Mysql8出来有一段时间了，有很多新特性非常吸引人，于是就安装好mysql-8.0.21数据库尝尝鲜。数据库是用二级制方式安装的，安装过程不复杂，如果想了解二进制安装详细过程，可以在文章下方留言，我会更新一篇文章，详细介绍安装过程和mysql8的参数。

mysql-8.0.21数据库安装好之后，就试着用sysbench建张10W记录的表，测试一下降序索引特性。

首先在数据库中创建了用于压测的数据库和用户

create database sbtest;CREATE USER 'tony'@'%' IDENTIFIED BY 'tony';GRANT ALL ON *.* TO 'tony'@'%';flush privileges;

数据库和用户都创建好之后，就用sysbench插入测试数据

sysbench /usr/share/sysbench/tests/include/oltp_legacy/oltp.lua --mysql-socket=/data/mysql/mysql8/run/3308/mysql.sock --mysql-user=tony --mysql-password='tony'  --mysql-db=sbtest --oltp-test-mode=complex --oltp-tables-count=1 --oltp-table-size=100000 --threads=128  --oltp-nontrx-mode=select --oltp-read-only=off --max-time=120 --report-interval=5 prepareFATAL: unable to connect to MySQL server on socket '/data/mysql/mysql8/run/3308/mysql.sock', aborting...FATAL: error 2059: Authentication plugin 'caching_sha2_password' cannot be loaded: /usr/lib64/mysql/plugin/caching_sha2_password.so: cannot open shared object file: No such file or directoryFATAL: `prepare' function failed: /usr/share/sysbench/tests/include/oltp_legacy/common.lua:111: Failed to connect to the database

可是报错了，FATAL: error 2059: Authentication plugin 'caching_sha2_password' cannot be loaded:，认证组件“caching_sha2_password”没有被加载，查了一下资料，原来在mysql8以后，用户连接默认认证组件改为“caching_sha2_password”，而mysql5.7以前，默认的用户认证组件为“mysql_native_password”。

既然知道了原因，就临时将tony用户的认证组件修改“mysql_native_password”，然后运行sysbench插入数据

ALTER USER tony IDENTIFIED WITH mysql_native_password;flush privileges;[mysql@mysql ~]$ sysbench /usr/share/sysbench/tests/include/oltp_legacy/oltp.lua --mysql-socket=/data/mysql/mysql8/run/3308/mysql.sock --mysql-user=tony --mysql-password='tony'  --mysql-db=sbtest --oltp-test-mode=complex --oltp-tables-count=1 --oltp-table-size=100000 --threads=128  --oltp-nontrx-mode=select --oltp-read-only=off --max-time=120 --report-interval=5 prepareWARNING: --max-time is deprecated, use --time insteadsysbench 1.0.20 (using bundled LuaJIT 2.1.0-beta2)FATAL: unable to connect to MySQL server on socket '/data/mysql/mysql8/run/3308/mysql.sock', aborting...FATAL: error 1045: Access denied for user 'tony'@'localhost' (using password: YES)FATAL: `prepare' function failed: /usr/share/sysbench/tests/include/oltp_legacy/common.lua:111: Failed to connect to the database

竟然还报错，这次是连接不上库，为什么呢，检查用户是否正常

[root@localhost] 16:54:13 [performance_schema]>select user,host,plugin from mysql.user where user='tony';+------+------+-----------------------+| user | host | plugin                |+------+------+-----------------------+| tony | %    | mysql_native_password |+------+------+-----------------------+1 row in set (0.00 sec)

tony用户的host是不限制IP段了，plugin也修改成mysql_native_password，难道是密码不对

[root@localhost] 16:56:08 [performance_schema]>select user,host,plugin,authentication_string from mysql.user where user='tony';+------+------+-----------------------+-----------------------+| user | host | plugin                | authentication_string |+------+------+-----------------------+-----------------------+| tony | %    | mysql_native_password |                       |+------+------+-----------------------+-----------------------+1 row in set (0.71 sec)

看到这里，有没有想说点什么，密码竟然变成空了，原来执行修改认证组件命令时，也将密码置空了。

ALTER USER tony IDENTIFIED WITH mysql_native_password;

问题原因找到了，大家在生产操作时一定要注意，正确修改认证组件命令如下所示

alter user 'tony'@'%' identified with mysql_native_password by 'tony';flush privileges;

搞不好，就会出现大片应用连接不上数据库的尴尬事情了。