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 != 0)); 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=0`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 == 0)); 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-7.0.65/bin/shutdown.sh  
   sleep 1   
   pid=`ps aux | grep tomcat | grep -v grep | grep -v retomcat | awk ‘{print $2}‘`

   sync
   echo 1 > /proc/sys/vm/drop_caches
   echo 2 > /proc/sys/vm/drop_caches
   echo 3 > /proc/sys/vm/drop_caches
  
   if [ -n "$pid" ]  
   then  
    {  
      sleep 1   
      echo ========kill tomcat==============    
      kill -9 $pid  
      sync  
      echo 1 > /proc/sys/vm/drop_caches  
      echo 2 > /proc/sys/vm/drop_caches  
      echo 3 > /proc/sys/vm/drop_caches 
    }  
   fi  
   sleep 2  
   echo ===========startup.sh==============  
   /usr/local/apache-tomcat-7.0.65/bin/startup.sh  
 }  
else  
echo ===========startup.sh==============  
/usr/local/apache-tomcat-7.0.65/bin/startup.sh  
  
fi 

sync  
echo 1 > /proc/sys/vm/drop_caches  
echo 2 > /proc/sys/vm/drop_caches  
echo 3 > /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