||
| Files.move(tmpWorkerJar.get, workerJar, StandardCopyOption.ATOMIC_MOVE) |
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ATOMIC_MOVE: ... If the target file exists then it is implementation specific if the existing file is replaced or this method fails by throwing an IOException (documentation)
Do you know what happens on our systems? Does it replace or throw an error?
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I do not know. REPLACE_EXISTING is not set, so I'm hoping it would throw an error.
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That documentation also states for ATOMIC_MOVE:
The move is performed as an atomic file system operation and all other options are ignored.
so I don't think it matters if REPLACE_EXISTING is set or not, it may or may not throw an error.
jadenPete
approved these changes
Apr 8, 2025
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Closing in favor of #91 |
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We were copying a file used by multiple threads directly to its destination. Problem is that copying is not an atomic action, so we could end up in states where the file wasn't correct when it was used.
This should avoid that issue by first copying the file to a temp file and then using an atomic move to move the file to the destination used by other threads.