Implement GC notifications as part of the monitoring command

3 files changed, 115 insertions, 6 deletions

diff --git a/spark-common/src/main/java/me/lucko/spark/common/GarbageCollectionMonitor.java b/spark-common/src/main/java/me/lucko/spark/common/GarbageCollectionMonitor.java
new file mode 100644
index 0000000..dd9931e
--- /dev/null
+++ b/spark-common/src/main/java/me/lucko/spark/common/GarbageCollectionMonitor.java
@@ -0,0 +1,77 @@
+/*
+ * This file is part of spark.
+ *
+ *  Copyright (c) lucko (Luck) <luck@lucko.me>
+ *  Copyright (c) contributors
+ *
+ *  This program is free software: you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation, either version 3 of the License, or
+ *  (at your option) any later version.
+ *
+ *  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.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+package me.lucko.spark.common;
+
+import com.sun.management.GarbageCollectionNotificationInfo;
+
+import java.lang.management.GarbageCollectorMXBean;
+import java.lang.management.ManagementFactory;
+import java.util.ArrayList;
+import java.util.List;
+
+import javax.management.ListenerNotFoundException;
+import javax.management.Notification;
+import javax.management.NotificationEmitter;
+import javax.management.NotificationListener;
+import javax.management.openmbean.CompositeData;
+
+public class GarbageCollectionMonitor implements NotificationListener, AutoCloseable {
+
+    private final TickMonitor tickMonitor;
+    private final List<NotificationEmitter> emitters = new ArrayList<>();
+
+    public GarbageCollectionMonitor(TickMonitor tickMonitor) {
+        this.tickMonitor = tickMonitor;
+
+        List<GarbageCollectorMXBean> beans = ManagementFactory.getGarbageCollectorMXBeans();
+        for (GarbageCollectorMXBean bean : beans) {
+            if (!(bean instanceof NotificationEmitter)) {
+                continue;
+            }
+
+            NotificationEmitter notificationEmitter = (NotificationEmitter) bean;
+            notificationEmitter.addNotificationListener(this, null, null);
+            this.emitters.add(notificationEmitter);
+        }
+    }
+
+    @Override
+    public void handleNotification(Notification notification, Object handback) {
+        if (!notification.getType().equals(GarbageCollectionNotificationInfo.GARBAGE_COLLECTION_NOTIFICATION)) {
+            return;
+        }
+
+        GarbageCollectionNotificationInfo data = GarbageCollectionNotificationInfo.from((CompositeData) notification.getUserData());
+        this.tickMonitor.onGc(data);
+    }
+
+    @Override
+    public void close() {
+        for (NotificationEmitter e : this.emitters) {
+            try {
+                e.removeNotificationListener(this);
+            } catch (ListenerNotFoundException ex) {
+                ex.printStackTrace();
+            }
+        }
+        this.emitters.clear();
+    }
+}
diff --git a/spark-common/src/main/java/me/lucko/spark/common/TickMonitor.java b/spark-common/src/main/java/me/lucko/spark/common/TickMonitor.java
index 98f7a28..6dc84ee 100644
--- a/spark-common/src/main/java/me/lucko/spark/common/TickMonitor.java
+++ b/spark-common/src/main/java/me/lucko/spark/common/TickMonitor.java
@@ -20,19 +20,22 @@
 
 package me.lucko.spark.common;
 
+import com.sun.management.GarbageCollectionNotificationInfo;
+
 import me.lucko.spark.profiler.TickCounter;
 
 import java.text.DecimalFormat;
 import java.util.DoubleSummaryStatistics;
 
-public abstract class TickMonitor implements Runnable {
+public abstract class TickMonitor implements Runnable, AutoCloseable {
     private static final DecimalFormat df = new DecimalFormat("#.##");
 
     private final TickCounter tickCounter;
+    private final GarbageCollectionMonitor garbageCollectionMonitor;
     private final int percentageChangeThreshold;
 
     // data
-    private double lastTickTime = 0;
+    private volatile double lastTickTime = 0;
     private State state = null;
     private DoubleSummaryStatistics averageTickTime = new DoubleSummaryStatistics();
     private double avg;
@@ -43,12 +46,16 @@ public abstract class TickMonitor implements Runnable {
 
         this.tickCounter.start();
         this.tickCounter.addTickTask(this);
+
+        this.garbageCollectionMonitor = new GarbageCollectionMonitor(this);
     }
 
     protected abstract void sendMessage(String message);
 
+    @Override
     public void close() {
         this.tickCounter.close();
+        this.garbageCollectionMonitor.close();
     }
 
     @Override
@@ -65,9 +72,15 @@ public abstract class TickMonitor implements Runnable {
         }
 
         // find the diff
-        double diff = now - this.lastTickTime;
+        double last = this.lastTickTime;
+        double diff = now - last;
+        boolean ignore = last == 0;
         this.lastTickTime = now;
 
+        if (ignore) {
+            return;
+        }
+
         // form averages
         if (this.state == State.SETUP) {
             this.averageTickTime.accept(diff);
@@ -95,12 +108,30 @@ public abstract class TickMonitor implements Runnable {
 
             double percentageChange = (increase * 100d) / this.avg;
             if (percentageChange > this.percentageChangeThreshold) {
-                sendMessage("&7Tick &8#" + this.tickCounter.getCurrentTick() + " &7lasted &b" + df.format(diff) + "&7 milliseconds. " +
-                        "&7(&b" + df.format(percentageChange) + "% &7increase from average)");
+                sendMessage("&7Tick &8#" + this.tickCounter.getCurrentTick() + " &7lasted &b" + df.format(diff) +
+                        "&7 ms. (&b" + df.format(percentageChange) + "% &7increase from average)");
             }
         }
     }
 
+    void onGc(GarbageCollectionNotificationInfo data) {
+        if (this.state == State.SETUP) {
+            // set lastTickTime to zero so this tick won't be counted in the average
+            this.lastTickTime = 0;
+            return;
+        }
+
+        String gcType = data.getGcAction();
+        if (gcType.equals("end of minor GC")) {
+            gcType = "Young Gen GC";
+        } else if (gcType.equals("end of major GC")) {
+            gcType = "Old Gen GC";
+        }
+
+        sendMessage("&7Tick &8#" + this.tickCounter.getCurrentTick() + " &7included &4GC &7lasting &b" +
+                df.format(data.getGcInfo().getDuration()) + "&7 ms. (type = " + gcType + ")");
+    }
+
     private enum State {
         SETUP,
         MONITORING
diff --git a/spark-common/src/main/java/me/lucko/spark/profiler/TickCounter.java b/spark-common/src/main/java/me/lucko/spark/profiler/TickCounter.java
index ac804f8..31d7f9a 100644
--- a/spark-common/src/main/java/me/lucko/spark/profiler/TickCounter.java
+++ b/spark-common/src/main/java/me/lucko/spark/profiler/TickCounter.java
@@ -23,7 +23,7 @@ package me.lucko.spark.profiler;
 /**
  * A hook with the game's "tick loop".
  */
-public interface TickCounter {
+public interface TickCounter extends AutoCloseable {
 
     /**
      * Starts the counter
@@ -33,6 +33,7 @@ public interface TickCounter {
     /**
      * Stops the counter
      */
+    @Override
     void close();
 
     /**