Paper-Old/Spigot-Server-Patches/0356-Fix-concurrency-and-performance-issues-in-DataFixers.patch

From 0e2f5e014cc3c60ca147438cfadc46d2ba35af18 Mon Sep 17 00:00:00 2001
From: Aikar <aikar@aikar.co>
Date: Mon, 3 Sep 2018 22:18:38 -0400
Subject: [PATCH] Fix concurrency and performance issues in DataFixers

We are seeing issues with DataFixers being not thread safe in async chunks
and even in some spigot packet sending code.

There are a few more global objects that are mutated that need to
be synchronized to be safe for use over multiple threads.

There may be more cases, but these are extremely obvious ones.

Also replaced quite a few bad uses of Map.containsKey

containsKey is a common newbie mistake that "reads" cleaner, but
results in double the performance cost of all map operations as
containsKey in MOST cases where null values are not used is identical to get() == null

Considering how deep datafixers go in call stacks, with tons of map lookups,
this micro optimization could provide some gains.

Additionally, many of the containsKey/get/put style operations were
also a concurrency risk, resulting in multiple computation/insertions.

diff --git a/src/main/java/com/mojang/datafixers/DataFixerUpper.java b/src/main/java/com/mojang/datafixers/DataFixerUpper.java
index fb2c380f8a..a4922a35a2 100644
--- a/src/main/java/com/mojang/datafixers/DataFixerUpper.java
+++ b/src/main/java/com/mojang/datafixers/DataFixerUpper.java
@@ -65,7 +65,7 @@ public class DataFixerUpper implements DataFixer {
     private final Int2ObjectSortedMap<Schema> schemas;
     private final List<DataFix> globalList;
     private final IntSortedSet fixerVersions;
-    private final Long2ObjectMap<TypeRewriteRule> rules = new Long2ObjectOpenHashMap<>();
+    private final Long2ObjectMap<TypeRewriteRule> rules = it.unimi.dsi.fastutil.longs.Long2ObjectMaps.synchronize(new Long2ObjectOpenHashMap<>()); // Paper
 
     protected DataFixerUpper(final Int2ObjectSortedMap<Schema> schemas, final List<DataFix> globalList, final IntSortedSet fixerVersions) {
         this.schemas = schemas;
@@ -125,7 +125,7 @@ public class DataFixerUpper implements DataFixer {
         final int expandedDataVersion = DataFixUtils.makeKey(dataVersion);
 
         final long key = (long) expandedVersion << 32 | expandedDataVersion;
-        if (!rules.containsKey(key)) {
+        return rules.computeIfAbsent(key, k -> { // Paper
             final List<TypeRewriteRule> rules = Lists.newArrayList();
             for (final DataFix fix : globalList) {
                 final int fixVersion = fix.getVersionKey();
@@ -137,9 +137,8 @@ public class DataFixerUpper implements DataFixer {
                     rules.add(fixRule);
                 }
             }
-            this.rules.put(key, TypeRewriteRule.seq(rules));
-        }
-        return rules.get(key);
+            return TypeRewriteRule.seq(rules); // Paper
+        }); // Paper
     }
 
     protected IntSortedSet fixerVersions() {
diff --git a/src/main/java/com/mojang/datafixers/NamedChoiceFinder.java b/src/main/java/com/mojang/datafixers/NamedChoiceFinder.java
index 2c259d74e9..17481fb6e6 100644
--- a/src/main/java/com/mojang/datafixers/NamedChoiceFinder.java
+++ b/src/main/java/com/mojang/datafixers/NamedChoiceFinder.java
@@ -71,8 +71,10 @@ final class NamedChoiceFinder<FT> implements OpticFinder<FT> {
             }*/
             if (targetType instanceof TaggedChoice.TaggedChoiceType<?>) {
                 final TaggedChoice.TaggedChoiceType<?> choiceType = (TaggedChoice.TaggedChoiceType<?>) targetType;
-                if (choiceType.types().containsKey(name)) {
-                    final Type<?> elementType = choiceType.types().get(name);
+                // Paper start - performance - don't use containsKey
+                final Type<?> elementType = choiceType.types().get(name);
+                if (elementType != null) {
+                    // Paper end
                     if (!Objects.equals(type, elementType)) {
                         return Either.right(new Type.FieldNotFoundException(String.format("Type error for choice type \"%s\": expected type: %s, actual type: %s)", name, targetType, elementType)));
                     }
diff --git a/src/main/java/com/mojang/datafixers/functions/PointFree.java b/src/main/java/com/mojang/datafixers/functions/PointFree.java
index 0d88490f77..028942b8ea 100644
--- a/src/main/java/com/mojang/datafixers/functions/PointFree.java
+++ b/src/main/java/com/mojang/datafixers/functions/PointFree.java
@@ -14,7 +14,7 @@ public abstract class PointFree<T> {
     private Function<DynamicOps<?>, T> value;
 
     @SuppressWarnings("ConstantConditions")
-    public Function<DynamicOps<?>, T> evalCached() {
+    public synchronized Function<DynamicOps<?>, T> evalCached() { // Paper
         if (!initialized) {
             initialized = true;
             value = eval();
diff --git a/src/main/java/com/mojang/datafixers/schemas/Schema.java b/src/main/java/com/mojang/datafixers/schemas/Schema.java
index 7c67d989e0..7faca88a88 100644
--- a/src/main/java/com/mojang/datafixers/schemas/Schema.java
+++ b/src/main/java/com/mojang/datafixers/schemas/Schema.java
@@ -20,8 +20,8 @@ import java.util.function.Function;
 import java.util.function.Supplier;
 
 public class Schema {
-    protected final Object2IntMap<String> RECURSIVE_TYPES = new Object2IntOpenHashMap<>();
-    private final Map<String, Supplier<TypeTemplate>> TYPE_TEMPLATES = Maps.newHashMap();
+    protected final Object2IntMap<String> RECURSIVE_TYPES = it.unimi.dsi.fastutil.objects.Object2IntMaps.synchronize(new Object2IntOpenHashMap<>()); // Paper
+    private final Map<String, Supplier<TypeTemplate>> TYPE_TEMPLATES = Maps.newConcurrentMap(); // Paper
     private final Map<String, Type<?>> TYPES;
     private final int versionKey;
     private final String name;
@@ -37,26 +37,31 @@ public class Schema {
     }
 
     protected Map<String, Type<?>> buildTypes() {
-        final Map<String, Type<?>> types = Maps.newHashMap();
+        final Map<String, Type<?>> types = Maps.newConcurrentMap(); // Paper
 
         final List<TypeTemplate> templates = Lists.newArrayList();
 
+        synchronized (RECURSIVE_TYPES) { // Paper
         for (final Object2IntMap.Entry<String> entry : RECURSIVE_TYPES.object2IntEntrySet()) {
             templates.add(DSL.check(entry.getKey(), entry.getIntValue(), getTemplate(entry.getKey())));
-        }
+        } } // Paper
 
         final TypeTemplate choice = templates.stream().reduce(DSL::or).get();
         final TypeFamily family = new RecursiveTypeFamily(name, choice);
 
+        synchronized (TYPE_TEMPLATES) { // Paper
         for (final String name : TYPE_TEMPLATES.keySet()) {
             final Type<?> type;
-            if (RECURSIVE_TYPES.containsKey(name)) {
-                type = family.apply(RECURSIVE_TYPES.getInt(name));
+            // Paper start - concurrency and performance improvement, don't use containsKey
+            int recurseId = RECURSIVE_TYPES.getOrDefault(name, -1);
+            if (recurseId != -1) {
+                type = family.apply(recurseId);
+                // Paper end
             } else {
                 type = getTemplate(name).apply(family).apply(-1);
             }
             types.put(name, type);
-        }
+        } } // Paper
         return types;
     }
 
@@ -89,8 +94,11 @@ public class Schema {
     }
 
     public TypeTemplate id(final String name) {
-        if (RECURSIVE_TYPES.containsKey(name)) {
-            return DSL.id(RECURSIVE_TYPES.get(name));
+        // Paper start - improve concurrency and performance
+        int id = RECURSIVE_TYPES.getOrDefault(name, -1);
+        if (id != -1) {
+            return DSL.id(id);
+            // Paper end
         }
         return getTemplate(name);
     }
@@ -138,9 +146,10 @@ public class Schema {
     public void registerType(final boolean recursive, final DSL.TypeReference type, final Supplier<TypeTemplate> template) {
         TYPE_TEMPLATES.put(type.typeName(), template);
         // TODO: calculate recursiveness instead of hardcoding
+        synchronized (RECURSIVE_TYPES) { // Paper
         if (recursive && !RECURSIVE_TYPES.containsKey(type.typeName())) {
             RECURSIVE_TYPES.put(type.typeName(), RECURSIVE_TYPES.size());
-        }
+        } } // Paper
     }
 
     public int getVersionKey() {
diff --git a/src/main/java/com/mojang/datafixers/types/DynamicOps.java b/src/main/java/com/mojang/datafixers/types/DynamicOps.java
index 3c76929f24..f21531b3cd 100644
--- a/src/main/java/com/mojang/datafixers/types/DynamicOps.java
+++ b/src/main/java/com/mojang/datafixers/types/DynamicOps.java
@@ -151,10 +151,10 @@ public interface DynamicOps<T> {
 
     default Optional<T> getGeneric(final T input, final T key) {
         return getMapValues(input).flatMap(map -> {
-            if (map.containsKey(key)) {
-                return Optional.of(map.get(key));
-            }
-            return Optional.empty();
+            // Paper start - performance - don't use containsKey
+            T value = map.get(key);
+            return value != null ? Optional.of(value) : Optional.empty();
+            // Paper end
         });
     }
 
diff --git a/src/main/java/com/mojang/datafixers/types/Type.java b/src/main/java/com/mojang/datafixers/types/Type.java
index a80e3fee91..2d5bae7a37 100644
--- a/src/main/java/com/mojang/datafixers/types/Type.java
+++ b/src/main/java/com/mojang/datafixers/types/Type.java
@@ -27,8 +27,10 @@ import javax.annotation.Nullable;
 import java.util.Map;
 import java.util.Objects;
 import java.util.Optional;
+import java.util.concurrent.CompletableFuture;
 
 public abstract class Type<A> implements App<Type.Mu, A> {
+    private static final Map<Triple<Type<?>, TypeRewriteRule, PointFreeRule>, CompletableFuture<Optional<? extends RewriteResult<?, ?>>>> PENDING_REWRITE_CACHE = Maps.newConcurrentMap();
     private static final Map<Triple<Type<?>, TypeRewriteRule, PointFreeRule>, Optional<? extends RewriteResult<?, ?>>> REWRITE_CACHE = Maps.newConcurrentMap();
 
     public static class Mu implements K1 {}
@@ -155,11 +157,34 @@ public abstract class Type<A> implements App<Type.Mu, A> {
     @SuppressWarnings("unchecked")
     public Optional<RewriteResult<A, ?>> rewrite(final TypeRewriteRule rule, final PointFreeRule fRule) {
         final Triple<Type<?>, TypeRewriteRule, PointFreeRule> key = Triple.of(this, rule, fRule);
-        if (!REWRITE_CACHE.containsKey(key)) {
-            final Optional<? extends RewriteResult<?, ?>> result = rule.rewrite(this).flatMap(r -> r.view().rewrite(fRule).map(view -> RewriteResult.create(view, r.recData())));
+        // Paper start - concurrency and performance boost - this code under contention would generate multiple rewrites
+        // rewrite this to use a CompletableFuture for pending rewrites. We can not use computeIfAbsent because this is
+        // a recursive call that will block server startup during the Bootstrap phrase thats trying to precache these rewrites
+        Optional<? extends RewriteResult<?, ?>> rewrite = REWRITE_CACHE.get(key);
+        //noinspection OptionalAssignedToNull
+        if (rewrite != null) {
+            return (Optional<RewriteResult<A, ?>>) rewrite;
+        }
+        CompletableFuture<Optional<? extends RewriteResult<?, ?>>> pending;
+        boolean needsCreate;
+        synchronized (PENDING_REWRITE_CACHE) {
+            pending = PENDING_REWRITE_CACHE.get(key);
+            needsCreate = pending == null;
+            if (pending == null) {
+                pending = new CompletableFuture<>();
+                PENDING_REWRITE_CACHE.put(key, pending);
+            }
+        }
+        if (needsCreate) {
+            Optional<RewriteResult<A, ?>> result = rule.rewrite(this).flatMap(r -> r.view().rewrite(fRule).map(view -> RewriteResult.create(view, r.recData())));
             REWRITE_CACHE.put(key, result);
+            pending.complete(result);
+            PENDING_REWRITE_CACHE.remove(key);
+            return result;
+        } else {
+            return (Optional<RewriteResult<A, ?>>) pending.join();
         }
-        return (Optional<RewriteResult<A, ?>>) REWRITE_CACHE.get(key);
+        // Paper end
     }
 
     public <FT, FR> Type<?> getSetType(final OpticFinder<FT> optic, final Type<FR> newType) {
diff --git a/src/main/java/com/mojang/datafixers/types/families/RecursiveTypeFamily.java b/src/main/java/com/mojang/datafixers/types/families/RecursiveTypeFamily.java
index 4a1f906837..93c2f565fd 100644
--- a/src/main/java/com/mojang/datafixers/types/families/RecursiveTypeFamily.java
+++ b/src/main/java/com/mojang/datafixers/types/families/RecursiveTypeFamily.java
@@ -32,7 +32,7 @@ public final class RecursiveTypeFamily implements TypeFamily {
     private final TypeTemplate template;
     private final int size;
 
-    private final Int2ObjectMap<RecursivePoint.RecursivePointType<?>> types = new Int2ObjectOpenHashMap<>();
+    private final Int2ObjectMap<RecursivePoint.RecursivePointType<?>> types = it.unimi.dsi.fastutil.ints.Int2ObjectMaps.synchronize(new Int2ObjectOpenHashMap<>()); // Paper
     private final int hashCode;
 
     public RecursiveTypeFamily(final String name, final TypeTemplate template) {
diff --git a/src/main/java/com/mojang/datafixers/types/templates/Tag.java b/src/main/java/com/mojang/datafixers/types/templates/Tag.java
index ece3fb5f88..396637bbd1 100644
--- a/src/main/java/com/mojang/datafixers/types/templates/Tag.java
+++ b/src/main/java/com/mojang/datafixers/types/templates/Tag.java
@@ -173,8 +173,10 @@ public final class Tag implements TypeTemplate {
         public <T> Pair<T, Optional<A>> read(final DynamicOps<T> ops, final T input) {
             final Optional<Map<T, T>> map = ops.getMapValues(input);
             final T nameObject = ops.createString(name);
-            if (map.isPresent() && map.get().containsKey(nameObject)) {
-                final T elementValue = map.get().get(nameObject);
+            // Paper start - performance - don't use containsKey
+            final T elementValue;
+            if (map.isPresent() && (elementValue = map.get().get(nameObject)) != null) {
+                // Paper end
                 final Optional<A> value = element.read(ops, elementValue).getSecond();
                 if (value.isPresent()) {
                     return Pair.of(ops.createMap(map.get().entrySet().stream().filter(e -> !Objects.equals(e.getKey(), nameObject)).collect(Collectors.toMap(Map.Entry::getKey, Map.Entry::getValue))), value);
diff --git a/src/main/java/com/mojang/datafixers/types/templates/TaggedChoice.java b/src/main/java/com/mojang/datafixers/types/templates/TaggedChoice.java
index e6dd31233a..77d64362b1 100644
--- a/src/main/java/com/mojang/datafixers/types/templates/TaggedChoice.java
+++ b/src/main/java/com/mojang/datafixers/types/templates/TaggedChoice.java
@@ -187,17 +187,25 @@ public final class TaggedChoice<K> implements TypeTemplate {
             if (values.isPresent()) {
                 final Map<T, T> map = values.get();
                 final T nameObject = ops.createString(name);
-                if (map.containsKey(nameObject)) {
-                    final Optional<K> key = keyType.read(ops, map.get(nameObject)).getSecond();
-                    if (!key.isPresent() || !types.containsKey(key.get())) {
+                // Paper start - performance - don't use containsKey
+                T mapValue = map.get(nameObject);
+                if (mapValue != null) {
+                    final Optional<K> key = keyType.read(ops, mapValue).getSecond();
+                    // also skip containsKey here
+                    //noinspection OptionalIsPresent
+                    K keyValue = key.isPresent() ? key.get() : null;
+                    Type<?> type = keyValue != null ? types.get(keyValue) : null;
+                    if (type == null) {
                         if (DataFixerUpper.ERRORS_ARE_FATAL) {
-                            throw new IllegalArgumentException("Unsupported key: " + key.get() + " in " + this);
+                            throw new IllegalArgumentException("Unsupported key: " + keyValue + " in " + this);
                         } else {
-                            LOGGER.warn("Unsupported key: {} in {}", key.get(), this);
+                            LOGGER.warn("Unsupported key: {} in {}", keyValue, this);
                             return Pair.of(input, Optional.empty());
                         }
                     }
-                    return types.get(key.get()).read(ops, input).mapSecond(vo -> vo.map(v -> Pair.of(key.get(), v)));
+
+                    return type.read(ops, input).mapSecond(vo -> vo.map(v -> Pair.of(keyValue, v)));
+                    // Paper end
                 }
             }
             return Pair.of(input, Optional.empty());
@@ -205,12 +213,14 @@ public final class TaggedChoice<K> implements TypeTemplate {
 
         @Override
         public <T> T write(final DynamicOps<T> ops, final T rest, final Pair<K, ?> value) {
-            if (!types.containsKey(value.getFirst())) {
+            // Paper start - performance - don't use containsKey
+            final Type<?> type = types.get(value.getFirst());
+            if (type == null) {
                 // TODO: better error handling?
                 // TODO: See todo in read method
                 throw new IllegalArgumentException("Unsupported key: " + value.getFirst() + " in " + this);
             }
-            final Type<?> type = types.get(value.getFirst());
+            // Paper end
             return capWrite(ops, type, value.getFirst(), value.getSecond(), rest);
         }
 
-- 
2.19.0