@Override
  public void onSessionLoopError(Throwable throwable) {
    LOGGER.warn(
        "onSessionLoopError: {}",
        throwable.getMessage() == null ? "null" : throwable.getMessage(),
        throwable);
  }
PublishHandler handle the messages from MQTT clients.
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/pipe/extractor/mqtt/MQTTPublishHandler.java