ERROR 1040 (08004): Too many connections

ERROR 1040 (08004): Too many connections

　　长期一来，mysql低版本中，当面对连接数陡增而出现too many connections时，往往比较棘手。今天特意在mysql社版本的8.0.17中，操作试验并记录下了。以前percona版本中就有该功能了。以后再也不用重启服务了。

mysql> show variables like '%max_conn%';
+------------------------+---------+
| Variable_name          | Value   |
+------------------------+---------+
| max_connect_errors     | 1000000 |
| max_connections        | 1024    |
| mysqlx_max_connections | 100     |
+------------------------+---------+
3 rows in set (0.00 sec)

mysql> set global max_connections=2;
Query OK, 0 rows affected (0.00 sec)

# 管理端口

mysql> show variables like '%port%';
+--------------------------+-------+
| Variable_name            | Value |
+--------------------------+-------+
| admin_port               | 33062 |
| large_files_support      | ON    |
| mysqlx_port              | 33060 |
| mysqlx_port_open_timeout | 0     |
| port                     | 3306  |
| report_host              |       |
| report_password          |       |
| report_port              | 3306  |
| report_user              |       |
| require_secure_transport | OFF   |
+--------------------------+-------+
10 rows in set (0.02 sec)

　　注意：admin_port该参数不需要明确指定，你的mysql端口是3306的话，这里就显示33062.

# 打开第一个连接

[root@fudao_db_cluster_001 ~]#  mysql -utest_r -h 10.192.30.53 -p'f9p%VSfXxcY3kHLJmKIi'
mysql: [Warning] Using a password on the command line interface can be insecure.
Welcome to the MySQL monitor.  Commands end with ; or g.
Your MySQL connection id is 26
Server version: 8.0.17 MySQL Community Server - GPL

Copyright (c) 2000, 2019, Oracle and/or its affiliates. All rights reserved.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or 'h' for help. Type 'c' to clear the current input statement.

mysql> 

# 打开第二个连接

[root@fudao_db_cluster_001 local]# mysql -utest_r -h 10.192.30.53 -p'f9p%VSfXxcY3kHLJmKIi'
mysql: [Warning] Using a password on the command line interface can be insecure.
Welcome to the MySQL monitor.  Commands end with ; or g.
Your MySQL connection id is 27
Server version: 8.0.17 MySQL Community Server - GPL

Copyright (c) 2000, 2019, Oracle and/or its affiliates. All rights reserved.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or 'h' for help. Type 'c' to clear the current input statement.

mysql> 

# 打开第三个连接

[root@fudao_db_cluster_001 local]#  mysql -utest_r -h 10.192.30.53 -p'f9p%VSfXxcY3kHLJmKIi'
mysql: [Warning] Using a password on the command line interface can be insecure.
ERROR 1040 (08004): Too many connections
[root@fudao_db_cluster_001 local]# 

# 用管理端口本地登录

[root@fudao_db_cluster_001 local]# mysql -h 127.0.0.1 -uadmin_m -p'rA75MQy*R*y@KO4z%LZe' -P 33062
mysql: [Warning] Using a password on the command line interface can be insecure.
Welcome to the MySQL monitor.  Commands end with ; or g.
Your MySQL connection id is 29
Server version: 8.0.17 MySQL Community Server - GPL

Copyright (c) 2000, 2019, Oracle and/or its affiliates. All rights reserved.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or 'h' for help. Type 'c' to clear the current input statement.

mysql> 

　　从上面可以看出，当普通用户连接数满后，只能用超级用户本地127.0.0.1或者localhost登录。

[root@fudao_db_cluster_001 local]# mysql -h 10.192.30.53 -uadmin_m -p'rA75MQy*R*y@KO4z%LZe' -P 33062
mysql: [Warning] Using a password on the command line interface can be insecure.
ERROR 2003 (HY000): Can't connect to MySQL server on '10.192.30.53' (111)
[root@fudao_db_cluster_001 local]#