async fn spawn_flush(
batch: Batch,
limiter: &FlushLimiter,
inserter: Arc<Inserter>,
notifier: FlowNotifier,
) -> Option<JoinHandle<()>>async fn spawn_flush(
batch: Batch,
limiter: &FlushLimiter,
inserter: Arc<Inserter>,
notifier: FlowNotifier,
) -> Option<JoinHandle<()>>