查询数据库当前设置的最大连接数
mysql> show status like 'Threads%'; +-------------------+-------+ | Variable_name | Value | +-------------------+-------+ | Threads_cached | 58 | | Threads_connected | 57 | ###这个数值指的是打开的连接数 | Threads_created | 3676 | | Threads_running | 4 | ###这个数值指的是激活的连接数，这个数值一般远低于connected数值 +-------------------+-------+
Threads_connected 跟show processlist结果相同，表示当前连接数。准确的来说，Threads_running是代表当前并发数
这是是查询数据库当前设置的最大连接数
mysql> show variables like '%max_connections%'; +-----------------+-------+ | Variable_name | Value | +-----------------+-------+ | max_connections | 1000 | +-----------------+-------+
可以在/etc/my.cnf里面设置数据库的最大连接数
[mysqld] max_connections = 1000
查看mysql连接数：
show full processlist;
查看sleep退出时间限制：
show variables like “%timeout%”; +-----------------------------+----------+ | Variable_name | Value | +-----------------------------+----------+ | connect_timeout | 10 | | delayed_insert_timeout | 300 | | innodb_flush_log_at_timeout | 1 | | innodb_lock_wait_timeout | 50 | | innodb_rollback_on_timeout | OFF | | interactive_timeout | 28800 | | lock_wait_timeout | 31536000 | | net_read_timeout | 30 | | net_write_timeout | 60 | | slave_net_timeout | 3600 | | wait_timeout | 28800 | +-----------------------------+----------+ 11 rows in set (0.00 sec)
临时生效命令(注意全局 变量和session变量的区别，下面是全局变量的修改)：
set global interactive_timeout=60; flush PRIVILEGES; set global wait_timeout=60; flush PRIVILEGES; show global variables like '%timeout%';
永久生效命令：
编辑 /etc/my.cnf,在mysqld 下 新增 timeout参数，设置为120秒，如下：
【mysqld】 wait_timeout=120 interactive_timeout=120
注意：要同时设置interactive_timeout和wait_timeout才会生效。
编写脚本杀死sleep进程：
#!/bin/sh
user=root
passwd=mysql密码
host=localhost
while :
do
n=`mysqladmin processlist -u$user -p$passwd -h$host | grep -i sleep | grep '10.10.11' | wc -l`
date=`date +%Y%m%d[%H:%M:%S]`
echo $n >> /tmp/sleep.log
if [ "$n" -gt 20 ]
then
for i in `mysqladmin processlist -uroot -p5432b400aa9c9fb0c92b543dce97c244 -hlocalhost | grep -i sleep | grep '10.10.11' | awk '{print $2}'`
do
mysqladmin -u$user -p$passwd -h$host kill $i
done
echo "sleep is too many I killed it " >> /tmp/sleep.log
echo "$date : $n" >> /tmp/sleep.log
fi
sleep 1
done