RyanCodrai/turbovec · warning

{path} was written and committed, but syncing its parent dir

Error message

{path} was written and committed, but syncing its parent directory failed ({e}); the file is visible now but the rename may not survive power loss

What it means

After committing an index file, sync_parent_dir_after_commit calls sync_parent_dir to fsync the containing directory so the rename/new file survives power loss; this is unsupported or failing on some platforms/filesystems (issue #365). The failure is reported as a non-fatal warning via crate::warning rather than an error — the data is written and visible, only durability of the directory entry is in question.

Source

Thrown at turbovec/src/io.rs:495

    Ok(())
}

/// Run the post-rename parent-directory fsync, which cannot fail the save.
///
/// The rename is the commit point: once it returns, the new file is the
/// one readers see and the temp name is gone. A failure of the directory
/// fsync *after* that point is a durability shortfall on an
/// already-committed file, not a failed save — reporting it as `Err`
/// would tell a caller its previous file is still in place when it is
/// not, sending retry/rollback policies down a destructive path, and the
/// error cleanup would then try to unlink a temp name that no longer
/// exists (#365). So the save succeeds and the shortfall is reported as
/// a non-fatal diagnostic through [`crate::warning`], which an embedder
/// can route into its own logging (or silence) instead of being handed
/// an unconditional line on stderr.
pub(crate) fn sync_parent_dir_after_commit(path: &Path) {
    if let Err(e) = sync_parent_dir(path) {
        crate::warning::warn(&format!(
            "{} was written and committed, but syncing its parent directory \
             failed ({e}); the file is visible now but the rename may not \
             survive power loss",
            path.display(),
        ));
    }
}

View on GitHub (pinned to ccab9f325e)

Solutions

1. Treat it as a diagnostic: the file was written; verify durability requirements per platform
2. Save to a local filesystem that supports directory fsync
3. Silence/route the warning via the crate::warning hook if durability is handled elsewhere (e.g. snapshotting FS)
4. Copy the file and re-save after confirming the parent dir is syncable

Example fix

// before
idx.save("/mnt/nfs/index.tv")?; // warns: parent dir sync failed
// after
crate::warning::set_handler(|w| log::debug!("{}", w)); // or:
idx.save("/var/lib/app/index.tv")?; // local fs, dir fsync works

# ensure the destination filesystem supports directory fsync before saving
import os
if os.statvfs(save_path).f_bsize and save_path.startswith(("/mnt/", "/net/")):
    logging.warning("saving to network fs; parent-dir sync may fail")

def is_local_fs(path: str) -> bool:
    import os
    return not path.startswith(("/mnt/", "/net/", "//"))  # rough heuristic
# guard: is_local_fs(save_path) before idx.save(save_path)

import warnings
with warnings.catch_warnings(record=True) as caught:
    idx.save(path)
durability_warnings = [w for w in caught if "parent directory" in str(w.message)]
if durability_warnings:
    logging.warning("file written but directory fsync failed: %s", durability_warnings)

When it happens

Trigger: Saving/committing an index on a filesystem or platform where fsync on a directory fd fails (e.g. some Windows or network filesystems), during any save/sync commit path.

Common situations: Saving to network mounts (NFS/SMB), unusual container filesystems, or Windows where directory fsync is unavailable.

Understand the failure class

Background: "failed to write file", "Could not save figure", "Error saving remote file" — file write failed: causes and fixes across languages and libraries — this error's family across 38 libraries.

Related errors

• {src}: the newest commit (generation {newest}) is incomplete
• {} {detail}.
• truncated file
• file too large for this platform
• similarity='dot_product' produces unbounded raw inner produc

AI-assisted analysis of RyanCodrai/turbovec@ccab9f325e (2026-09-06). Data as JSON: /api/errors/d812e1148e55c26e. Report an issue: GitHub.