用于管控业务对 mysql 集群的访问
读写分离
权限管控
分组功能支持
流量负载均衡
账号管理
配置热加载

客户端请求类型对应协议说明：
COM_QUIT 关闭连接 handleRollback()
Close() https://dev.mysql.com/doc/dev/mysql-server/latest/page_protocol_com_quit.html
COM_QUERY SQL查询及 dml、ddl请求 handleQuery() https://dev.mysql.com/doc/dev/mysql-server/latest/page_protocol_com_query.html
COM_PING 测试连通性 writeOK() https://dev.mysql.com/doc/dev/mysql-server/latest/page_protocol_com_ping.html
COM_INIT_DB 切换数据库 handleUseDB() https://dev.mysql.com/doc/dev/mysql-server/latest/page_protocol_com_init_db.html
COM_FIELD_LIST 获取数据表字段信息 handleFieldList() https://dev.mysql.com/doc/dev/mysql-server/latest/page_protocol_com_field_list.html
COM_STMT_PREPARE 预处理SQL语句 handleStmtPrepare() https://dev.mysql.com/doc/dev/mysql-server/latest/page_protocol_com_stmt_prepare.html
COM_STMT_EXECUTE 执行预处理语句 handleStmtExecute() https://dev.mysql.com/doc/dev/mysql-server/latest/page_protocol_com_stmt_execute.html
COM_STMT_CLOSE 销毁预处理语句 handleStmtClose() https://dev.mysql.com/doc/dev/mysql-server/latest/page_protocol_com_stmt_close.html
COM_STMT_SEND_LONG_DATA 发送BLOB类型的数据 handleStmtSendLongData() https://dev.mysql.com/doc/dev/mysql-server/latest/page_protocol_com_stmt_send_long_data.html
COM_STMT_RESET 清除预处理语句参数缓存 handleStmtReset() https://dev.mysql.com/doc/dev/mysql-server/latest/page_protocol_com_stmt_reset.html
COM_SET_OPTION 设置语句选项 handleSetOption() https://dev.mysql.com/doc/dev/mysql-server/latest/page_protocol_com_set_option.html