Get PID(Process ID) of Java runtime
Get the PID of the running java runtime using the operating system. Use ps command in Linux/Mac/Unix and in windows use Task Manager’s process tab.
Another easy option is to use jps tool provided by JDK. jps lists all java Processes of a user.
Thread Dump
A Java thread dump gives vital information about all the threads in a JVM. Information includes execution point of each thread and the locks( if any) on which threads are waiting.
Thread dump using JDK jstack
Oracle JDK provides a utility called jstack which can take a thread dump of a running Java application
usage:
jstack -l <PID> > thread.tdump
Eg., jstack -l 413 > thread.tdump /** 413 is the Java Process ID **/
To take the thread dump in a loop while running load test use the following script:
while true do jstack <PID> >> stack-`date +%s`.txt sleep 60 done
Heap Dump
A heap dump is a snapshot of a JVM’s heap space, complete with all object references. This is a (often very large) binary file and needs special tools to be analyzed.
To obtain a heap dump of an existing JVM process on Sun / Oracle JVMs use the jmap tool.
$ jmap -dump:format=b,file=heapdump.jmap <PID>
