GCMonitorTask.java

/*
 * Copyright (c) 2017. Starlis LLC / dba Empire Minecraft
 *
 * This source code is proprietary software and must not be redistributed without Starlis LLC's approval
 *
 */

package com.empireminecraft.systems.tasks;

import com.empireminecraft.util.Log;
import com.empireminecraft.util.MovingAverage;
import com.empireminecraft.util.TimeUtil;
import com.sun.management.GarbageCollectorMXBean;
import com.sun.management.GcInfo;

import javax.management.MBeanServer;
import java.lang.management.ManagementFactory;

@SuppressWarnings("WeakerAccess")
public class GCMonitorTask implements Runnable {
    private static volatile GarbageCollectorMXBean youngBean;
    private static volatile GarbageCollectorMXBean oldBean;
    public static long lastYoung = 0;
    public static long lastOld = 0;
    public static long oldCount = 0;
    public static MovingAverage youngInterval = new MovingAverage(10, TimeUtil.SECOND.inMilli(30));
    public static MovingAverage youngDuration = new MovingAverage(10, 50);
    static {
        MBeanServer server = ManagementFactory.getPlatformMBeanServer();
        try {
            String youngId = "java.lang:type=GarbageCollector,name=G1 Young Generation";
            youngBean = ManagementFactory.newPlatformMXBeanProxy(server, youngId, GarbageCollectorMXBean.class);
            if (youngBean == null) {
                Log.error("Could not find YoungGen Bean");
            } else {
                GcInfo lastGcInfo = youngBean.getLastGcInfo();
                if (lastGcInfo != null) {
                    lastYoung = lastGcInfo.getStartTime();
                } else {
                    lastYoung = System.currentTimeMillis();
                }
            }
            String oldId = "java.lang:type=GarbageCollector,name=G1 Old Generation";
            oldBean = ManagementFactory.newPlatformMXBeanProxy(server, oldId, GarbageCollectorMXBean.class);
            if (oldBean == null) {
                Log.error("Could not find OldGen Bean");
            } else {
                oldCount = oldBean.getCollectionCount();
                GcInfo lastGcInfo = oldBean.getLastGcInfo();
                if (lastGcInfo != null) {
                    lastOld = lastGcInfo.getStartTime();

                } else {
                    lastOld = 0;
                }
            }
        } catch (Exception e) {
            Log.exception(e);
        }
    }
    @Override
    public void run() {
        processYoung();
        processOld();
    }

    private static synchronized void processOld() {
        if (oldBean == null) {
            return;
        }
        GcInfo last = oldBean.getLastGcInfo();
        if (last == null) {
            return;
        }
        oldCount = oldBean.getCollectionCount();
        lastOld = last.getStartTime();
    }

    private static synchronized void processYoung() {
        if (youngBean == null) {
            return;
        }
        GcInfo last = youngBean.getLastGcInfo();
        if (last == null) {
            return;
        }
        long startTime = last.getStartTime();
        long endTime = last.getEndTime();
        if (startTime == endTime) {
            return;
        }
        if (lastYoung == startTime) {
            return;
        }

        long diff = startTime - lastYoung;
        long duration = endTime - startTime;
        lastYoung = startTime;
        youngInterval.add(diff);
        youngDuration.add(duration);
    }
}

MovingAverage.java

/*
 * Copyright (c) 2017. Starlis LLC / dba Empire Minecraft
 *
 * This source code is proprietary software and must not be redistributed without Starlis LLC's approval
 *
 */

package com.empireminecraft.util;

public class MovingAverage {
    private final double exp;
    private double avg;

    public MovingAverage(int size, double initial) {
        this.avg = initial;
        this.exp = (size-1D)/size;
    }

    public void add(double x) {
        avg = (avg * exp) + (x * (1 - exp));
    }

    public double getAverage() {
        return avg;
    }
}