public static WALFakeNode getFailureInstance(Exception e) {
    return new WALFakeNode(
        Status.FAILURE, new WALException("Cannot write wal into a fake node. ", e));
  }
This class provides fake wal node when wal is disabled or exception happens.
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/storageengine/dataregion/wal/node/WALFakeNode.java