From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Spottedleaf <Spottedleaf@users.noreply.github.com>
Date: Fri, 19 Jul 2019 03:29:14 -0700
Subject: [PATCH] Add debug for sync chunk loads

This patch adds a tool to find calls to getChunkAt which would load
chunks, however it must be enabled by setting the startup flag
-Dpaper.debug-sync-loads=true

- To get a debug log for sync loads, the command is
  /paper syncloadinfo
- To clear clear the currently stored sync load info, use
  /paper syncloadinfo clear

diff --git a/src/main/java/com/destroystokyo/paper/io/SyncLoadFinder.java b/src/main/java/com/destroystokyo/paper/io/SyncLoadFinder.java
new file mode 100644
index 0000000000000000000000000000000000000000..404a8fd128043527d23f22ee26f7c8c739f09089
--- /dev/null
+++ b/src/main/java/com/destroystokyo/paper/io/SyncLoadFinder.java
@@ -0,0 +1,175 @@
+package com.destroystokyo.paper.io;
+
+import com.google.gson.JsonArray;
+import com.google.gson.JsonObject;
+import com.mojang.datafixers.util.Pair;
+import it.unimi.dsi.fastutil.longs.Long2IntMap;
+import it.unimi.dsi.fastutil.longs.Long2IntOpenHashMap;
+import it.unimi.dsi.fastutil.objects.Object2ObjectOpenHashMap;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Map;
+import java.util.WeakHashMap;
+import net.minecraft.world.level.Level;
+
+public class SyncLoadFinder {
+
+    public static final boolean ENABLED = Boolean.getBoolean("paper.debug-sync-loads");
+
+    private static final WeakHashMap<Level, Object2ObjectOpenHashMap<ThrowableWithEquals, SyncLoadInformation>> SYNC_LOADS = new WeakHashMap<>();
+
+    private static final class SyncLoadInformation {
+
+        public int times;
+
+        public final Long2IntOpenHashMap coordinateTimes = new Long2IntOpenHashMap();
+    }
+
+    public static void clear() {
+        SYNC_LOADS.clear();
+    }
+
+    public static void logSyncLoad(final Level world, final int chunkX, final int chunkZ) {
+        if (!ENABLED) {
+            return;
+        }
+
+        final ThrowableWithEquals stacktrace = new ThrowableWithEquals(Thread.currentThread().getStackTrace());
+
+        SYNC_LOADS.compute(world, (final Level keyInMap, Object2ObjectOpenHashMap<ThrowableWithEquals, SyncLoadInformation> map) -> {
+            if (map == null) {
+                map = new Object2ObjectOpenHashMap<>();
+            }
+
+            map.compute(stacktrace, (ThrowableWithEquals keyInMap0, SyncLoadInformation valueInMap) -> {
+                if (valueInMap == null) {
+                    valueInMap = new SyncLoadInformation();
+                }
+
+                ++valueInMap.times;
+
+                valueInMap.coordinateTimes.compute(io.papermc.paper.util.MCUtil.getCoordinateKey(chunkX, chunkZ), (Long keyInMap1, Integer valueInMap1) -> {
+                    return valueInMap1 == null ? Integer.valueOf(1) : Integer.valueOf(valueInMap1.intValue() + 1);
+                });
+
+                return valueInMap;
+            });
+
+            return map;
+        });
+    }
+
+    public static JsonObject serialize() {
+        final JsonObject ret = new JsonObject();
+
+        final JsonArray worldsData = new JsonArray();
+
+        for (final Map.Entry<Level, Object2ObjectOpenHashMap<ThrowableWithEquals, SyncLoadInformation>> entry : SYNC_LOADS.entrySet()) {
+            final Level world = entry.getKey();
+
+            final JsonObject worldData = new JsonObject();
+
+            worldData.addProperty("name", world.getWorld().getName());
+
+            final List<Pair<ThrowableWithEquals, SyncLoadInformation>> data = new ArrayList<>();
+
+            entry.getValue().forEach((ThrowableWithEquals stacktrace, SyncLoadInformation times) -> {
+                data.add(new Pair<>(stacktrace, times));
+            });
+
+            data.sort((Pair<ThrowableWithEquals, SyncLoadInformation> pair1, Pair<ThrowableWithEquals, SyncLoadInformation> pair2) -> {
+                return Integer.compare(pair2.getSecond().times, pair1.getSecond().times); // reverse order
+            });
+
+            final JsonArray stacktraces = new JsonArray();
+
+            for (Pair<ThrowableWithEquals, SyncLoadInformation> pair : data) {
+                final JsonObject stacktrace = new JsonObject();
+
+                stacktrace.addProperty("times", pair.getSecond().times);
+
+                final JsonArray traces = new JsonArray();
+
+                for (StackTraceElement element : pair.getFirst().stacktrace) {
+                    traces.add(String.valueOf(element));
+                }
+
+                stacktrace.add("stacktrace", traces);
+
+                final JsonArray coordinates = new JsonArray();
+
+                for (Long2IntMap.Entry coordinate : pair.getSecond().coordinateTimes.long2IntEntrySet()) {
+                    final long key = coordinate.getLongKey();
+                    final int times = coordinate.getIntValue();
+                    coordinates.add("(" + io.papermc.paper.util.MCUtil.getCoordinateX(key) + "," + io.papermc.paper.util.MCUtil.getCoordinateZ(key) + "): " + times);
+                }
+
+                stacktrace.add("coordinates", coordinates);
+
+                stacktraces.add(stacktrace);
+            }
+
+
+            worldData.add("stacktraces", stacktraces);
+            worldsData.add(worldData);
+        }
+
+        ret.add("worlds", worldsData);
+
+        return ret;
+    }
+
+    static final class ThrowableWithEquals {
+
+        private final StackTraceElement[] stacktrace;
+        private final int hash;
+
+        public ThrowableWithEquals(final StackTraceElement[] stacktrace) {
+            this.stacktrace = stacktrace;
+            this.hash = ThrowableWithEquals.hash(stacktrace);
+        }
+
+        public static int hash(final StackTraceElement[] stacktrace) {
+            int hash = 0;
+
+            for (int i = 0; i < stacktrace.length; ++i) {
+                hash *= 31;
+                hash += stacktrace[i].hashCode();
+            }
+
+            return hash;
+        }
+
+        @Override
+        public int hashCode() {
+            return this.hash;
+        }
+
+        @Override
+        public boolean equals(final Object obj) {
+            if (obj == null || obj.getClass() != this.getClass()) {
+                return false;
+            }
+
+            final ThrowableWithEquals other = (ThrowableWithEquals)obj;
+            final StackTraceElement[] otherStackTrace = other.stacktrace;
+
+            if (this.stacktrace.length != otherStackTrace.length || this.hash != other.hash) {
+                return false;
+            }
+
+            if (this == obj) {
+                return true;
+            }
+
+            for (int i = 0; i < this.stacktrace.length; ++i) {
+                if (!this.stacktrace[i].equals(otherStackTrace[i])) {
+                    return false;
+                }
+            }
+
+            return true;
+        }
+    }
+}
diff --git a/src/main/java/io/papermc/paper/command/PaperCommand.java b/src/main/java/io/papermc/paper/command/PaperCommand.java
index 69ffd6ea2ce7c6d4f211c6081fcea79afd7eac6c..69d093d3450931038ac3d27d7874060d13dc2225 100644
--- a/src/main/java/io/papermc/paper/command/PaperCommand.java
+++ b/src/main/java/io/papermc/paper/command/PaperCommand.java
@@ -38,6 +38,7 @@ public final class PaperCommand extends Command {
         commands.put(Set.of("reload"), new ReloadCommand());
         commands.put(Set.of("version"), new VersionCommand());
         commands.put(Set.of("dumpplugins"), new DumpPluginsCommand());
+        commands.put(Set.of("syncloadinfo"), new SyncLoadInfoCommand());
 
         return commands.entrySet().stream()
             .flatMap(entry -> entry.getKey().stream().map(s -> Map.entry(s, entry.getValue())))
diff --git a/src/main/java/io/papermc/paper/command/subcommands/SyncLoadInfoCommand.java b/src/main/java/io/papermc/paper/command/subcommands/SyncLoadInfoCommand.java
new file mode 100644
index 0000000000000000000000000000000000000000..95d6022c9cfb2e36ec5a71be6e34354027c2ec08
--- /dev/null
+++ b/src/main/java/io/papermc/paper/command/subcommands/SyncLoadInfoCommand.java
@@ -0,0 +1,88 @@
+package io.papermc.paper.command.subcommands;
+
+import com.destroystokyo.paper.io.SyncLoadFinder;
+import com.google.gson.JsonObject;
+import com.google.gson.internal.Streams;
+import com.google.gson.stream.JsonWriter;
+import io.papermc.paper.command.CommandUtil;
+import io.papermc.paper.command.PaperSubcommand;
+import java.io.File;
+import java.io.FileOutputStream;
+import java.io.PrintStream;
+import java.io.StringWriter;
+import java.nio.charset.StandardCharsets;
+import java.time.LocalDateTime;
+import java.time.format.DateTimeFormatter;
+import java.util.List;
+
+import net.kyori.adventure.text.event.ClickEvent;
+import net.kyori.adventure.text.event.HoverEvent;
+import net.minecraft.server.MinecraftServer;
+import org.bukkit.command.CommandSender;
+import org.checkerframework.checker.nullness.qual.NonNull;
+import org.checkerframework.framework.qual.DefaultQualifier;
+
+import static net.kyori.adventure.text.Component.text;
+import static net.kyori.adventure.text.format.NamedTextColor.GRAY;
+import static net.kyori.adventure.text.format.NamedTextColor.GREEN;
+import static net.kyori.adventure.text.format.NamedTextColor.RED;
+import static net.kyori.adventure.text.format.NamedTextColor.WHITE;
+
+@DefaultQualifier(NonNull.class)
+public final class SyncLoadInfoCommand implements PaperSubcommand {
+    @Override
+    public boolean execute(final CommandSender sender, final String subCommand, final String[] args) {
+        this.doSyncLoadInfo(sender, args);
+        return true;
+    }
+
+    @Override
+    public List<String> tabComplete(final CommandSender sender, final String subCommand, final String[] args) {
+        return CommandUtil.getListMatchingLast(sender, args, "clear");
+    }
+
+    private static final DateTimeFormatter FORMATTER = DateTimeFormatter.ofPattern("yyyy-MM-dd_HH.mm.ss");
+
+    private void doSyncLoadInfo(final CommandSender sender, final String[] args) {
+        if (!SyncLoadFinder.ENABLED) {
+            String systemFlag = "-Dpaper.debug-sync-loads=true";
+            sender.sendMessage(text().color(RED).append(text("This command requires the server startup flag '")).append(
+                text(systemFlag, WHITE).clickEvent(ClickEvent.copyToClipboard(systemFlag))
+                                       .hoverEvent(HoverEvent.showText(text("Click to copy the system flag")))).append(
+                text("' to be set.")));
+            return;
+        }
+
+        if (args.length > 0 && args[0].equals("clear")) {
+            SyncLoadFinder.clear();
+            sender.sendMessage(text("Sync load data cleared.", GRAY));
+            return;
+        }
+
+        File file = new File(new File(new File("."), "debug"),
+            "sync-load-info-" + FORMATTER.format(LocalDateTime.now()) + ".txt");
+        file.getParentFile().mkdirs();
+        sender.sendMessage(text("Writing sync load info to " + file, GREEN));
+
+
+        try {
+            final JsonObject data = SyncLoadFinder.serialize();
+
+            StringWriter stringWriter = new StringWriter();
+            JsonWriter jsonWriter = new JsonWriter(stringWriter);
+            jsonWriter.setIndent(" ");
+            jsonWriter.setLenient(false);
+            Streams.write(data, jsonWriter);
+
+            try (
+                PrintStream out = new PrintStream(new FileOutputStream(file), false, StandardCharsets.UTF_8)
+            ) {
+                out.print(stringWriter);
+            }
+            sender.sendMessage(text("Successfully written sync load information!", GREEN));
+        } catch (Throwable thr) {
+            sender.sendMessage(text("Failed to write sync load information! See the console for more info.", RED));
+            MinecraftServer.LOGGER.warn("Error occurred while dumping sync chunk load info", thr);
+        }
+    }
+}
diff --git a/src/main/java/net/minecraft/server/level/ServerChunkCache.java b/src/main/java/net/minecraft/server/level/ServerChunkCache.java
index d41c0e4474d057c7b13427bfd896c50f24232615..2d9d4d06b75873f888ef4d8f5779a52706f821a8 100644
--- a/src/main/java/net/minecraft/server/level/ServerChunkCache.java
+++ b/src/main/java/net/minecraft/server/level/ServerChunkCache.java
@@ -279,6 +279,7 @@ public class ServerChunkCache extends ChunkSource {
 
             Objects.requireNonNull(completablefuture);
             if (!completablefuture.isDone()) { // Paper
+                com.destroystokyo.paper.io.SyncLoadFinder.logSyncLoad(this.level, x, z); // Paper - Add debug for sync chunk loads
                 this.level.timings.syncChunkLoad.startTiming(); // Paper
             chunkproviderserver_b.managedBlock(completablefuture::isDone);
                 this.level.timings.syncChunkLoad.stopTiming(); // Paper
diff --git a/src/main/java/net/minecraft/server/level/ServerLevel.java b/src/main/java/net/minecraft/server/level/ServerLevel.java
index 51644c24900600d95c3f6df073769b68be702b2d..1170a0031368ede2e45d24720506f6519cbd55da 100644
--- a/src/main/java/net/minecraft/server/level/ServerLevel.java
+++ b/src/main/java/net/minecraft/server/level/ServerLevel.java
@@ -421,6 +421,13 @@ public class ServerLevel extends Level implements WorldGenLevel {
         this.getCraftServer().addWorld(this.getWorld()); // CraftBukkit
     }
 
+    // Paper start
+    @Override
+    public boolean hasChunk(int chunkX, int chunkZ) {
+        return this.getChunkSource().getChunkAtIfLoadedImmediately(chunkX, chunkZ) != null;
+    }
+    // Paper end
+
     /** @deprecated */
     @Deprecated
     @VisibleForTesting
