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Java example source code file (MonitorVmStartTerminate.java)

This example Java source code file (MonitorVmStartTerminate.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

countdownlatch, execinterval, integer, interruptedexception, javaprocess, matcher, monitorexception, net, network, regex, sleeperlistener, sleeperstarter, sleeptime, started, string, threading, threads, urisyntaxexception, util, vmidentifier

The MonitorVmStartTerminate.java Java example source code

/*
 * Copyright (c) 2004, 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.
 */

import java.util.concurrent.CountDownLatch;
import java.util.regex.*;
import java.util.*;
import java.net.URISyntaxException;
import java.io.IOException;
import sun.jvmstat.monitor.*;
import sun.jvmstat.monitor.event.*;

public class MonitorVmStartTerminate {

    private static final int SLEEPERS = 10;
    private static final int SLEEPTIME = 5000;     // sleep time for a sleeper
    private static final int EXECINTERVAL = 3000;   // wait time between exec's

    public static void main(String args[]) throws Exception {

        long now = System.currentTimeMillis();

        String sleeperArgs = SLEEPTIME + " " + now;
        String sleeperPattern = "Sleeper " + sleeperArgs + " \\d+$";

        MonitoredHost host = MonitoredHost.getMonitoredHost("localhost");
        host.setInterval(200);

        Matcher matcher = Pattern.compile(sleeperPattern).matcher("");
        SleeperListener listener = new SleeperListener(host, matcher, SLEEPERS);
        host.addHostListener(listener);

        SleeperStarter ss = new SleeperStarter(SLEEPERS, EXECINTERVAL,
                                               sleeperArgs);
        ss.start();

        System.out.println("Waiting for "
                           + SLEEPERS + " sleepers to terminate");
        try {
            ss.join();
        } catch (InterruptedException e) {
            throw new Exception("Timed out waiting for sleepers");
        }
        listener.waitForSleepersToStart();
        listener.waitForSleepersToTerminate();
    }

    public static class SleeperListener implements HostListener {

        private final List<Integer> targets =  new ArrayList<>();
        private final CountDownLatch terminateLatch;
        private final CountDownLatch startLatch;
        private final MonitoredHost host;
        private final Matcher patternMatcher;

        public SleeperListener(MonitoredHost host, Matcher matcher, int count) {
            this.host = host;
            this.patternMatcher = matcher;
            this.terminateLatch = new CountDownLatch(count);
            this.startLatch = new CountDownLatch(count);
        }

        public void waitForSleepersToTerminate() throws InterruptedException {
            terminateLatch.await();
        }

        public void waitForSleepersToStart() throws InterruptedException {
            startLatch.await();
        }

        private void printList(Set<Integer> list, String msg) {
            System.out.println(msg + ":");
            for (Integer lvmid : list) {
                try {
                    VmIdentifier vmid = new VmIdentifier("//" + lvmid.intValue());
                    MonitoredVm target = host.getMonitoredVm(vmid);

                    StringMonitor cmdMonitor =
                            (StringMonitor)target.findByName("sun.rt.javaCommand");
                    String cmd = cmdMonitor.stringValue();

                    System.out.println("\t" + lvmid.intValue() + ": "
                                       + "\"" + cmd + "\"" + ": ");
                } catch (URISyntaxException e) {
                    System.err.println("Unexpected URISyntaxException: "
                                       + e.getMessage());
                } catch (MonitorException e) {
                    System.out.println("\t" + lvmid.intValue()
                                       + ": error reading monitoring data: "
                                       + " target possibly terminated?");
                }
            }
        }


        private int addStarted(Set<Integer> started) {
            int found = 0;
            for (Integer lvmid : started) {
                try {
                    VmIdentifier vmid = new VmIdentifier("//" + lvmid.intValue());
                    MonitoredVm target = host.getMonitoredVm(vmid);

                    StringMonitor cmdMonitor =
                            (StringMonitor)target.findByName("sun.rt.javaCommand");
                    String cmd = cmdMonitor.stringValue();

                    patternMatcher.reset(cmd);
                    System.out.print("Started: " + lvmid.intValue()
                                     + ": " + "\"" + cmd + "\"" + ": ");

                    if (patternMatcher.matches()) {
                        System.out.println("matches pattern - recorded");
                        targets.add(lvmid);
                        found++;
                    }
                    else {
                        System.out.println("does not match pattern - ignored");
                    }
                } catch (URISyntaxException e) {
                    System.err.println("Unexpected URISyntaxException: "
                                       + e.getMessage());
                } catch (MonitorException e) {
                    System.err.println("Unexpected MonitorException: "
                                       + e.getMessage());
                }
            }
            return found;
        }

        private int removeTerminated(Set<Integer> terminated) {
            int found = 0;
            for (Integer lvmid : terminated) {
                /*
                 * we don't attempt to attach to the target here as it's
                 * now dead and has no jvmstat share memory file. Just see
                 * if the process id is among those that we saved when we
                 * started the targets (note - duplicated allowed and somewhat
                 * expected on windows);
                 */
                System.out.print("Terminated: " + lvmid.intValue() + ": ");
                if (targets.contains(lvmid)) {
                    System.out.println("matches pattern - termination recorded");
                    targets.remove(lvmid);
                    found++;
                }
                else {
                    System.out.println("does not match pattern - ignored");
                }
            }
            return found;
        }

        @SuppressWarnings("unchecked")
        public void vmStatusChanged(VmStatusChangeEvent ev) {
            printList(ev.getActive(), "Active");
            printList(ev.getStarted(), "Started");
            printList(ev.getTerminated(), "Terminated");

            int recentlyStarted = addStarted(ev.getStarted());
            int recentlyTerminated = removeTerminated(ev.getTerminated());

            for (int i = 0; i < recentlyTerminated; i++) {
                terminateLatch.countDown();
            }
            for (int i = 0; i < recentlyStarted; i++) {
                startLatch.countDown();
            }
        }

        public void disconnected(HostEvent ev) {
        }
    }

    public static class SleeperStarter extends Thread {

        private final JavaProcess[] processes;
        private final int execInterval;
        private final String args;

        public SleeperStarter(int sleepers, int execInterval, String args) {
            this.execInterval = execInterval;
            this.args = args;
            this.processes = new JavaProcess[sleepers];
        }

        private synchronized int active() {
            int active = processes.length;
            for(JavaProcess jp : processes) {
                try {
                    jp.exitValue();
                    active--;
                } catch (IllegalThreadStateException e) {
                    // process hasn't exited yet
                }
            }
            return active;
        }

        public void run() {
           System.out.println("Starting " + processes.length + " sleepers");

           String[] classpath = {
               "-classpath",
               System.getProperty("java.class.path")
           };

           for (int i = 0; i < processes.length; i++) {
               try {
                   System.out.println("Starting Sleeper " + i);
                   synchronized(this) {
                       processes[i] = new JavaProcess("Sleeper", args + " " + i);
                       processes[i].addOptions(classpath);
                   }
                   processes[i].start();
                   Thread.sleep(execInterval);
               } catch (InterruptedException ignore) {
               } catch (IOException e) {
                   System.err.println(
                           "IOException trying to start Sleeper " + i + ": "
                           + e.getMessage());
               }
           }

           // spin waiting for the processes to terminate
           while (active() > 0) ;
        }
    }
}

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