以编程方式捕获完整GC计数

Question

我试图捕获Java应用程序中出现的完整GCs。到目前为止，我有两种方法，都有缺陷：

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编辑：为了明确起见，我想在给定的JVM中捕获这些信息。这个JVM由一个单独的团队控制，我们不需要控制他们将设置的JVM参数，我们只能提出建议。这个想法类似于飞行记录器，而是向管理员实时提供信息。

Answer 1

您可以侦听GC通知。请参见下面的代码。

我在这里交叉了这个答案，因为它似乎相关。根据@the8472在这个问题中给出的指针，我制作了一个更完整的示例，用于从JVM内部记录GC（从而检测/计数）。我希望这能为某人节省一些时间：）

package fi.pelam.gclogutil;
import java.lang.management.*;
import java.util.Map;
import javax.management.openmbean.CompositeData;
import javax.management.*;

import com.sun.management.GarbageCollectionNotificationInfo;
import com.sun.management.GcInfo;

public class GcLogUtil {
    static public void startLoggingGc() {
        // http://www.programcreek.com/java-api-examples/index.php?class=javax.management.MBeanServerConnection&method=addNotificationListener
        // https://docs.oracle.com/javase/8/docs/jre/api/management/extension/com/sun/management/GarbageCollectionNotificationInfo.html#GARBAGE_COLLECTION_NOTIFICATION
        for (GarbageCollectorMXBean gcMbean : ManagementFactory.getGarbageCollectorMXBeans()) {
            try {
                ManagementFactory.getPlatformMBeanServer().
                        addNotificationListener(gcMbean.getObjectName(), listener, null,null);
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
    }

    static private NotificationListener listener = new NotificationListener() {
        @Override
        public void handleNotification(Notification notification, Object handback) {
            if (notification.getType().equals(GarbageCollectionNotificationInfo.GARBAGE_COLLECTION_NOTIFICATION)) {
                // https://docs.oracle.com/javase/8/docs/jre/api/management/extension/com/sun/management/GarbageCollectionNotificationInfo.html
                CompositeData cd = (CompositeData) notification.getUserData();
                GarbageCollectionNotificationInfo gcNotificationInfo = GarbageCollectionNotificationInfo.from(cd);
                GcInfo gcInfo = gcNotificationInfo.getGcInfo();
                System.out.println("GarbageCollection: "+
                        gcNotificationInfo.getGcAction() + " " +
                        gcNotificationInfo.getGcName() +
                        " duration: " + gcInfo.getDuration() + "ms" +
                        " used: " + sumUsedMb(gcInfo.getMemoryUsageBeforeGc()) + "MB" +
                        " -> " + sumUsedMb(gcInfo.getMemoryUsageAfterGc()) + "MB");
            }
        }
    };

    static private long sumUsedMb(Map<String, MemoryUsage> memUsages) {
        long sum = 0;
        for (MemoryUsage memoryUsage : memUsages.values()) {
            sum += memoryUsage.getUsed();
        }
        return sum / (1024 * 1024);
    }
}