MySQL的show processlist命令可以显示当时的会话情况,但很多时候都需要查看出问题当时的状态,可惜MySQL没有提供类似history session这样的功能。于是为了方便问题排查,自己写了一个非常简单的抓取MySQL现场session的脚本,生产数据库已经用了很长时间,感觉对trouble shooting还是挺有用的。脚本文件get_processlist.sh内容如下:
#!/bin/bash
source /home/mysql/.bashrc
dt=`date '+%y%m%d_%h%m%s'`
mysql -uroot -p123456 -p3306 -h127.0.0.1 -e "
select t1.*
from information_schema.processlist t1,
(select count(1) c from information_schema.processlist where info is not null) t2
where t2.c>=50;" > /home/mysql/processlist.txt
if test -s /home/mysql/processlist.txt; then
mv /home/mysql/processlist.txt /home/mysql/processlist_18251/processlist_${dt}.txt
mysql -uroot -p123456 -p18251 -h127.0.0.1 -e "
select * from information_schema.innodb_trx;
select * from information_schema.innodb_lock_waits;
select * from information_schema.innodb_locks;" > /home/mysql/processlist/innodb_locks_${dt}.txt
else
rm /home/mysql/processlist.txt
fi
find /home/mysql/processlist/* -type f -mtime +10 -exec rm {} \;
说明:
将脚本放到crontab中,每分钟执行一次:
* * * * * /home/mysql/dbbat/get_processlist.sh
严格说获得的是1分钟之内的准现场,这种设计一是实现简单,二是对生产负载无影响。