fn spawn_maintenance_loop(
hummock_manager: Arc<HummockManager>,
backup_manager: Option<BackupManagerRef>,
shutdown_rx: Receiver<bool>,
) -> JoinHandle<()>fn spawn_maintenance_loop(
hummock_manager: Arc<HummockManager>,
backup_manager: Option<BackupManagerRef>,
shutdown_rx: Receiver<bool>,
) -> JoinHandle<()>