Subversion Repositories splitter

/*
 * Copyright (c) 2009.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 3 as
 * published by the Free Software Foundation.
 *
 * This program 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 for more details.
 */

package uk.me.parabola.splitter;

/**
 * Periodically outputs the elapsed time and amount of memory used by the VM
 *
 * @author Chris Miller
 */
public class JVMHealthMonitor {
        private JVMHealthMonitor() {
        }

        private static Thread statusThread;
        private static long startTime;

        /**
         * Starts a daemon thread that will periodically report the state of the JVM (heap usage).
         * This method just needs to be called once and there's nothing else to do. The background
         * thread will terminate automatically when the application exits.
         *
         * @param statusFrequency the number of seconds to sleep between each status update.
         */
        public static void start(final long statusFrequency) {
                if (statusThread != null) {
                        throw new IllegalStateException("A JVMHealthMonitor thread is already running. JVMHealthMonitor.start() must only be called once during the lifetime of an application.");
                }
                startTime = System.currentTimeMillis();
                statusThread = new Thread(new Runnable() {
                        @Override
                        public void run() {
                                int iter=0;
                                while (true) {
                                        iter++;
                                        if (iter%10 == 0) {
                                                System.out.println("***** Full GC *****");
                                                System.gc();
                                        }
                                        long maxMem = Runtime.getRuntime().maxMemory() / 1024 / 1024;
                                        long totalMem = Runtime.getRuntime().totalMemory() / 1024 / 1024;
                                        long freeMem = Runtime.getRuntime().freeMemory() / 1024 / 1024;
                                        long usedMem = totalMem - freeMem;
                                        System.out.println("Elapsed time: " + getElapsedTime() + "   Memory: Current " + totalMem + "MB (" + usedMem + "MB used, " + freeMem + "MB free) Max " + maxMem + "MB");
                                        try {
                                                Thread.sleep(statusFrequency * 1000L);
                                        }
                                        catch (InterruptedException e) {
                                                System.out.println("JVMHealthMonitor sleep was interrupted. Ignoring.");
                                        }
                                }
                        }
                }
                );
                statusThread.setDaemon(true);
                statusThread.setName("JVMHealthMonitor");
                statusThread.start();
        }

        private static String getElapsedTime() {
                long elapsed = (System.currentTimeMillis() - startTime) / 1000;
                long seconds = elapsed % 60;
                long minutes = elapsed / 60 % 60;
                long hours = elapsed / (60L * 60) % 60;
                StringBuilder buf = new StringBuilder(20);
                if (hours > 0)
                        buf.append(hours).append("h ");
                if (hours > 0 || minutes > 0)
                        buf.append(minutes).append("m ");
                buf.append(seconds).append('s');
                return buf.toString();
        }
}