JAVA企业级应用Tomcat实战

tomcat简介+安装+调优  以下的url写的很详细

http://blog.oldboyedu.com/java-tomcat/

tomcat检查排错工具

查看fgc次数

#jstat -gcutil pid 1000
[root@iZ2zehet7zctyv30e767syZ conf]# jstat -gcutil 29748 1000
  S0     S1     E      O      P     YGC     YGCT    FGC    FGCT     GCT   
 12.55   0.00  22.01  21.06   3.18     18    2.036    62  250.969  253.006
 12.55   0.00  22.01  21.06   3.18     18    2.036    62  250.969  253.006
 12.55   0.00  22.01  21.06   3.18     18    2.036    62  250.969  253.006
FGC: FGC的次数 这个值很大的话 会导致cpu负载升高 需要查看是否有内存泄漏
FGCT: FGC的时间

查看年轻带，老年代，持久带的内存分配和使用情况

#jmap -heap pid
[root@iZ2zehet7zctyv30e767syZ conf]# jmap -heap 29748
Attaching to process ID 29748, please wait...
Debugger attached successfully.
Server compiler detected.
JVM version is 24.75-b04

using thread-local object allocation.
Parallel GC with 8 thread(s)

Heap Configuration:
   MinHeapFreeRatio = 0
   MaxHeapFreeRatio = 100
   MaxHeapSize      = 2147483648 (2048.0MB)
   NewSize          = 1310720 (1.25MB)
   MaxNewSize       = 17592186044415 MB
   OldSize          = 5439488 (5.1875MB)
   NewRatio         = 2
   SurvivorRatio    = 8
   PermSize         = 1073741824 (1024.0MB)
   MaxPermSize      = 1073741824 (1024.0MB)
   G1HeapRegionSize = 0 (0.0MB)

Heap Usage:
PS Young Generation
Eden Space: #新生代
   capacity = 239075328 (228.0MB)
   used     = 57453560 (54.79198455810547MB)
   free     = 181621768 (173.20801544189453MB)
   24.03157217460766% used
From Space:
   capacity = 238551040 (227.5MB)
   used     = 29933776 (28.547073364257812MB)
   free     = 208617264 (198.9529266357422MB)
   12.548164116157281% used
To Space:
   capacity = 238551040 (227.5MB)
   used     = 0 (0.0MB)
   free     = 238551040 (227.5MB)
   0.0% used
PS Old Generation #年老带
   capacity = 901775360 (860.0MB)
   used     = 189952728 (181.15303802490234MB)
   free     = 711822632 (678.8469619750977MB)
   21.06430674708167% used
PS Perm Generation #持久带
   capacity = 1073741824 (1024.0MB)
   used     = 34181336 (32.597862243652344MB)
   free     = 1039560488 (991.4021377563477MB)
   3.183384984731674% used

介绍三个代的博客

http://blog.163.com/bobile45@126/blog/static/960619922015104113740469/

tomcat其他拍错检查工具

http://blog.csdn.net/u013516966/article/details/76283793

使用Eclipse Memory Analyzer分析Tomcat内存溢出

eclipse下载地址：

https://www.eclipse.org/downloads/   

点击 downLoad 64bit即可

 

1.配置tomcat，当出现内存溢出时生成dump快照

catalina.sh  增加如下配置 
JAVA_OPTS='-XX:HeapDumpPath=/home/qiqi/memerylog'

2. 安装eclipse 并安装插件Memory Analyzer

安装eclipse的时候需要先安装jdk,并配置好环境变量

安装插件方法如下：

Help-Eclipse Marketplace- 在find的位置输入“Memory Analyzer”-然后搜素 会出现这个插件-点击install 安装即可-提示restart now 重启软件 重启即可

打开dump快照的方法：

file-open file - 选择dump快照（java_pid29748.hprof）-打开

**快照通常会比较大，耗费内存和cpu，如果eclipse打不开 就进入其安装目录 修改 eclipse里的内存配置  eplipse.ini文件

 打开后如下图所示  是一个饼图

点击占用内存较大位置的饼图，查看对应的类，截图给开发，运维的工作完成。

 cpu负载过高，就重启tomcat的脚本

有时候一时半刻解决不了，只能当cpu负载过高的时候重启一下tomcat 脚本内容如下：

#!/bin/bash
#created by qiqi 20170808
#description:when cpu load  too high,restart tomcat
source /etc/profile
nowtime=`date +%Y-%m-%d-%H:%M:%S`
# 查找平均负载
load_num=`/usr/bin/uptime | awk '{print $11}' | awk -F . '{print $1}'`
#echo $load_num
if  [ ${load_num} -ge 4 ]
then
                echo "进行重启操作 time:${nowtime}"
                pid=`ps -ef  | grep tomcat | grep '/data/tomcat/temp' | grep -v grep | awk '{print $2}'`
                echo "the tomcat pid is $pid"

                if [ -n "$pid" ];then
                   sleep 1
                   pid=`ps -ef  | grep tomcat | grep '/data/tomcat/temp' | grep -v grep | awk '{print $2}'`
                   if [ -n "$pid" ]; then
                          sleep 1
                          echo "tomcat进程将被杀死."  
                          kill -9 $pid
                   fi
                   sleep 1

                   echo "tomcat进程已经被杀死，先重新启动tomcat."   
                   /data/tomcat/bin/startup.sh
                else
                        echo "tomcat进程不存在，先重新启动tomcat."  
                        /data/tomcat/bin/startup.sh
                fi
else
        echo "load:${load_num},time:${nowtime}" 
fi

echo "<<=========================================================>>"

添加到计划任务：

#每10分钟检测一次 cpu的负载情况
*/10 * * * * /home/qiqi/restart_tomcat.sh  >> /home/qiqi/log

日志显示如下：

load:0,time:2018-03-14-20:30:01
<<=========================================================>>
load:0,time:2018-03-14-20:40:01
<<=========================================================>>
load:0,time:2018-03-14-20:50:01
<<=========================================================>>
load:0,time:2018-03-14-21:00:01
<<=========================================================>>
load:0,time:2018-03-14-21:10:01
<<=========================================================>>
load:0,time:2018-03-14-21:20:01
<<=========================================================>>
load:0,time:2018-03-14-21:30:01
<<=========================================================>>
进行重启操作 time:2018-03-14-21:40:01
the tomcat pid is 7929
tomcat进程将被杀死.
tomcat进程已经被杀死，先重新启动tomcat.
Tomcat started.
<<=========================================================>>
load:0,time:2018-03-14-21:50:01
<<=========================================================>>
load:0,time:2018-03-14-22:00:01