@Override
  protected File rollLogWriter(long searchIndex, WALFileStatus fileStatus) throws IOException {
    File file = super.rollLogWriter(searchIndex, fileStatus);
    currentWALFileWriter.setCompressedByteBuffer(compressedByteBuffer);
    return file;
  }
two buffers switch between three statuses (there is always 1 buffer working).
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/storageengine/dataregion/wal/buffer/WALBuffer.java