Can you suspend a Java app and get a snapshot of it's threads from within the app?

Question

I'm looking at writing monitoring code that runs inside a Java application and periodically takes a snapshot of running threads and displays some call stack information on each.

Ideally this would be extended for profiling and/or monitoring.

I don't want to use an external tool, as this is for self educational purposes.

Answer 1

Have you looked into the methods of the Thread class such as Thread.enumerate(), Thread.activeCount(), Thread.getName() ?

Answer 2

Take a look at ThreadMXBean.dumpAllThreads(boolean, boolean)

ThreadMXBean bean = ManagementFactory.getThreadMXBean();
ThreadInfo[] info = bean.dumpAllThreads(true, true);

Answer 3

Have you tried Thread.getAllStackTraces()

Answer 4

You could register the threads you want to watch at creation time, and have a separate metrics thread to do the monitoring. You would want to build certain metrics into the thread, such as maybe a list of recent running times, current throughput, or other sorts of metrics.

Answer 5

kill -SIGQUIT {java_process}

will dump all stack traces in the stdout of the java process.