@Override
  public List<WALNode> getNodesSnapshot() {
    List<WALNode> snapshot;
    nodesLock.lock();
    try {
      snapshot = new ArrayList<>(walNodes);
    } finally {
      nodesLock.unlock();
    }
    return snapshot;
  }
This strategy creates wal nodes according to the number of memTables. Each wal node manages fixed
number of memTables.
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/storageengine/dataregion/wal/allocation/ElasticStrategy.java