* Make snapshot creation transactional
Build each snapshot in a private .incomplete-<name> staging directory
instead of mutating the final backup path directly. Any failure while
building the snapshot (hardlink failure, rsync error, or a single
Actions.ERROR entry) is now fatal: the staging directory is discarded
and BackupFailedError is raised, so a failed or interrupted backup can
never silently look like a success.
On success, the completion marker is written and the directory fsync'd
before an atomic os.rename() into the final snapshot name, so a crash
can never leave a partially-populated directory under a real snapshot
name.
Also:
- cleanup_stale_staging_dirs() removes abandoned staging directories
left by a crashed run before a new backup starts.
- _reserve_snapshot_name() avoids same-second snapshot name collisions.
- cli.py releases the backup lock in finally and returns a nonzero
exit code when BackupFailedError is raised.
Updates the error-recovery tests that previously asserted failures
were swallowed silently to assert BackupFailedError is raised instead,
matching the new fail-loud contract.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
* Address Copilot review feedback on transactional snapshots
- Remove unused uuid import.
- _reserve_snapshot_name() also checks for a collision with an existing
.incomplete-<name> staging directory, not just the final snapshot
name.
- _fsync_dir() opens with O_DIRECTORY where available.
- Fsync the completion marker file itself, and fsync the parent
backups_dir after the rename, so the marker and the rename survive a
crash/power loss.
- Re-raise an already-BackupFailedError unchanged (preserving its
traceback) instead of wrapping it in a new instance; only
fs.BackupCreationError gets wrapped.
- Wrap the initial os.mkdir(staging.path) failure in BackupFailedError
so every failure path uses the documented exception.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
---------
Co-authored-by: Maxim Shulga <maxim.shulga@alludo.com>
Co-authored-by: Claude Sonnet 5 <noreply@anthropic.com>
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