Host 'host_name' is blocked because of many connection errors

Обращаются клиенты с проблемой:

Host 'host_name' is blocked because of many connection errors.
Unblock with 'mysqladmin flush-hosts'

Смотрим, какое значение max_connect_erros выставлено сейчас:

# mysql -uroot -p -e "SHOW VARIABLES LIKE '%max_connect_errors%';"
+--------------------+-------+
| Variable_name      | Value |
+--------------------+-------+
| max_connect_errors | 10    |
+--------------------+-------+

Как-то маловато, увеличим хотя бы до 100:
# mysql -uroot -p -e "SET GLOBAL max_connect_errors=100;"

Проверяем:
# mysql -uroot -p -e "SHOW VARIABLES LIKE '%max_connect_errors%';"
+--------------------+-------+
| Variable_name      | Value |
+--------------------+-------+
| max_connect_errors | 100   |
+--------------------+-------+

Документация:

http://dev.mysql.com/doc/refman/5.5/en/blocked-host.html

http://dev.mysql.com/doc/refman/5.5/en/server-system-variables.html#sysvar_max_connect_errors