Hi Christoph, You might use ThreadGroup.enumerate(Thread[], recurse) after walking up the parents to the root ThreadGroup. $.02, Roger On 10/27/2017 11:23 AM, Christoph Dreis wrote:
Hey,
I don't know if this is the correct mailing list for this specific topic. Please let me know in case it isn't.
I'm currently trying to improve the live-monitoring of an application and would like to get a simple overview of how many threads are in state RUNNABLE, BLOCKED and so on. For this I need to get all threads in the first place to iterate on. I know of two ways how to do that programmatically:
1) ThreadMXBean.dumpAllThreads() which gives me an array of ThreadInfo objects on which I could call getThreadState() 2) Thread.getAllStackTraces().keySet() which gives me a Set of Thread objects on which I could call getState()
Either 1) or 2) both dump the threads, which seems like a lot of overhead for this task and therefore presumably aren't supposed to be executed every X seconds. Using reflection to make the private native Thread.getThreads() available - if that's even possible(?) - doesn't seem correct either. Is there an alternative for this?
If not, I'd like to suggest the addition of two in my opinion more lightweight alternative APIs in Thread and/or ThreadMXBean (ThreadImpl). Here is what I'm thinking of in a rough and untested state:
public static Map<Thread.State, Integer> getAllThreadStateCounts() { // Get a snapshot of the list of all threads Thread[] threads = getThreads(); Map<Thread.State, Integer> m = new EnumMap<>(Thread.State.class); for (int i = 0; i < threads.length; i++) { m.merge(threads[i].getState(), 1, Integer::sum); } return m; }
public static int getThreadCountByState(Thread.State state) { // Get a snapshot of the list of all threads Thread[] threads = getThreads(); int counter = 0; for (int i = 0; i < threads.length; i++) { if (state == threads[i].getState()) { counter++; } } return counter; }
Is this something that could be worthwhile? Let me know what you think.
Cheers, Christoph