Java wait for all threads before terminating

Question

I am trying to test an application with Jmeter. The application uses a proprietary library that creates multiple threads. In JMeter I have created a AbstractJavaSamplerClient, which does not seem to wait for all the other threads that might be generated in the application. Instead it just runs its own default method and closes leaving the other threads running in the background - since I am connecting to a server in the application, I can see through the server logs that it is still connected. Since I don't have the references to the other threads as they are instantiated through the proprietary library, I can't use the common solutions of wait() or join().How can I get the main thread to wait for all the threads (none of which I have references too)?

Answer 1

Put all work with the library in a separate thread in a specially created thread group. The library will create new threads in that thread group and its descendants. List all threads of that group recursively with group.enumerate(new Thread[group.activeCount()*2],true) . Then you can join() them all.

Answer 2

You can start with

Thread.getAllStackTraces().keySet();

which will give you a set of all running threads. This will include those you are interested in and all the other threads, including those internal to the JVM.

Hopefully you'll be able to filter out the ones you are interested in by name, and then you can join() them.