Ensure correct initial capacity is used for the map (#2739)

reactor-netty-core/src/main/java/reactor/netty/internal/util/MapUtils.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2022 VMware, Inc. or its affiliates, All Rights Reserved.
+ * Copyright (c) 2022-2023 VMware, Inc. or its affiliates, All Rights Reserved.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -19,8 +19,7 @@
 import java.util.function.Function;
 
 /**
- * It's a temporary workaround for Java 8 specific performance issue JDK-8161372
- * and this class should be removed once the Java 8 support is dropped.
+ * This class contains temporary workarounds for Java 8 {@link Map} issues.
  * <p><strong>Note:</strong> This utility class is for internal use only. It can be removed at any time.
  *
  * @author zimatars
@@ -29,6 +28,24 @@
 public final class MapUtils {
 
 	/**
+	 * This is a temporary workaround for Java 8 issue https://bugs.openjdk.org/browse/JDK-8186958. Fix is available
+	 * in Java 19.
+	 * <p>
+	 * Calculate the initial capacity for the {@link Map} from the expected size and the default load factor
+	 * for the {@link Map} (0.75).
+	 *
+	 * @param expectedSize the expected size
+	 * @return the initial capacity for the {@link Map}
+	 * @since 1.0.31
+	 */
+	public static int calculateInitialCapacity(int expectedSize) {
+		return (int) Math.ceil(expectedSize / 0.75);
+	}
+
+	/**
+	 * This is a temporary workaround for Java 8 specific performance issue https://bugs.openjdk.org/browse/JDK-8161372.
+	 * Fix is available in Java 9.
+	 * <p>
 	 * ConcurrentHashMap.computeIfAbsent(k,v) locks when k is present.
 	 * Add pre-screen before locking inside computeIfAbsent.
 	 * <p><strong>Note:</strong> This utility is not for a general purpose usage.

reactor-netty-core/src/main/java/reactor/netty/tcp/TcpServerBind.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2017-2021 VMware, Inc. or its affiliates, All Rights Reserved.
+ * Copyright (c) 2017-2023 VMware, Inc. or its affiliates, All Rights Reserved.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -18,6 +18,7 @@
 import io.netty.channel.ChannelOption;
 import reactor.core.publisher.Mono;
 import reactor.netty.DisposableServer;
+import reactor.netty.internal.util.MapUtils;
 
 import java.net.InetSocketAddress;
 import java.util.Collections;
@@ -37,7 +38,7 @@ final class TcpServerBind extends TcpServer {
 	final TcpServerConfig config;
 
 	TcpServerBind() {
-		Map<ChannelOption<?>, Boolean> childOptions = new HashMap<>(2);
+		Map<ChannelOption<?>, Boolean> childOptions = new HashMap<>(MapUtils.calculateInitialCapacity(2));
 		childOptions.put(ChannelOption.AUTO_READ, false);
 		childOptions.put(ChannelOption.TCP_NODELAY, true);
 		this.config = new TcpServerConfig(

reactor-netty-core/src/main/java/reactor/netty/transport/ServerTransport.java

@@ -537,7 +537,7 @@ public void disposeNow(Duration timeout) {
 			Mono<Void> terminateSignals = Mono.empty();
 			if (config.channelGroup != null && config.channelGroup.size() > 0) {
 				HashMap<Channel, List<Mono<Void>>> channelsToMono =
-						new HashMap<>((int) Math.ceil(config.channelGroup.size() / 0.75));
+						new HashMap<>(MapUtils.calculateInitialCapacity(config.channelGroup.size()));
 				// Wait for the running requests to finish
 				for (Channel channel : config.channelGroup) {
 					Channel parent = channel.parent();

reactor-netty-core/src/main/java/reactor/netty/transport/TransportConfig.java

@@ -39,6 +39,7 @@
 import reactor.netty.NettyPipeline;
 import reactor.netty.channel.ChannelMetricsRecorder;
 import reactor.netty.channel.ChannelOperations;
+import reactor.netty.internal.util.MapUtils;
 import reactor.netty.resources.LoopResources;
 import reactor.util.Logger;
 import reactor.util.Loggers;
@@ -351,7 +352,7 @@ protected static <K, V> Map<K, V> updateMap(Map<K, V> parentMap, Object key, @Nu
 			return value == null ? parentMap : Collections.singletonMap((K) key, (V) value);
 		}
 		else {
-			Map<K, V> attrs = new HashMap<>(parentMap.size() + 1);
+			Map<K, V> attrs = new HashMap<>(MapUtils.calculateInitialCapacity(parentMap.size() + 1));
 			attrs.putAll(parentMap);
 			if (value == null) {
 				attrs.remove(key);

reactor-netty-http/src/main/java/reactor/netty/http/server/HttpPredicate.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2011-2021 VMware, Inc. or its affiliates, All Rights Reserved.
+ * Copyright (c) 2011-2023 VMware, Inc. or its affiliates, All Rights Reserved.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -26,6 +26,7 @@
 
 import io.netty.handler.codec.http.HttpMethod;
 import io.netty.handler.codec.http.HttpVersion;
+import reactor.netty.internal.util.MapUtils;
 import reactor.util.annotation.Nullable;
 
 import static java.util.Objects.requireNonNull;
@@ -344,7 +345,7 @@ public boolean matches(String uri) {
 		 * @return the path parameters from the uri. Never {@code null}.
 		 */
 		final Map<String, String> match(String uri) {
-			Map<String, String> pathParameters = new HashMap<>(pathVariables.size());
+			Map<String, String> pathParameters = new HashMap<>(MapUtils.calculateInitialCapacity(pathVariables.size()));
 
 			Matcher m = matcher(uri);
 			if (m.matches()) {

reactor-netty-http/src/main/java/reactor/netty/http/server/HttpServerBind.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2017-2021 VMware, Inc. or its affiliates, All Rights Reserved.
+ * Copyright (c) 2017-2023 VMware, Inc. or its affiliates, All Rights Reserved.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -19,6 +19,7 @@
 import io.netty.util.AttributeKey;
 import reactor.core.publisher.Mono;
 import reactor.netty.DisposableServer;
+import reactor.netty.internal.util.MapUtils;
 import reactor.netty.tcp.SslProvider;
 import reactor.netty.tcp.TcpServerConfig;
 
@@ -41,7 +42,7 @@ final class HttpServerBind extends HttpServer {
 	final HttpServerConfig config;
 
 	HttpServerBind() {
-		Map<ChannelOption<?>, Boolean> childOptions = new HashMap<>(2);
+		Map<ChannelOption<?>, Boolean> childOptions = new HashMap<>(MapUtils.calculateInitialCapacity(2));
 		childOptions.put(ChannelOption.AUTO_READ, false);
 		childOptions.put(ChannelOption.TCP_NODELAY, true);
 		this.config = new HttpServerConfig(