pub fn append_locked(root: &Path, path: &Path, line: &str) -> Option<()>Expand description
Append a line that is too large for one atomic write(2), serialising
against other writers with the compaction lock instead.
Only the dry-run sink uses this: a whole batch does not fit under
PIPE_BUF, and the flush path is neither the panic hook nor the signal
handler, so a non-blocking try_write is safe there. On contention the
batch is dropped, which is the same fail-open behavior as a failed POST.