Linux定时检测内存，若使用率超过指标，重启Tomcat并清空内存

#!/bin/bash  

echo "start SyncCleanCache.sh..." >> /var/log/mem_detect.log

#系统分配的区总量

mem_total=`free -m | awk 'NR==2' | awk '{print $2}'`   

#当前剩余的大小

mem_free=`free -m | awk 'NR==3' | awk '{print $4}'`  

#当前已使用的used大小

mem_used=`free -m | grep Mem | awk '{print  $3}'`   

echo "已使用:" >> /var/log/mem_detect.log

echo $mem_used >> /var/log/mem_detect.log

if (($mem_used != )); then   

#如果已被使用，则计算当前剩余free所占总量的百分比，用小数来表示，要在小数点前面补一个整数位0

mem_per=`echo "scale=2;$mem_free/$mem_total" | bc`

DATA="$(date -d "today" +"%Y-%m-%d-%H-%M") free percent is : $mem_per"

echo $DATA >> /var/log/mem_detect.log

#设置的告警值为20%(即使用超过80%的时候告警)。

mem_warn=0.20   

#当前剩余百分比与告警值进行比较（当大于告警值(即剩余20%以上)时会返回1，小于(即剩余不足20%)时会返回0 ）

mem_now=`expr $mem_per \> $mem_warn`   

echo "是否大于告警值:" >> /var/log/mem_detect.log

echo $mem_now >> /var/log/mem_detect.log

#如果当前使用超过80%（即剩余小于20%，上面的返回值等于0），释放内存

if (($mem_now == )); then  

echo "more than percent 80..." >> /var/log/mem_detect.log

#重启tomcat并清空缓存

pid=`ps aux | grep tomcat | grep -v grep | grep -v retomcat | awk '{print $2}'`

echo $pid

if [ -n "$pid" ]

then

{

   echo ===========shutdown================

   /usr/local/apache-tomcat-7.0./bin/shutdown.sh

   sleep

   pid=`ps aux | grep tomcat | grep -v grep | grep -v retomcat | awk '{print $2}'`

   sync

   echo  > /proc/sys/vm/drop_caches

   echo  > /proc/sys/vm/drop_caches

   echo  > /proc/sys/vm/drop_caches

   if [ -n "$pid" ]

   then

    {

      sleep

      echo ========kill tomcat==============

      kill - $pid

      sync

      echo  > /proc/sys/vm/drop_caches

      echo  > /proc/sys/vm/drop_caches

      echo  > /proc/sys/vm/drop_caches

    }

   fi

   sleep

   echo ===========startup.sh==============

   /usr/local/apache-tomcat-7.0./bin/startup.sh

 }

else

echo ===========startup.sh==============

/usr/local/apache-tomcat-7.0./bin/startup.sh  

fi 

sync

echo  > /proc/sys/vm/drop_caches

echo  > /proc/sys/vm/drop_caches

echo  > /proc/sys/vm/drop_caches

#将release memory OK !写入temp文件夹的memstat_日期.log日志中

echo "--->release memory OK ! " >> /var/log/mem_detect.log

fi

fi