Heap dump on a Unix machine

After exploring the Jay/Faisal's blog on 'jmap' java utility usage and Heap dump. It is really great work by Jay/Faisal. I just thought that similar kind of experiment we did long back on UNIX machines. I am glad to sharing that with you guys. 

Last year, we were struggling to overcome the OutOfMemoryError, which would effect the most of productive hours. In this assignment I need to figure out what process is causing the low memory in the environment is identified by searching a all log files in the machine. Assume that all the WebLogic instance log files are collected into common directory structure, each of them are stored respective instance named folder.

Script 1:

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1. #==============================================================
2. # Name  : CheckLogs.sh
3. # Created by : Pavan Devarakonda
4. # Script for searching all WebLogic instances logs in the box
5. #==============================================================
6. insts=`ls /path/instances|grep web`
7. phrase=$1
8. date
9. for x in $insts
10. do
11.         echo 'Checking in the :' $x
12.         cd /path/instances/$x/logs
13.         egrep -i $phrase instance*log
14.         egrep -i $phrase instance*out
15. done
16.  
17. # Know the CPU load average at this time
18. date
19. uptime

After identifying the impacted instances, I need to take the heap dump of that particular instance with corresponding process id.

Script 2:

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1. #=======================================================
2. # Name : InstanceHeapdump.sh
3. # This script will takes instance name as input
4. # Takes the thread dump and also takes heap dump
5. #=======================================================
6.  
7. if [ "$1" = "" ]; then
8.         echo "Usage : $0 <instance>"
9.         exit
10. else
11.         instance="$1"
12.         user=$LOGNAME
13.         ppid=`ps -fu $user|grep $instance|grep startMan|grep -v grep|awk '{print $2}'`
14.         wpid=`ps -fu $user|grep $ppid|grep startWebLogic.sh|awk '{print $2}'`
15.         jpid=`ps -fu $user|grep $wpid|grep java|awk '{print $2}'`
16.         echo 'The Java PID:' $jpid
17.         kill -3 $jpid
18.         if [ $jpid = "" ]; then
19.                 echo "Invalid instance input..."
20.                 exit
21.         else
22.                 jmap -heap:format=b $jpid
23.                 mv heap.bin $instance_heap.bin
24.         fi
25. fi

This could give you one more way of finding a java process in UNIX machine. You can use jps command instead of three lines of awk filters. In this same script to make hold the java process not to crash, we can call a WLST script to suspend the instance and then you can happily take the heap dump.

What to do after heapdump creation?
Follow the Faisal tips to find memory leaks, use eclipse MAT that is comfortable for your system.