Add ReactorResourceFactory

Issue: SPR-16963

Author: rstoyanchev

Diff for: spring-web/src/main/java/org/springframework/http/client/reactive/ReactorClientHttpConnector.java

@@ -26,6 +26,9 @@
 import reactor.netty.http.client.HttpClient;
 import reactor.netty.http.client.HttpClientRequest;
 import reactor.netty.http.client.HttpClientResponse;
+import reactor.netty.resources.ConnectionProvider;
+import reactor.netty.resources.LoopResources;
+import reactor.netty.tcp.TcpClient;
 
 import org.springframework.http.HttpMethod;
 import org.springframework.util.Assert;
@@ -39,21 +42,53 @@
  */
 public class ReactorClientHttpConnector implements ClientHttpConnector {
 
+	private final static Function<HttpClient, HttpClient> defaultInitializer = HttpClient::compress;
+
+
 	private final HttpClient httpClient;
 
 
 	/**
-	 * Create a Reactor Netty {@link ClientHttpConnector}
-	 * with default configuration and HTTP compression support enabled.
+	 * Default constructor that initializes an {@link HttpClient} with:
+	 * <pre class="code">
+	 * HttpClient.create().compress()
+	 * </pre>
 	 */
 	public ReactorClientHttpConnector() {
-		this.httpClient = HttpClient.create().compress();
+		this.httpClient = defaultInitializer.apply(HttpClient.create());
+	}
+
+	/**
+	 * Constructor with externally managed Reactor Netty resources, including
+	 * {@link LoopResources} for event loop threads, and {@link ConnectionProvider}
+	 * for the connection pool.
+	 * <p>This constructor should be used only when you don't want the client
+	 * to participate in the Reactor Netty global resources. By default the
+	 * client participates in the Reactor Netty global resources held in
+	 * {@link reactor.netty.http.HttpResources}, which is recommended since
+	 * fixed, shared resources are favored for event loop concurrency. However,
+	 * consider declaring a {@link ReactorResourceFactory} bean with
+	 * {@code globaResources=true} in order to ensure the Reactor Netty global
+	 * resources are shut down when the Spring ApplicationContext is closed.
+	 * @param factory the resource factory to obtain the resources from
+	 * @param mapper a mapper for further initialization of the created client
+	 * @since 5.1
+	 */
+	public ReactorClientHttpConnector(ReactorResourceFactory factory, Function<HttpClient, HttpClient> mapper) {
+		this.httpClient = defaultInitializer.andThen(mapper).apply(initHttpClient(factory));
+	}
+
+	private static HttpClient initHttpClient(ReactorResourceFactory resourceFactory) {
+		ConnectionProvider provider = resourceFactory.getConnectionProvider();
+		LoopResources resources = resourceFactory.getLoopResources();
+		Assert.notNull(provider, "No ConnectionProvider: is ReactorResourceFactory not initialized yet?");
+		Assert.notNull(resources, "No LoopResources: is ReactorResourceFactory not initialized yet?");
+		return HttpClient.create(provider).tcpConfiguration(tcpClient -> tcpClient.runOn(resources)).compress();
 	}
 
 	/**
-	 * Create a Reactor Netty {@link ClientHttpConnector} with a fully
-	 * configured {@code HttpClient}.
-	 * @param httpClient the client instance to use
+	 * Constructor with a pre-configured {@code HttpClient} instance.
+	 * @param httpClient the client to use
 	 * @since 5.1
 	 */
 	public ReactorClientHttpConnector(HttpClient httpClient) {

Diff for: spring-web/src/main/java/org/springframework/http/client/reactive/ReactorResourceFactory.java

@@ -0,0 +1,153 @@
+/*
+ * Copyright 2002-2018 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.springframework.http.client.reactive;
+
+import reactor.netty.http.HttpResources;
+import reactor.netty.resources.ConnectionProvider;
+import reactor.netty.resources.LoopResources;
+
+import org.springframework.beans.factory.DisposableBean;
+import org.springframework.beans.factory.InitializingBean;
+import org.springframework.lang.Nullable;
+import org.springframework.util.Assert;
+
+/**
+ * Factory to manage Reactor Netty resources, i.e. {@link LoopResources} for
+ * event loop threads, and {@link ConnectionProvider} for the connection pool,
+ * within the lifecycle of a Spring {@code ApplicationContext}.
+ *
+ * <p>This factory implements {@link InitializingBean} and {@link DisposableBean}
+ * and is expected typically to be declared as a Spring-managed bean.
+ *
+ * @author Rossen Stoyanchev
+ * @since 5.1
+ */
+public class ReactorResourceFactory implements InitializingBean, DisposableBean {
+
+	private boolean globalResources = true;
+
+	@Nullable
+	private ConnectionProvider connectionProvider;
+
+	@Nullable
+	private LoopResources loopResources;
+
+	private String threadPrefix = "reactor-http";
+
+
+	/**
+	 * Whether to expose and manage the global Reactor Netty resources from the
+	 * {@link HttpResources} holder.
+	 * <p>Default is "true" in which case this factory helps to configure and
+	 * shut down the global Reactor Netty resources within the lifecycle of a
+	 * Spring {@code ApplicationContext}.
+	 * <p>If set to "false" then the factory creates and manages its own
+	 * {@link LoopResources} and {@link ConnectionProvider}, independent of the
+	 * global ones in the {@link HttpResources} holder.
+	 * @param globalResources whether to expose and manage the global resources
+	 */
+	public void setGlobalResources(boolean globalResources) {
+		this.globalResources = globalResources;
+	}
+
+	/**
+	 * Configure the {@link ConnectionProvider} to use.
+	 * <p>By default, initialized with {@link ConnectionProvider#elastic(String)}.
+	 * @param connectionProvider the connection provider to use
+	 */
+	public void setConnectionProvider(@Nullable ConnectionProvider connectionProvider) {
+		this.connectionProvider = connectionProvider;
+	}
+
+	/**
+	 * Configure the {@link LoopResources} to use.
+	 * <p>By default, initialized with {@link LoopResources#create(String)}.
+	 * @param loopResources the loop resources to use
+	 */
+	public void setLoopResources(@Nullable LoopResources loopResources) {
+		this.loopResources = loopResources;
+	}
+
+	/**
+	 * Configure the thread prefix to initialize {@link LoopResources} with. This
+	 * is used only when a {@link LoopResources} instance isn't
+	 * {@link #setLoopResources(LoopResources) provided}.
+	 * <p>By default set to "reactor-http".
+	 * @param threadPrefix the thread prefix to use
+	 */
+	public void setThreadPrefix(String threadPrefix) {
+		Assert.notNull(threadPrefix, "Thread prefix is required");
+		this.threadPrefix = threadPrefix;
+	}
+
+
+	/**
+	 * Whether this factory exposes the global
+	 * {@link reactor.netty.http.HttpResources HttpResources} holder.
+	 */
+	public boolean isGlobalResources() {
+		return this.globalResources;
+	}
+
+	/**
+	 * Return the configured {@link ConnectionProvider}.
+	 */
+	@Nullable
+	public ConnectionProvider getConnectionProvider() {
+		return this.connectionProvider;
+	}
+
+	/**
+	 * Return the configured {@link LoopResources}.
+	 */
+	@Nullable
+	public LoopResources getLoopResources() {
+		return this.loopResources;
+	}
+
+	/**
+	 * Return the configured prefix for event loop threads.
+	 */
+	public String getThreadPrefix() {
+		return this.threadPrefix;
+	}
+
+
+	@Override
+	public void afterPropertiesSet() throws Exception {
+		if (this.loopResources == null) {
+			this.loopResources = LoopResources.create(this.threadPrefix);
+		}
+		if (this.connectionProvider == null) {
+			this.connectionProvider = ConnectionProvider.elastic("http");
+		}
+		if (this.globalResources) {
+			HttpResources.set(this.loopResources);
+			HttpResources.set(this.connectionProvider);
+		}
+	}
+
+	@Override
+	public void destroy() {
+
+		Assert.notNull(this.connectionProvider, "No ConnectionProvider");
+		this.connectionProvider.dispose();
+
+		Assert.notNull(this.loopResources, "No LoopResources");
+		this.loopResources.dispose();
+	}
+
+}