Thread dump programmatically /JDI (Java Debugger I

Question

I like to generate a thread dump programmatically. I've learned that there a basically two ways to do it:

1. Use the "Java Virtual Machine Tool Interface" JVM-TI
2. Use the higher abstracted "Java Debugger Interface" JDI

For the JVM-TI I was able to find some useful information, but I would have to write a JNI-DLL which, at least for the moment, I would like to avoid. With the JDI I can use Java and it seems I'm able to use it from within the application. But I wasn't able to find some kind of tutorial or HOWTO for it. The only documentation I could find, were the Java-Docs http://java.sun.com/j2se/1.5.0/docs/guide/jpda/jdi/ which isn't very helpful, because it doesn't show me how to use this classes.

So, does anybody know of a good tutorial/book I could read?

Thx for any help!

Answer 1

There is a third way: Thread.getAllStackTraces()

http://java.sun.com/javase/6/docs/api/java/lang/Thread.html#getAllStackTraces()

This is much easier than the debugger interface...

Answer 2

Did you consider the remote alternative ? I.e. VisualVM

thead dump with visualVM http://java.sun.com/javase/6/docs/technotes/guides/visualvm/images/applications-window-menu.png

jps and jstack are also useful tools included in JDK 5, providing a quick command line method for obtaining stack traces of all current threads.

This article suggest JDI is also used as a remote tool.

So I am not sure you can triggers a thread dump within your own program, instead you find a way to send to yourself a SIGQUIT signal (kill -3) on Unix platforms, or press the Ctrl-\ key on Unix or Ctrl-Break on Windows platforms.

Plus, JDI wasn't intended to be used to debug the same process in which the JDI client is running. Still this thread I just linked to is the closest I have found to actually use JDI within the same program.

Answer 3

Thread.getAllStackTraces() dumps only the execution trace of all the threads, but doesn't give the information of object locks that have been obtained by a particular thread or the lock on which a particular thread has been waiting. Basically, we'll not be able to nail down deadlocks with this.

Answer 4

You can get just about all the Thread info you need including deadlocks from http://java.sun.com/javase/6/docs/api/java/lang/management/ThreadMXBean.html