如何限制MySQL根账号的登录失败次数

  ```

  plugin-load-add = validate_password.so

  validate_password_policy = policy_name

  validate_password_length = min_length

  validate_password_number_count = min_number_count

  validate_password_special_char_count = min_special_char_count

  ```

  其中，policy_name是密码策略的名称，可选的值包括LOW、MEDIUM、STRONG，默认为MEDIUM。min_length是密码的最小长度，min_number_count是密码中数字的最小数量，min_special_char_count是密码中特殊字符的最小数量。

  ```

  CREATE TABLE mysql.login_attempts (

      user_host VARCHAR(60) NOT NULL PRIMARY KEY,

      attempts INT NOT NULL DEFAULT 0,

      last_attempt TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP

  ) ENGINE=InnoDB;

  ```

  ```

  DELIMITER //

  CREATE TRIGGER login_failed_trigger BEFORE INSERT ON mysql.user FOR EACH ROW

  BEGIN

      IF NEW.authentication_string = '' THEN

          INSERT INTO mysql.login_attempts (user_host, attempts) VALUES (CONCAT(NEW.user, '@', NEW.host), 1)

          ON DUPLICATE KEY UPDATE attempts = attempts + 1, last_attempt = CURRENT_TIMESTAMP;

      END IF;

  END //

  DELIMITER ;

  ```

  ```

  plugin-load-add = auth_socket.so

  ```

  这将启用auth_socket插件，以便在登录失败时触发触发器。