Java example source code file (ResetPeakThreadCount.java)

This example Java source code file (ResetPeakThreadCount.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

barrier, current, daemon_threads_1, daemon_threads_2, daemon_threads_3, expected, expected_peak_delta_2, interruptedexception, management, mythread, peak, runtimeexception, terminate_1, terminate_2, terminate_3

The ResetPeakThreadCount.java Java example source code

/*
 * Copyright (c) 2003, 2013, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */

/*
 * @test
 * @bug     4892507 8020875 8021335
 * @summary Basic Test for the following reset methods:
 *          - ThreadMXBean.resetPeakThreadCount()
 * @author  Mandy Chung
 * @author  Jaroslav Bachorik
 *
 * @build ResetPeakThreadCount
 * @build ThreadDump
 * @run main/othervm ResetPeakThreadCount
 */

import java.lang.management.*;

public class ResetPeakThreadCount {
    // initial number of new threads started
    private static final int DAEMON_THREADS_1 = 8;
    private static final int EXPECTED_PEAK_DELTA_1 = 8;

    // Terminate half of the threads started
    private static final int TERMINATE_1 = 4;

    // start new threads but expected the peak unchanged
    private static final int DAEMON_THREADS_2 = 2;
    private static final int EXPECTED_PEAK_DELTA_2 = 0;

    // peak thread count reset before starting new threads
    private static final int DAEMON_THREADS_3 = 4;
    private static final int EXPECTED_PEAK_DELTA_3 = 4;

    private static final int TERMINATE_2 = 8;

    private static final int TERMINATE_3 = 2;

    private static final int ALL_THREADS = DAEMON_THREADS_1 +
        DAEMON_THREADS_2 + DAEMON_THREADS_3;
    // barrier for threads communication
    private static final Barrier barrier = new Barrier(DAEMON_THREADS_1);

    private static final Thread allThreads[] = new Thread[ALL_THREADS];
    private static final boolean live[] = new boolean[ALL_THREADS];
    private static final ThreadMXBean mbean = ManagementFactory.getThreadMXBean();
    private static volatile boolean testFailed = false;

    public static void main(String[] argv) throws Exception {
        // This test does not expect any threads to be created
        // by the test harness after main() is invoked.
        // The checkThreadCount() method is to produce more
        // diagnostic information in case any unexpected test failure occur.
        long previous = mbean.getThreadCount();
        long current = previous;

        // reset the peak to start from a scratch
        resetPeak(current);

        // start DAEMON_THREADS_1 number of threads
        current = startThreads(0, DAEMON_THREADS_1, EXPECTED_PEAK_DELTA_1);

        checkThreadCount(previous, current, DAEMON_THREADS_1);
        previous = current;

        // terminate TERMINATE_1 number of threads and reset peak
        current = terminateThreads(0, TERMINATE_1);

        checkThreadCount(previous, current, TERMINATE_1 * -1);

        previous = current;

        // start DAEMON_THREADS_2 number of threads
        // expected peak is unchanged
        current = startThreads(DAEMON_THREADS_1, DAEMON_THREADS_2,
                               EXPECTED_PEAK_DELTA_2);

        checkThreadCount(previous, current, DAEMON_THREADS_2);
        previous = current;

        // Reset the peak
        resetPeak(current);

        // start DAEMON_THREADS_3 number of threads
        current = startThreads(DAEMON_THREADS_1 + DAEMON_THREADS_2,
                               DAEMON_THREADS_3, EXPECTED_PEAK_DELTA_3);

        checkThreadCount(previous, current, DAEMON_THREADS_3);
        previous = current;

        // terminate TERMINATE_2 number of threads and reset peak
        current = terminateThreads(TERMINATE_1, TERMINATE_2);

        checkThreadCount(previous, current, TERMINATE_2 * -1);
        previous = current;

        resetPeak(current);

        // terminate TERMINATE_3 number of threads and reset peak
        current = terminateThreads(TERMINATE_1 + TERMINATE_2, TERMINATE_3);

        checkThreadCount(previous, current, TERMINATE_3 * -1);
        resetPeak(current);

        if (testFailed)
            throw new RuntimeException("TEST FAILED.");

        System.out.println("Test passed");
    }

    private static long startThreads(int from, int count, int delta) throws InterruptedException {
        // get current peak thread count
        long peak1 = mbean.getPeakThreadCount();
        long current = mbean.getThreadCount();

        // Start threads and wait to be sure they all are alive
        System.out.println("Starting " + count + " threads....");
        barrier.set(count);
        synchronized(live) {
            for (int i = from; i < (from + count); i++) {
                live[i] = true;
                allThreads[i] = new MyThread(i);
                allThreads[i].setDaemon(true);
                allThreads[i].start();
            }
        }
        // wait until all threads have started.
        barrier.await();

        // get peak thread count after daemon threads have started
        long peak2 = mbean.getPeakThreadCount();

        System.out.println("   Current = " + mbean.getThreadCount() +
            " Peak before = " + peak1 + " after: " + peak2);

        if (peak2 != (peak1 + delta)) {
            throw new RuntimeException("Current Peak = " + peak2 +
                " Expected to be == previous peak = " + peak1 + " + " +
                delta);
        }
        // wait until the current thread count gets incremented
        while (mbean.getThreadCount() < (current + count)) {
            Thread.sleep(100);
        }
        current = mbean.getThreadCount();
        System.out.println("   Live thread count before returns " + current);
        return current;
    }

    private static long terminateThreads(int from, int count) throws InterruptedException {
        // get current peak thread count
        long peak1 = mbean.getPeakThreadCount();

        // Stop daemon threads and wait to be sure they all are dead
        System.out.println("Terminating " + count + " threads....");
        barrier.set(count);
        synchronized(live) {
            for (int i = from; i < (from+count); i++) {
                live[i] = false;
            }
            live.notifyAll();
        }
        // wait until daemon threads terminated.
        barrier.await();

        // get peak thread count after daemon threads have terminated
        long peak2 = mbean.getPeakThreadCount();
        // assuming no system thread is added
        if (peak2 != peak1) {
            throw new RuntimeException("Current Peak = " + peak2 +
                " Expected to be = previous peak = " + peak1);
        }

        for (int i = from; i < (from+count); i++) {
            allThreads[i].join();
        }

        // there is a race in the counter update logic somewhere causing
        // the thread counters go ff
        // we need to give the terminated threads some extra time to really die
        // JDK-8021335
        Thread.sleep(500);

        long current = mbean.getThreadCount();
        System.out.println("   Live thread count before returns " + current);
        return current;
    }

    private static void resetPeak(long expectedCount) {
        long peak3 = mbean.getPeakThreadCount();
        long current = mbean.getThreadCount();

        // Nightly testing showed some intermittent failure.
        // Check here to get diagnostic information if some strange
        // behavior occurs.
        checkThreadCount(expectedCount, current, 0);

        // Reset peak thread count
        mbean.resetPeakThreadCount();

        long afterResetPeak = mbean.getPeakThreadCount();
        long afterResetCurrent = mbean.getThreadCount();
        System.out.println("Reset peak before = " + peak3 +
            " current = " + current +
            " after reset peak = " + afterResetPeak +
            " current = " + afterResetCurrent);

        if (afterResetPeak != current) {
            throw new RuntimeException("Current Peak after reset = " +
                afterResetPeak +
                " Expected to be = current count = " + current);
        }
    }

    private static void checkThreadCount(long previous, long current, int expectedDelta) {
        if (current != previous + expectedDelta) {
            ThreadDump.threadDump();
            throw new RuntimeException("***** Unexpected thread count:" +
                               " previous = " + previous +
                               " current = " + current +
                               " delta = " + expectedDelta + "*****");
        }
    }

    // The MyThread thread lives as long as correspondent live[i] value is true
    private static class MyThread extends Thread {
        int id;

        MyThread(int id) {
            this.id = id;
        }

        public void run() {
            // signal started
            barrier.signal();
            synchronized(live) {
                while (live[id]) {
                    try {
                        live.wait(100);
                    } catch (InterruptedException e) {
                        System.out.println("Unexpected exception is thrown.");
                        e.printStackTrace(System.out);
                        testFailed = true;
                    }
                }
            }
            // signal about to exit
            barrier.signal();
        }
    }

}