private String getBackend() throws IOException {
        try {
            // get be url from fe
            return RestService.randomBackend(options, readOptions, LOG);
        } catch (IOException | DorisException e) {
            LOG.error("get backends info fail");
            throw new IOException(e);
        }
    }
format data to csv or json

@param values
@param format
@return string
@throws JsonProcessingException
inlong-sort/sort-flink/sort-flink-v1.13/sort-connectors/doris/src/main/java/org/apache/inlong/sort/doris/table/DorisDynamicSchemaOutputFormat.java