code: private Long findServerId(MysqlConnection mysqlConnection) {
          try {
              ResultSetPacket packet = mysqlConnection.query("show variables like 'server_id'");
              List<String> fields = packet.getFieldValues();
              if (CollectionUtils.isEmpty(fields)) {
                  throw new CanalParseException("command : show variables like 'server_id' has an error! pls check. you need (at least one of) the SUPER,REPLICATION CLIENT privilege(s) for this operation");
              }
              return Long.valueOf(fields.get(1));
          } catch (IOException e) {
              throw new CanalParseException("command : show variables like 'server_id' has an error!", e);
          }
      }
docs: 查询当前db的serverId信息