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mysql 参数max_connect_errors研究

news 来源：原创 2025/5/8 3:02:16

1.在server端设置max_connect_errors=3，超过3次连接错误就block
mysql> set global max_connect_errors=3;
Query OK, 0 rows affected (0.00 sec)

2.在客户端10.153.56.25连接server,不输入密码四次，第五次依旧连接上了
[mysql@t3-tksbscms-tkcms-db-mysql01-ma01 bin]$ mysql -h 10.153.35.2 -u root -p
Enter password:
ERROR 1045 (28000): Access denied for user 'root'@'10.153.56.25' (using password: NO)
[mysql@t3-tksbscms-tkcms-db-mysql01-ma01 bin]$ mysql -h 10.153.35.2 -u root -p
Enter password:
ERROR 1045 (28000): Access denied for user 'root'@'10.153.56.25' (using password: NO)
[mysql@t3-tksbscms-tkcms-db-mysql01-ma01 bin]$ mysql -h 10.153.35.2 -u root -p
Enter password:
ERROR 1045 (28000): Access denied for user 'root'@'10.153.56.25' (using password: NO)
[mysql@t3-tksbscms-tkcms-db-mysql01-ma01 bin]$ mysql -h 10.153.35.2 -u root -p
Enter password:
ERROR 1045 (28000): Access denied for user 'root'@'10.153.56.25' (using password: NO)
[mysql@t3-tksbscms-tkcms-db-mysql01-ma01 bin]$ mysql -h 10.153.35.2 -u root -p
Enter password:
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 17
Server version: 5.7.26-log MySQL Community Server (GPL)

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>

3.在server端看到10.153.56.25
HOST_VALIDATED: YES ，
SUM_CONNECT_ERRORS: 0 ，
COUNT_HOST_BLOCKED_ERRORS: 0
COUNT_AUTHENTICATION_ERRORS: 4
说明密码错误并不数据连接错误
mysql> select * from performance_schema.host_cache\G
*************************** 1. row ***************************
IP: 10.153.56.25
HOST: NULL
HOST_VALIDATED: YES
SUM_CONNECT_ERRORS: 0
COUNT_HOST_BLOCKED_ERRORS: 0
COUNT_NAMEINFO_TRANSIENT_ERRORS: 0
COUNT_NAMEINFO_PERMANENT_ERRORS: 1
COUNT_FORMAT_ERRORS: 0
COUNT_ADDRINFO_TRANSIENT_ERRORS: 0
COUNT_ADDRINFO_PERMANENT_ERRORS: 0
COUNT_FCRDNS_ERRORS: 0
COUNT_HOST_ACL_ERRORS: 0
COUNT_NO_AUTH_PLUGIN_ERRORS: 0
COUNT_AUTH_PLUGIN_ERRORS: 0
COUNT_HANDSHAKE_ERRORS: 0
COUNT_PROXY_USER_ERRORS: 0
COUNT_PROXY_USER_ACL_ERRORS: 0
COUNT_AUTHENTICATION_ERRORS: 4
COUNT_SSL_ERRORS: 0
COUNT_MAX_USER_CONNECTIONS_ERRORS: 0
COUNT_MAX_USER_CONNECTIONS_PER_HOUR_ERRORS: 0
COUNT_DEFAULT_DATABASE_ERRORS: 0
COUNT_INIT_CONNECT_ERRORS: 0
COUNT_LOCAL_ERRORS: 0
COUNT_UNKNOWN_ERRORS: 0
FIRST_SEEN: 2025-02-13 14:26:57
LAST_SEEN: 2025-02-13 14:27:10
FIRST_ERROR_SEEN: 2025-02-13 14:26:57
LAST_ERROR_SEEN: 2025-02-13 14:27:02
1 row in set (0.00 sec)

4.通过telnet 10.153.35.2 3306命令，超过3次后第四次后就报错：
Host '10.153.56.25' is blocked because of many connection errors;
正常的mysql -h 10.153.35.2 -u root -p输入密码也被 block了

[mysql@t3-tksbscms-tkcms-db-mysql01-ma01 bin]$ telnet 10.153.35.2 3306
Trying 10.153.35.2...
Connected to 10.153.35.2.
Escape character is '^]'.
N
5.7.26-logM:Nu
-A%a-9c2Ubmysql_native_password

!#08S01Got packets out of orderConnection closed by foreign host.
[mysql@t3-tksbscms-tkcms-db-mysql01-ma01 bin]$
[mysql@t3-tksbscms-tkcms-db-mysql01-ma01 bin]$ telnet 10.153.35.2 3306
Trying 10.153.35.2...
Connected to 10.153.35.2.
Escape character is '^]'.
N
5.7.26-logS8IQA-CNOG\+|mSCmysql_native_password

!#08S01Got packets out of orderConnection closed by foreign host.
[mysql@t3-tksbscms-tkcms-db-mysql01-ma01 bin]$ telnet 10.153.35.2 3306
Trying 10.153.35.2...
Connected to 10.153.35.2.
Escape character is '^]'.
jHost '10.153.56.25' is blocked because of many connection errors; unblock with 'mysqladmin flush-hosts'Connection closed by foreign host.
[mysql@t3-tksbscms-tkcms-db-mysql01-ma01 bin]$ telnet 10.153.35.2 3306
Trying 10.153.35.2...
Connected to 10.153.35.2.
Escape character is '^]'.
jHost '10.153.56.25' is blocked because of many connection errors; unblock with 'mysqladmin flush-hosts'Connection closed by foreign host.
[mysql@t3-tksbscms-tkcms-db-mysql01-ma01 bin]$ mysql -h 10.153.35.2 -u root -p
Enter password:
ERROR 1129 (HY000): Host '10.153.56.25' is blocked because of many connection errors; unblock with 'mysqladmin flush-hosts'

5.server端可以看到
SUM_CONNECT_ERRORS: 3
COUNT_HOST_BLOCKED_ERRORS: 3
mysql> select * from performance_schema.host_cache\G
*************************** 1. row ***************************
IP: 10.153.56.25
HOST: NULL
HOST_VALIDATED: YES
SUM_CONNECT_ERRORS: 3
COUNT_HOST_BLOCKED_ERRORS: 3
COUNT_NAMEINFO_TRANSIENT_ERRORS: 0
COUNT_NAMEINFO_PERMANENT_ERRORS: 1
COUNT_FORMAT_ERRORS: 0
COUNT_ADDRINFO_TRANSIENT_ERRORS: 0
COUNT_ADDRINFO_PERMANENT_ERRORS: 0
COUNT_FCRDNS_ERRORS: 0
COUNT_HOST_ACL_ERRORS: 0
COUNT_NO_AUTH_PLUGIN_ERRORS: 0
COUNT_AUTH_PLUGIN_ERRORS: 0
COUNT_HANDSHAKE_ERRORS: 3
COUNT_PROXY_USER_ERRORS: 0
COUNT_PROXY_USER_ACL_ERRORS: 0
COUNT_AUTHENTICATION_ERRORS: 4
COUNT_SSL_ERRORS: 0
COUNT_MAX_USER_CONNECTIONS_ERRORS: 0
COUNT_MAX_USER_CONNECTIONS_PER_HOUR_ERRORS: 0
COUNT_DEFAULT_DATABASE_ERRORS: 0
COUNT_INIT_CONNECT_ERRORS: 0
COUNT_LOCAL_ERRORS: 0
COUNT_UNKNOWN_ERRORS: 0
FIRST_SEEN: 2025-02-13 14:26:57
LAST_SEEN: 2025-02-13 14:33:15
FIRST_ERROR_SEEN: 2025-02-13 14:26:57
LAST_ERROR_SEEN: 2025-02-13 14:33:15
1 row in set (0.00 sec)

6.解决办法就是在server端执行flush hosts;
mysql> flush hosts;
Query OK, 0 rows affected (0.00 sec)

mysql> select * from performance_schema.host_cache\G
Empty set (0.00 sec)

可以看到10.153.56.25这个client又可以连接了
[mysql@t3-tksbscms-tkcms-db-mysql01-ma01 bin]$ mysql -h 10.153.35.2 -u root -p
Enter password:
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 24
Server version: 5.7.26-log MySQL Community Server (GPL)

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>