Paper/patches/server/0137-Do-not-submit-profile-lookups-to-worldgen-threads.patch

From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Spottedleaf <Spottedleaf@users.noreply.github.com>
Date: Sun, 8 Aug 2021 16:26:46 -0700
Subject: [PATCH] Do not submit profile lookups to worldgen threads

They block. On network I/O.

If enough tasks are submitted the server will eventually stall
out due to a sync load, as the worldgen threads will be
stalling on profile lookups.

diff --git a/src/main/java/net/minecraft/Util.java b/src/main/java/net/minecraft/Util.java
index 9d91e7890d8cba72f0aa2ca9661f6de7ae8a0dcd..cf54e2c8e8aadb9e7343382a5ba59c657234c9b9 100644
--- a/src/main/java/net/minecraft/Util.java
+++ b/src/main/java/net/minecraft/Util.java
@@ -93,6 +93,22 @@ public class Util {
     private static final ExecutorService BACKGROUND_EXECUTOR = makeExecutor("Main");
     private static final ExecutorService IO_POOL = makeIoExecutor("IO-Worker-", false);
     private static final ExecutorService DOWNLOAD_POOL = makeIoExecutor("Download-", true);
+    // Paper start - don't submit BLOCKING PROFILE LOOKUPS to the world gen thread
+    public static final ExecutorService PROFILE_EXECUTOR = Executors.newFixedThreadPool(2, new java.util.concurrent.ThreadFactory() {
+
+        private final AtomicInteger count = new AtomicInteger();
+
+        @Override
+        public Thread newThread(Runnable run) {
+            Thread ret = new Thread(run);
+            ret.setName("Profile Lookup Executor #" + this.count.getAndIncrement());
+            ret.setUncaughtExceptionHandler((Thread thread, Throwable throwable) -> {
+                LOGGER.error("Uncaught exception in thread " + thread.getName(), throwable);
+            });
+            return ret;
+        }
+    });
+    // Paper end - don't submit BLOCKING PROFILE LOOKUPS to the world gen thread
     private static final DateTimeFormatter FILENAME_DATE_TIME_FORMATTER = DateTimeFormatter.ofPattern("yyyy-MM-dd_HH.mm.ss", Locale.ROOT);
     public static final int LINEAR_LOOKUP_THRESHOLD = 8;
     public static final long NANOS_PER_MILLI = 1000000L;
diff --git a/src/main/java/net/minecraft/server/players/GameProfileCache.java b/src/main/java/net/minecraft/server/players/GameProfileCache.java
index aeb0c7ce9b6f93dadd407dbdefba053568f2e2fe..416b26c2ab62b29d640169166980e398d5824b14 100644
--- a/src/main/java/net/minecraft/server/players/GameProfileCache.java
+++ b/src/main/java/net/minecraft/server/players/GameProfileCache.java
@@ -169,7 +169,7 @@ public class GameProfileCache {
             } else {
                 CompletableFuture<Optional<GameProfile>> completablefuture1 = CompletableFuture.supplyAsync(() -> {
                     return this.get(username);
-                }, Util.backgroundExecutor()).whenCompleteAsync((optional, throwable) -> {
+                }, Util.PROFILE_EXECUTOR).whenCompleteAsync((optional, throwable) -> { // Paper - don't submit BLOCKING PROFILE LOOKUPS to the world gen thread
                     this.requests.remove(username);
                 }, this.executor);
 
diff --git a/src/main/java/net/minecraft/world/level/block/entity/SkullBlockEntity.java b/src/main/java/net/minecraft/world/level/block/entity/SkullBlockEntity.java
index 6097e0ab387cfa4c2c9ab0389fc5bb6cd899ecc3..ebba6bc5b337d19e32be5a78294501ed8300f2bd 100644
--- a/src/main/java/net/minecraft/world/level/block/entity/SkullBlockEntity.java
+++ b/src/main/java/net/minecraft/world/level/block/entity/SkullBlockEntity.java
@@ -105,7 +105,7 @@ public class SkullBlockEntity extends BlockEntity {
                 ProfileResult profileResult = apiServices.sessionService().fetchProfile(uuid, true);
                 return Optional.ofNullable(profileResult).map(ProfileResult::profile);
             }
-        }, Util.backgroundExecutor());
+        }, Util.PROFILE_EXECUTOR); // Paper - don't submit BLOCKING PROFILE LOOKUPS to the world gen thread
     }
 
     public static void clear() {
diff --git a/src/main/java/org/bukkit/craftbukkit/profile/CraftPlayerProfile.java b/src/main/java/org/bukkit/craftbukkit/profile/CraftPlayerProfile.java
index 44174c5a7b255af489c1e4bf589299e6bdbb90a3..ab18b1d480f7ecc0ad9a51471d8f45b0da74d8cf 100644
--- a/src/main/java/org/bukkit/craftbukkit/profile/CraftPlayerProfile.java
+++ b/src/main/java/org/bukkit/craftbukkit/profile/CraftPlayerProfile.java
@@ -136,7 +136,7 @@ public final class CraftPlayerProfile implements PlayerProfile {
 
     @Override
     public CompletableFuture<PlayerProfile> update() {
-        return CompletableFuture.supplyAsync(this::getUpdatedProfile, Util.backgroundExecutor());
+        return CompletableFuture.supplyAsync(this::getUpdatedProfile, Util.PROFILE_EXECUTOR); // Paper - don't submit BLOCKING PROFILE LOOKUPS to the world gen thread
     }
 
     private CraftPlayerProfile getUpdatedProfile() {