public static CnToDnInternalServiceAsyncRequestManager getInstance() {
    return ClientPoolHolder.INSTANCE;
  }
Asynchronously send RPC requests to DataNodes. See queryengine.thrift for more details.
iotdb-core/confignode/src/main/java/org/apache/iotdb/confignode/client/async/CnToDnInternalServiceAsyncRequestManager.java