@Override
  public synchronized ListenableFuture<?> isFull() {
    checkState();
    // blocked could be null if this channel is closed before it is opened by ShuffleSinkHandle
    // return immediateVoidFuture() to avoid NPE
    if (closed) {
      return immediateVoidFuture();
    }
    return nonCancellationPropagating(blocked);
  }
max bytes this SinkChannel can reserve.
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/queryengine/execution/exchange/sink/SinkChannel.java