Fix major memory leaks in ExpiringMap

computeIfAbsent would leak as the entry
was never registered into the ttl map

This fixes that ,as well as redesigns cleaning to
not run on every manipulation, and instead to run clean
once per tick per expiring map.

Spigot-Server-Patches/0372-Fix-major-memory-leaks-in-ExpiringMap.patch

@@ -0,0 +1,112 @@
+From c9297fde1beff53e303bb09caf0bb4b20c6792ce Mon Sep 17 00:00:00 2001
+From: Aikar <aikar@aikar.co>
+Date: Sun, 16 Sep 2018 00:00:16 -0400
+Subject: [PATCH] Fix major memory leaks in ExpiringMap
+
+computeIfAbsent would leak as the entry
+was never registered into the ttl map
+
+This fixes that ,as well as redesigns cleaning to
+not run on every manipulation, and instead to run clean
+once per tick per expiring map.
+
+diff --git a/src/main/java/net/minecraft/server/ExpiringMap.java b/src/main/java/net/minecraft/server/ExpiringMap.java
+index 4006f5a69c..5345b97241 100644
+--- a/src/main/java/net/minecraft/server/ExpiringMap.java
++++ b/src/main/java/net/minecraft/server/ExpiringMap.java
+@@ -6,25 +6,44 @@ import it.unimi.dsi.fastutil.longs.Long2ObjectOpenHashMap;
+ import it.unimi.dsi.fastutil.longs.Long2LongMap.Entry;
+ import it.unimi.dsi.fastutil.objects.ObjectIterator;
+ import java.util.Map;
++import java.util.function.LongFunction;
+ 
+ public class ExpiringMap<T> extends Long2ObjectOpenHashMap<T> {
+     private final int a;
+-    private final Long2LongMap b = new Long2LongLinkedOpenHashMap();
++    private final Long2LongMap ttl = new Long2LongLinkedOpenHashMap(); // Paper
+ 
+     public ExpiringMap(int i, int j) {
+         super(i);
+         this.a = j;
+     }
+ 
+-    private void a(long i) {
+-        long j = SystemUtils.b();
+-        this.b.put(i, j);
+-        ObjectIterator objectiterator = this.b.long2LongEntrySet().iterator();
++    // Paper start
++    private synchronized void setAccess(long i) { a(i); } // Paper - OBFHELPER
++    private synchronized void a(long i) {
++        long j = System.currentTimeMillis(); // Paper
++        this.ttl.put(i, j);
++        if (!registered) {
++            registered = true;
++            MinecraftServer.getServer().expiringMaps.add(this);
++        }
++    }
++
++    @Override
++    public synchronized T computeIfAbsent(long l, LongFunction<? extends T> longFunction) {
++        setAccess(l);
++        return super.computeIfAbsent(l, longFunction);
++    }
++    private boolean registered = false;
++
++    // Break clean to its own method to be ticked
++    synchronized boolean clean() {
++        long now = System.currentTimeMillis();
++        ObjectIterator<Long2LongMap.Entry> objectiterator = this.ttl.long2LongEntrySet().iterator(); // Paper
+ 
+         while(objectiterator.hasNext()) {
+-            Entry entry = (Entry)objectiterator.next();
+-            Object object = super.get(entry.getLongKey());
+-            if (j - entry.getLongValue() <= (long)this.a) {
++            Long2LongMap.Entry entry = objectiterator.next(); // Paper
++            T object = super.get(entry.getLongKey()); // Paper
++            if (now - entry.getLongValue() <= (long)this.a) {
+                 break;
+             }
+ 
+@@ -33,7 +52,18 @@ public class ExpiringMap<T> extends Long2ObjectOpenHashMap<T> {
+                 objectiterator.remove();
+             }
+         }
+-
++        if (this.ttl.size() != this.size) {
++            MinecraftServer.LOGGER.error("WARNING: ExpiringMap desync - Memory leak risk!");
++            for (Entry<T> entry : this.entries) {
++                ttl.putIfAbsent(entry.getLongKey(), now);
++            }
++        }
++        if (isEmpty()) {
++            registered = false;
++            return true;
++        }
++        return false;
++        // Paper end
+     }
+ 
+     protected boolean a(T var1) {
+diff --git a/src/main/java/net/minecraft/server/MinecraftServer.java b/src/main/java/net/minecraft/server/MinecraftServer.java
+index 80e8b023cf..70a609efcc 100644
+--- a/src/main/java/net/minecraft/server/MinecraftServer.java
++++ b/src/main/java/net/minecraft/server/MinecraftServer.java
+@@ -155,6 +155,7 @@ public abstract class MinecraftServer implements IAsyncTaskHandler, IMojangStati
+     public int autosavePeriod;
+     public File bukkitDataPackFolder;
+     public CommandDispatcher vanillaCommandDispatcher;
++    public List<ExpiringMap> expiringMaps = java.util.Collections.synchronizedList(new java.util.ArrayList<>()); // PAper
+     // CraftBukkit end
+     // Spigot start
+     public static final int TPS = 20;
+@@ -995,6 +996,7 @@ public abstract class MinecraftServer implements IAsyncTaskHandler, IMojangStati
+         this.methodProfiler.e();
+         org.spigotmc.WatchdogThread.tick(); // Spigot
+         PaperLightingQueue.processQueue(startTime); // Paper
++        expiringMaps.removeIf(ExpiringMap::clean); // Paper
+         this.slackActivityAccountant.tickEnded(l); // Spigot
+         co.aikar.timings.TimingsManager.FULL_SERVER_TICK.stopTiming(); // Paper
+     }
+-- 
+2.19.0
+