MySQL 5.5一般可以通过修改改参数来（基线默认是1），debug mysql.err中记录warning，note信息，如果应用端连接数据库由于用户密码异常可以在my.err中记录用户连接失败的提示信息，且多次连接失败会出现连接失败报警。
mysql> show variables like 'log_warnings%';
+---------------+-------+
| Variable_name | Value |
+---------------+-------+
| log_warnings | 1 |
+---------------+-------+

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修改方式：
set global log_warnings=2;
MySQL 5.5版本官方文档中，并没有用户锁的状态。因此不存在用户会被锁。。

The account-locking capability depends on the presence of the account_locked column in the
mysql.user table. For upgrades to MySQL 5.7.6 and later from older versions, run mysql_upgrade
to ensure that this column exists. For nonupgraded installations that have no account_locked
column, the server treats all accounts as unlocked, and using the ACCOUNT LOCK or ACCOUNT
UNLOCK clauses produces an error.

MySQL 5.5的用户信息中没有用户锁的字段
4. row
Host: ::1
User: root
Password: *13C230E7E4DDA7CCF4BED86963D2B066390F3E56
Select_priv: Y
Insert_priv: Y
Update_priv: Y
Delete_priv: Y
Create_priv: Y
Drop_priv: Y
Reload_priv: Y
Shutdown_priv: Y
Process_priv: Y
File_priv: Y
Grant_priv: Y
References_priv: Y
Index_priv: Y
Alter_priv: Y
Show_db_priv: Y
Super_priv: Y
Create_tmp_table_priv: Y
Lock_tables_priv: Y
Execute_priv: Y
Repl_slave_priv: Y
Repl_client_priv: Y
Create_view_priv: Y
Show_view_priv: Y
Create_routine_priv: Y
Alter_routine_priv: Y
Create_user_priv: Y
Event_priv: Y
Trigger_priv: Y
Create_tablespace_priv: Y
ssl_type:
ssl_cipher:
x509_issuer:
x509_subject:
max_questions: 0
max_updates: 0
max_connections: 0
max_user_connections: 0
plugin:
authentication_string:
4 rows in set (0.00 sec)

MySQL 5.7的用户信息中account_locked
2. row
Host: %
User: root
Select_priv: Y
Insert_priv: Y
Update_priv: Y
Delete_priv: Y
Create_priv: Y
Drop_priv: Y
Reload_priv: Y
Shutdown_priv: Y
Process_priv: Y
File_priv: Y
Grant_priv: N
References_priv: Y
Index_priv: Y
Alter_priv: Y
Show_db_priv: Y
Super_priv: Y
Create_tmp_table_priv: Y
Lock_tables_priv: Y
Execute_priv: Y
Repl_slave_priv: Y
Repl_client_priv: Y
Create_view_priv: Y
Show_view_priv: Y
Create_routine_priv: Y
Alter_routine_priv: Y
Create_user_priv: Y
Event_priv: Y
Trigger_priv: Y
Create_tablespace_priv: Y
ssl_type:
ssl_cipher:
x509_issuer:
x509_subject:
max_questions: 0
max_updates: 0
max_connections: 0
max_user_connections: 0
plugin: mysql_native_password
authentication_string: *D61994AAB9327E97C4BECC73E497951CFC723C99
password_expired: N
password_last_changed: 2018-04-14 22:20:00
password_lifetime: NULL
account_locked: N
2 rows in set (0.00 sec)

可以通过如下方式查看用户锁状态、但都仅限MySQL 5.7.6以上
mysql> show create user 'root';
+-------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| CREATE USER for root@% |
+-------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| CREATE USER 'root'@'%' IDENTIFIED WITH 'mysql_native_password' AS '*D61994AAB9327E97C4BECC73E497951CFC723C99' REQUIRE NONE PASSWORD EXPIRE DEFAULT ACCOUNT UNLOCK |

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