Defer accessing loop resources until web server start

Closes gh-37209

Author: wilkinsona

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/web/embedded/netty/NettyReactiveWebServerFactory.java

@@ -27,7 +27,6 @@
 
 import reactor.netty.http.HttpProtocol;
 import reactor.netty.http.server.HttpServer;
-import reactor.netty.resources.LoopResources;
 
 import org.springframework.boot.web.reactive.server.AbstractReactiveWebServerFactory;
 import org.springframework.boot.web.reactive.server.ReactiveWebServerFactory;
@@ -78,7 +77,7 @@ public WebServer getWebServer(HttpHandler httpHandler) {
 
 	NettyWebServer createNettyWebServer(HttpServer httpServer, ReactorHttpHandlerAdapter handlerAdapter,
 			Duration lifecycleTimeout, Shutdown shutdown) {
-		return new NettyWebServer(httpServer, handlerAdapter, lifecycleTimeout, shutdown);
+		return new NettyWebServer(httpServer, handlerAdapter, lifecycleTimeout, shutdown, this.resourceFactory);
 	}
 
 	/**
@@ -158,15 +157,7 @@ public Shutdown getShutdown() {
 	}
 
 	private HttpServer createHttpServer() {
-		HttpServer server = HttpServer.create();
-		if (this.resourceFactory != null) {
-			LoopResources resources = this.resourceFactory.getLoopResources();
-			Assert.notNull(resources, "No LoopResources: is ReactorResourceFactory not initialized yet?");
-			server = server.runOn(resources).bindAddress(this::getListenAddress);
-		}
-		else {
-			server = server.bindAddress(this::getListenAddress);
-		}
+		HttpServer server = HttpServer.create().bindAddress(this::getListenAddress);
 		if (Ssl.isEnabled(getSsl())) {
 			server = customizeSslConfiguration(server);
 		}

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/web/embedded/netty/NettyWebServer.java

@@ -35,13 +35,15 @@
 import reactor.netty.http.server.HttpServerRequest;
 import reactor.netty.http.server.HttpServerResponse;
 import reactor.netty.http.server.HttpServerRoutes;
+import reactor.netty.resources.LoopResources;
 
 import org.springframework.boot.web.server.GracefulShutdownCallback;
 import org.springframework.boot.web.server.GracefulShutdownResult;
 import org.springframework.boot.web.server.PortInUseException;
 import org.springframework.boot.web.server.Shutdown;
 import org.springframework.boot.web.server.WebServer;
 import org.springframework.boot.web.server.WebServerException;
+import org.springframework.http.client.reactive.ReactorResourceFactory;
 import org.springframework.http.server.reactive.ReactorHttpHandlerAdapter;
 import org.springframework.util.Assert;
 
@@ -74,19 +76,48 @@ public class NettyWebServer implements WebServer {
 
 	private final GracefulShutdown gracefulShutdown;
 
+	private final ReactorResourceFactory resourceFactory;
+
 	private List<NettyRouteProvider> routeProviders = Collections.emptyList();
 
 	private volatile DisposableServer disposableServer;
 
+	/**
+	 * Creates a new {@code NettyWebServer} instance.
+	 * @param httpServer the HTTP server
+	 * @param handlerAdapter the handler adapter
+	 * @param lifecycleTimeout the lifecycle timeout, may be {@code null}
+	 * @param shutdown the shutdown, may be {@code null}
+	 * @deprecated since 3.2.0 for removal in 3.4.0 in favor of
+	 * {@link #NettyWebServer(HttpServer, ReactorHttpHandlerAdapter, Duration, Shutdown, ReactorResourceFactory)}
+	 */
+	@Deprecated(since = "3.2.0", forRemoval = true)
 	public NettyWebServer(HttpServer httpServer, ReactorHttpHandlerAdapter handlerAdapter, Duration lifecycleTimeout,
 			Shutdown shutdown) {
+		this(httpServer, handlerAdapter, lifecycleTimeout, shutdown, null);
+	}
+
+	/**
+	 * Creates a new {@code NettyWebServer} instance.
+	 * @param httpServer the HTTP server
+	 * @param handlerAdapter the handler adapter
+	 * @param lifecycleTimeout the lifecycle timeout, may be {@code null}
+	 * @param shutdown the shutdown, may be {@code null}
+	 * @param resourceFactory the factory for the server's {@link LoopResources loop
+	 * resources}, may be {@code null}
+	 * @since 3.2.0
+	 * {@link #NettyWebServer(HttpServer, ReactorHttpHandlerAdapter, Duration, Shutdown, ReactorResourceFactory)}
+	 */
+	public NettyWebServer(HttpServer httpServer, ReactorHttpHandlerAdapter handlerAdapter, Duration lifecycleTimeout,
+			Shutdown shutdown, ReactorResourceFactory resourceFactory) {
 		Assert.notNull(httpServer, "HttpServer must not be null");
 		Assert.notNull(handlerAdapter, "HandlerAdapter must not be null");
 		this.lifecycleTimeout = lifecycleTimeout;
 		this.handler = handlerAdapter;
 		this.httpServer = httpServer.channelGroup(new DefaultChannelGroup(new DefaultEventExecutor()));
 		this.gracefulShutdown = (shutdown == Shutdown.GRACEFUL) ? new GracefulShutdown(() -> this.disposableServer)
 				: null;
+		this.resourceFactory = resourceFactory;
 	}
 
 	public void setRouteProviders(List<NettyRouteProvider> routeProviders) {
@@ -143,6 +174,11 @@ DisposableServer startHttpServer() {
 		else {
 			server = server.route(this::applyRouteProviders);
 		}
+		if (this.resourceFactory != null) {
+			LoopResources resources = this.resourceFactory.getLoopResources();
+			Assert.notNull(resources, "No LoopResources: is ReactorResourceFactory not initialized yet?");
+			server = server.runOn(resources);
+		}
 		if (this.lifecycleTimeout != null) {
 			return server.bindNow(this.lifecycleTimeout);
 		}

spring-boot-project/spring-boot/src/test/java/org/springframework/boot/web/embedded/netty/NettyReactiveWebServerFactoryTests.java

@@ -41,12 +41,14 @@
 import org.springframework.boot.web.server.Ssl;
 import org.springframework.http.MediaType;
 import org.springframework.http.client.reactive.ReactorClientHttpConnector;
+import org.springframework.http.client.reactive.ReactorResourceFactory;
 import org.springframework.http.server.reactive.ReactorHttpHandlerAdapter;
 import org.springframework.web.reactive.function.BodyInserters;
 import org.springframework.web.reactive.function.client.WebClient;
 
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.assertj.core.api.Assertions.assertThatExceptionOfType;
+import static org.assertj.core.api.Assertions.assertThatNoException;
 import static org.mockito.ArgumentMatchers.any;
 import static org.mockito.BDDMockito.given;
 import static org.mockito.Mockito.inOrder;
@@ -80,6 +82,23 @@ void getPortWhenDisposableServerPortOperationIsUnsupportedReturnsMinusOne() {
 		assertThat(this.webServer.getPort()).isEqualTo(-1);
 	}
 
+	@Test
+	void resourceFactoryAndWebServerLifecycle() {
+		NettyReactiveWebServerFactory factory = getFactory();
+		factory.setPort(0);
+		ReactorResourceFactory resourceFactory = new ReactorResourceFactory();
+		factory.setResourceFactory(resourceFactory);
+		this.webServer = factory.getWebServer(new EchoHandler());
+		assertThatNoException().isThrownBy(() -> {
+			resourceFactory.start();
+			this.webServer.start();
+			this.webServer.stop();
+			resourceFactory.stop();
+			resourceFactory.start();
+			this.webServer.start();
+		});
+	}
+
 	private void portMatchesRequirement(PortInUseException exception) {
 		assertThat(exception.getPort()).isEqualTo(this.webServer.getPort());
 	}
@@ -199,7 +218,7 @@ static class NoPortNettyWebServer extends NettyWebServer {
 
 		NoPortNettyWebServer(HttpServer httpServer, ReactorHttpHandlerAdapter handlerAdapter, Duration lifecycleTimeout,
 				Shutdown shutdown) {
-			super(httpServer, handlerAdapter, lifecycleTimeout, shutdown);
+			super(httpServer, handlerAdapter, lifecycleTimeout, shutdown, null);
 		}
 
 		@Override