1、线程池active threads含义
https://stackoverflow.com/questions/63256056/what-does-active-threads-mean-in-threadpoolexecutor
https://community.jiguang.cn/article/464210
https://blog.csdn.net/u010657094/article/details/110477635
2、logback-spring.xml
https://www.jianshu.com/p/6f093b0b0c8a
https://mp.weixin.qq.com/s/ld0a4fy7lnvxTsmYCi7x_A
https://blog.csdn.net/xu_san_duo/article/details/80364600
3、mysql索引原理
https://mp.weixin.qq.com/s/ZDM_ttWCstw0mUwGtUEciw
4、rdb
https://www.cnblogs.com/ysocean/p/9114268.html