benbjohnson/litestream · info

hash temp name: %w

Error message

hash temp name: %w

What it means

tempFilenameFromCanonical appends an FNV-64a hash of the canonical name to the temp file base to keep names deterministic and collision-free. This error wraps a failure from hash.Write. In practice hash.Hash Write on a pure in-memory implementation never fails, so this error is effectively unreachable defensive code, but the API surface requires handling the error return.

Source

Thrown at vfs.go:384

	if name == "" {
		return ""
	}
	name = filepath.Clean(name)
	if name == "." || name == string(filepath.Separator) {
		return ""
	}
	return name
}

func tempFilenameFromCanonical(canonical string) (string, error) {
	base := filepath.Base(canonical)
	if base == "." || base == string(filepath.Separator) {
		return "", fmt.Errorf("invalid temp file name: %q", canonical)
	}

	h := fnv.New64a()
	if _, err := h.Write([]byte(canonical)); err != nil {
		return "", fmt.Errorf("hash temp name: %w", err)
	}
	return fmt.Sprintf("%s-%016x", base, h.Sum64()), nil
}

func (vfs *VFS) openTempFile(name string, flags sqlite3vfs.OpenFlag) (sqlite3vfs.File, sqlite3vfs.OpenFlag, error) {
	dir, err := vfs.ensureTempDir()
	if err != nil {
		return nil, flags, err
	}
	deleteOnClose := flags&sqlite3vfs.OpenDeleteOnClose != 0 || name == ""
	var f *os.File
	var onClose func()
	if name == "" {
		f, err = os.CreateTemp(dir, "temp-*")
		if err != nil {
			return nil, flags, sqlite3vfs.CantOpenError
		}
	} else {

View on GitHub (pinned to 4ed7a308f6)

Solutions

1. No action needed — this is defensive error handling of an infallible in-memory hash write.
2. If it ever appears, check for exotic build tags or a replaced hash implementation in the module graph.

if err != nil && strings.Contains(err.Error(), "hash temp name") {
    // unreachable with stdlib fnv; treat as a bug and report
}

When it happens

Trigger: Called from openTempFile for every temp/transient/journal file open; would only surface if fnv.New64a's Write returned a non-nil error, which does not occur with the standard library implementation.

Common situations: Developers seeing this in code review or coverage reports; practically never encountered at runtime by users.

Understand the failure class

Background: "This is a bug, please report it": internal invariant violations, unreachable panics, and SNH errors explained — this error's family across 47 libraries.

Related errors

• create temp dir for hydration: %w
• cannot delete vfs file
• invalid temp file name: %q
• temp file not tracked
• clear write buffer: %w

AI-assisted analysis of benbjohnson/litestream@4ed7a308f6 (2026-09-06). Data as JSON: /api/errors/f02384650f5313e5. Report an issue: GitHub.