一般情况下，报too many connections，是linux服务器登录不上mysql，navicat也登录不上mysql，所以我们只能重新启动mysql：
service mysqld restart
启动后：临时解决too many connections办法是：
登录linux服务器， 进入MySQL数据库：
查询最大连接数：
select VARIABLE_VALUE from information_schema.GLOBAL_VARIABLES where VARIABLE_NAME='MAX_CONNECTIONS';
报错：ERROR 3167 (HY000): The 'INFORMATION_SCHEMA.GLOBAL_VARIABLES' feature is disabled; see the documentation for 'show_compatibility_56'
--从mysql5.7.6开始information_schema.global_status已经开始被舍弃，为了兼容性，此时需要打开 show_compatibility_56
MySQL> select * from information_schema.global_status limit 3;
ERROR 3167 (HY000): The 'INFORMATION_SCHEMA.GLOBAL_STATUS' feature is disabled; see the documentation for 'show_compatibility_56'
--查看show_compatibility_56其值
mysql> show variables like '%show_compatibility_56%';
+-----------------------+-------+
| Variable_name | Value |
+-----------------------+-------+
| show_compatibility_56 | OFF |
+-----------------------+-------+
1 row in set (0.01 sec)
--把show_compatibility_56打开
mysql> set global show_compatibility_56=on;
Query OK, 0 rows affected (0.00 sec)
mysql> show variables like '%show_compatibility_56%';
+-----------------------+-------+
| Variable_name | Value |
+-----------------------+-------+
| show_compatibility_56 | ON |
+-----------------------+-------+
1 row in set (0.00 sec)
mysql> select * from information_schema.global_status limit 3;
+-----------------------+----------------+
| VARIABLE_NAME | VARIABLE_VALUE |
+-----------------------+----------------+
| ABORTED_CLIENTS | 0 |
| ABORTED_CONNECTS | 0 |
| BINLOG_CACHE_DISK_USE | 0 |
+-----------------------+----------------+
3 rows in set, 1 warning (0.00 sec)
完成上述操作后，即可用mysql_front连接到mysql数据库了，可以对数据库进行图形化的界面操作~
修改最大连接数：
执行以下语句修改最大连接数：set global max_connections = 3600;
永久性的修改：
找到 my.cnf 修改配置文件
然后，重新启动mysql: service mysqld restart