Ensure client response is drained with onStatus hook

Issue: SPR-17473

spring-core/src/test/java/org/springframework/core/io/buffer/AbstractDataBufferAllocatingTestCase.java

@@ -17,6 +17,8 @@
 package org.springframework.core.io.buffer;
 
 import java.nio.charset.StandardCharsets;
+import java.time.Duration;
+import java.time.Instant;
 import java.util.Arrays;
 import java.util.List;
 import java.util.function.Consumer;
@@ -37,7 +39,11 @@ import org.springframework.core.io.buffer.support.DataBufferTestUtils;
 import static org.junit.Assert.*;
 
 /**
+ * Base class for tests that read or write data buffers with a rule to check
+ * that allocated buffers have been released.
+ *
  * @author Arjen Poutsma
+ * @author Rossen Stoyanchev
  */
 @RunWith(Parameterized.class)
 public abstract class AbstractDataBufferAllocatingTestCase {
@@ -62,6 +68,7 @@ public abstract class AbstractDataBufferAllocatingTestCase {
 	@Rule
 	public final Verifier leakDetector = new LeakDetector();
 
+
 	protected DataBuffer createDataBuffer(int capacity) {
 		return this.bufferFactory.allocateBuffer(capacity);
 	}
@@ -93,30 +100,45 @@ public abstract class AbstractDataBufferAllocatingTestCase {
 		};
 	}
 
+	/**
+	 * Wait until allocations are at 0, or the given duration elapses.
+	 */
+	protected void waitForDataBufferRelease(Duration duration) throws InterruptedException {
+		Instant start = Instant.now();
+		while (Instant.now().isBefore(start.plus(duration))) {
+			try {
+				verifyAllocations();
+				break;
+			}
+			catch (AssertionError ex) {
+				// ignore;
+			}
+			Thread.sleep(50);
+		}
+	}
 
-	private class LeakDetector extends Verifier {
-
-		@Override
-		protected void verify() throws Throwable {
-			if (bufferFactory instanceof NettyDataBufferFactory) {
-				ByteBufAllocator byteBufAllocator =
-						((NettyDataBufferFactory) bufferFactory).getByteBufAllocator();
-				if (byteBufAllocator instanceof PooledByteBufAllocator) {
-					PooledByteBufAllocator pooledByteBufAllocator =
-							(PooledByteBufAllocator) byteBufAllocator;
-					PooledByteBufAllocatorMetric metric = pooledByteBufAllocator.metric();
-					long allocations = calculateAllocations(metric.directArenas()) +
-							calculateAllocations(metric.heapArenas());
-					assertTrue("ByteBuf leak detected: " + allocations +
-							" allocations were not released", allocations == 0);
-				}
+	private void verifyAllocations() {
+		if (this.bufferFactory instanceof NettyDataBufferFactory) {
+			ByteBufAllocator allocator = ((NettyDataBufferFactory) this.bufferFactory).getByteBufAllocator();
+			if (allocator instanceof PooledByteBufAllocator) {
+				PooledByteBufAllocatorMetric metric = ((PooledByteBufAllocator) allocator).metric();
+				long total = getAllocations(metric.directArenas()) + getAllocations(metric.heapArenas());
+				assertEquals("ByteBuf Leak: " + total + " unreleased allocations", 0, total);
 			}
 		}
+	}
 
-		private long calculateAllocations(List<PoolArenaMetric> metrics) {
-			return metrics.stream().mapToLong(PoolArenaMetric::numActiveAllocations).sum();
+	private static long getAllocations(List<PoolArenaMetric> metrics) {
+		return metrics.stream().mapToLong(PoolArenaMetric::numActiveAllocations).sum();
+	}
+
+
+	protected class LeakDetector extends Verifier {
+
+		@Override
+		public void verify() {
+			AbstractDataBufferAllocatingTestCase.this.verifyAllocations();
 		}
-
 	}
 
 }

spring-web/src/main/java/org/springframework/http/client/reactive/ReactorClientHttpResponse.java

@@ -17,6 +17,7 @@
 package org.springframework.http.client.reactive;
 
 import java.util.Collection;
+import java.util.concurrent.atomic.AtomicBoolean;
 
 import io.netty.buffer.ByteBufAllocator;
 import reactor.core.publisher.Flux;
@@ -28,6 +29,7 @@ import org.springframework.core.io.buffer.NettyDataBufferFactory;
 import org.springframework.http.HttpHeaders;
 import org.springframework.http.HttpStatus;
 import org.springframework.http.ResponseCookie;
+import org.springframework.util.Assert;
 import org.springframework.util.CollectionUtils;
 import org.springframework.util.LinkedMultiValueMap;
 import org.springframework.util.MultiValueMap;
@@ -47,6 +49,8 @@ class ReactorClientHttpResponse implements ClientHttpResponse {
 
 	private final NettyInbound inbound;
 
+	private final AtomicBoolean bodyConsumed = new AtomicBoolean();
+
 
 	public ReactorClientHttpResponse(HttpClientResponse response, NettyInbound inbound, ByteBufAllocator alloc) {
 		this.response = response;
@@ -58,6 +62,10 @@ class ReactorClientHttpResponse implements ClientHttpResponse {
 	@Override
 	public Flux<DataBuffer> getBody() {
 		return this.inbound.receive()
+				.doOnSubscribe(s ->
+						// See https://github.com/reactor/reactor-netty/issues/503
+						Assert.state(this.bodyConsumed.compareAndSet(false, true),
+								"The client response body can only be consumed once."))
 				.map(byteBuf -> {
 					byteBuf.retain();
 					return this.bufferFactory.wrap(byteBuf);

spring-webflux/src/main/java/org/springframework/web/reactive/function/client/DefaultWebClient.java

@@ -436,19 +436,30 @@ class DefaultWebClient implements WebClient {
 
 		private <T extends Publisher<?>> T bodyToPublisher(ClientResponse response,
 				T bodyPublisher, Function<Mono<? extends Throwable>, T> errorFunction) {
+
 			if (HttpStatus.resolve(response.rawStatusCode()) != null) {
-				return this.statusHandlers.stream()
-						.filter(statusHandler -> statusHandler.test(response.statusCode()))
-						.findFirst()
-						.map(statusHandler -> statusHandler.apply(response))
-						.map(errorFunction::apply)
-						.orElse(bodyPublisher);
+				for (StatusHandler handler : this.statusHandlers) {
+					if (handler.test(response.statusCode())) {
+						Mono<? extends Throwable> exMono = handler.apply(response);
+						exMono = exMono.flatMap(ex -> drainBody(response, ex));
+						exMono = exMono.onErrorResume(ex -> drainBody(response, ex));
+						return errorFunction.apply(exMono);
+					}
+				}
+				return bodyPublisher;
 			}
 			else {
 				return errorFunction.apply(createResponseException(response));
 			}
 		}
 
+		@SuppressWarnings("unchecked")
+		private <T> Mono<T> drainBody(ClientResponse response, Throwable ex) {
+			// Ensure the body is drained, even if the StatusHandler didn't consume it,
+			// but ignore errors in case it did consume it.
+			return (Mono<T>) response.bodyToMono(Void.class).onErrorMap(ex2 -> ex).thenReturn(ex);
+		}
+
 		private static Mono<WebClientResponseException> createResponseException(ClientResponse response) {
 			return DataBufferUtils.join(response.body(BodyExtractors.toDataBuffers()))
 					.map(dataBuffer -> {

spring-webflux/src/main/java/org/springframework/web/reactive/function/client/WebClient.java

@@ -595,6 +595,9 @@ public interface WebClient {
 		 * {@link WebClientResponseException} when the response status code is 4xx or 5xx.
 		 * @param statusPredicate a predicate that indicates whether {@code exceptionFunction}
 		 * applies
+		 * <p><strong>NOTE:</strong> if the response is expected to have content,
+		 * the exceptionFunction should consume it. If not, the content will be
+		 * automatically drained to ensure resources are released.
 		 * @param exceptionFunction the function that returns the exception
 		 * @return this builder
 		 */

spring-webflux/src/test/java/org/springframework/web/reactive/function/client/WebClientDataBufferAllocatingTests.java

@@ -0,0 +1,151 @@
+/*
+ * 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.web.reactive.function.client;
+
+import java.time.Duration;
+import java.util.function.Function;
+
+import io.netty.buffer.ByteBufAllocator;
+import io.netty.channel.ChannelOption;
+import okhttp3.mockwebserver.MockResponse;
+import okhttp3.mockwebserver.MockWebServer;
+import org.junit.After;
+import org.junit.Before;
+import org.junit.Test;
+import reactor.core.publisher.Mono;
+import reactor.test.StepVerifier;
+
+import org.springframework.core.io.buffer.AbstractDataBufferAllocatingTestCase;
+import org.springframework.core.io.buffer.NettyDataBufferFactory;
+import org.springframework.http.HttpStatus;
+import org.springframework.http.MediaType;
+import org.springframework.http.client.reactive.ReactorClientHttpConnector;
+import org.springframework.http.client.reactive.ReactorResourceFactory;
+
+import static org.junit.Assert.*;
+
+/**
+ * WebClient integration tests focusing on data buffer management.
+ * @author Rossen Stoyanchev
+ */
+public class WebClientDataBufferAllocatingTests extends AbstractDataBufferAllocatingTestCase {
+
+	private static final Duration DELAY = Duration.ofSeconds(5);
+
+
+	private MockWebServer server;
+
+	private WebClient webClient;
+
+	private ReactorResourceFactory factory;
+
+
+	@Before
+	public void setUp() {
+
+		this.factory = new ReactorResourceFactory();
+		this.factory.afterPropertiesSet();
+
+		this.server = new MockWebServer();
+		this.webClient = WebClient
+				.builder()
+				.clientConnector(initConnector())
+				.baseUrl(this.server.url("/").toString())
+				.build();
+	}
+
+	private ReactorClientHttpConnector initConnector() {
+		if (bufferFactory instanceof NettyDataBufferFactory) {
+			ByteBufAllocator allocator = ((NettyDataBufferFactory) bufferFactory).getByteBufAllocator();
+			return new ReactorClientHttpConnector(this.factory, httpClient ->
+					httpClient.tcpConfiguration(tcpClient -> tcpClient.option(ChannelOption.ALLOCATOR, allocator)));
+		}
+		else {
+			return new ReactorClientHttpConnector();
+		}
+	}
+
+	@After
+	public void shutDown() throws InterruptedException {
+		waitForDataBufferRelease(Duration.ofSeconds(2));
+		this.factory.destroy();
+	}
+
+
+
+	@Test
+	public void bodyToMonoVoid() {
+
+		this.server.enqueue(new MockResponse()
+				.setResponseCode(201)
+				.setHeader("Content-Type", "application/json")
+				.setChunkedBody("{\"foo\" : {\"bar\" : \"123\", \"baz\" : \"456\"}}", 5));
+
+		Mono<Void> mono = this.webClient.get()
+				.uri("/json").accept(MediaType.APPLICATION_JSON)
+				.retrieve()
+				.bodyToMono(Void.class);
+
+		StepVerifier.create(mono).expectComplete().verify(Duration.ofSeconds(3));
+		assertEquals(1, this.server.getRequestCount());
+	}
+
+
+	@Test
+	public void onStatusWithBodyNotConsumed() {
+		RuntimeException ex = new RuntimeException("response error");
+		testOnStatus(ex, response -> Mono.just(ex));
+	}
+
+	@Test
+	public void onStatusWithBodyConsumed() {
+		RuntimeException ex = new RuntimeException("response error");
+		testOnStatus(ex, response -> response.bodyToMono(Void.class).thenReturn(ex));
+	}
+
+	@Test // SPR-17473
+	public void onStatusWithMonoErrorAndBodyNotConsumed() {
+		RuntimeException ex = new RuntimeException("response error");
+		testOnStatus(ex, response -> Mono.error(ex));
+	}
+
+	@Test
+	public void onStatusWithMonoErrorAndBodyConsumed() {
+		RuntimeException ex = new RuntimeException("response error");
+		testOnStatus(ex, response -> response.bodyToMono(Void.class).then(Mono.error(ex)));
+	}
+
+	private void testOnStatus(Throwable expected,
+			Function<ClientResponse, Mono<? extends Throwable>> exceptionFunction) {
+
+		HttpStatus errorStatus = HttpStatus.BAD_GATEWAY;
+
+		this.server.enqueue(new MockResponse()
+				.setResponseCode(errorStatus.value())
+				.setHeader("Content-Type", "application/json")
+				.setChunkedBody("{\"error\" : {\"status\" : 502, \"message\" : \"Bad gateway.\"}}", 5));
+
+		Mono<String> mono = this.webClient.get()
+				.uri("/json").accept(MediaType.APPLICATION_JSON)
+				.retrieve()
+				.onStatus(status -> status.equals(errorStatus), exceptionFunction)
+				.bodyToMono(String.class);
+
+		StepVerifier.create(mono).expectErrorSatisfies(actual -> assertSame(expected, actual)).verify(DELAY);
+		assertEquals(1, this.server.getRequestCount());
+	}
+
+}

src/docs/asciidoc/web/webflux-webclient.adoc

@@ -294,6 +294,10 @@ as the following example shows:
 ----
 ====
 
+When `onStatus` is used, if the response is expected to have content, then the `onStatus`
+callback should consume it. If not, the content will be automatically drained to ensure
+resources are released.
+