Correlated WebClient log messages

Issue: SPR-16966

Author: rstoyanchev

spring-web/src/main/java/org/springframework/web/server/ServerWebExchange.java

@@ -222,7 +222,7 @@ default <T> T getAttributeOrDefault(String name, T defaultValue) {
 	 * Return a log message prefix to use to correlate messages for this exchange.
 	 * The prefix is based on the value of the attribute {@link #LOG_ID_ATTRIBUTE}
 	 * along with some extra formatting so that the prefix can be conveniently
-	 * prepended with no further formatting no separatorns required.
+	 * prepended with no further formatting no separators required.
 	 * @return the log message prefix or an empty String if the
 	 * {@link #LOG_ID_ATTRIBUTE} is not set.
 	 * @since 5.1

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

@@ -45,6 +45,16 @@
  */
 public interface ClientRequest {
 
+	/**
+	 * Name of {@link #attributes() attribute} whose value can be used to
+	 * correlate log messages for this request. Use {@link #logPrefix()} to
+	 * obtain a consistently formatted prefix based on this attribute.
+	 * @since 5.1
+	 * @see #logPrefix()
+	 */
+	String LOG_ID_ATTRIBUTE = ClientRequest.class.getName() + ".LOG_ID";
+
+
 	/**
 	 * Return the HTTP method.
 	 */
@@ -90,6 +100,17 @@ default Optional<Object> attribute(String name) {
 	 */
 	Map<String, Object> attributes();
 
+	/**
+	 * Return a log message prefix to use to correlate messages for this request.
+	 * The prefix is based on the value of the attribute {@link #LOG_ID_ATTRIBUTE}
+	 * along with some extra formatting so that the prefix can be conveniently
+	 * prepended with no further formatting no separators required.
+	 * @return the log message prefix or an empty String if the
+	 * {@link #LOG_ID_ATTRIBUTE} is not set.
+	 * @since 5.1
+	 */
+	String logPrefix();
+
 	/**
 	 * Writes this request to the given {@link ClientHttpRequest}.
 	 *

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

@@ -39,6 +39,7 @@
 import org.springframework.util.CollectionUtils;
 import org.springframework.util.LinkedMultiValueMap;
 import org.springframework.util.MultiValueMap;
+import org.springframework.util.ObjectUtils;
 import org.springframework.web.reactive.function.BodyInserter;
 import org.springframework.web.reactive.function.BodyInserters;
 
@@ -181,6 +182,9 @@ private static class BodyInserterRequest implements ClientRequest {
 
 		private final Map<String, Object> attributes;
 
+		private final String logPrefix;
+
+
 		public BodyInserterRequest(HttpMethod method, URI url, HttpHeaders headers,
 				MultiValueMap<String, String> cookies, BodyInserter<?, ? super ClientHttpRequest> body,
 				Map<String, Object> attributes) {
@@ -191,8 +195,12 @@ public BodyInserterRequest(HttpMethod method, URI url, HttpHeaders headers,
 			this.cookies = CollectionUtils.unmodifiableMultiValueMap(cookies);
 			this.body = body;
 			this.attributes = Collections.unmodifiableMap(attributes);
+
+			Object id = attributes.computeIfAbsent(LOG_ID_ATTRIBUTE, name -> ObjectUtils.getIdentityHexString(this));
+			this.logPrefix = "[" + id + "] ";
 		}
 
+
 		@Override
 		public HttpMethod method() {
 			return this.method;
@@ -223,6 +231,11 @@ public Map<String, Object> attributes() {
 			return this.attributes;
 		}
 
+		@Override
+		public String logPrefix() {
+			return this.logPrefix;
+		}
+
 		@Override
 		public Mono<Void> writeTo(ClientHttpRequest request, ExchangeStrategies strategies) {
 			HttpHeaders requestHeaders = request.getHeaders();
@@ -252,7 +265,7 @@ public Optional<ServerHttpRequest> serverRequest() {
 				}
 				@Override
 				public Map<String, Object> hints() {
-					return Hints.none();
+					return Hints.from(Hints.LOG_PREFIX_HINT, logPrefix());
 				}
 			});
 		}

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

@@ -55,11 +55,14 @@ class DefaultClientResponse implements ClientResponse {
 
 	private final ExchangeStrategies strategies;
 
+	private final String logPrefix;
 
-	public DefaultClientResponse(ClientHttpResponse response, ExchangeStrategies strategies) {
+
+	public DefaultClientResponse(ClientHttpResponse response, ExchangeStrategies strategies, String logPrefix) {
 		this.response = response;
 		this.strategies = strategies;
 		this.headers = new DefaultHeaders();
+		this.logPrefix = logPrefix;
 	}
 
 
@@ -96,7 +99,7 @@ public Optional<ServerHttpResponse> serverResponse() {
 			}
 			@Override
 			public Map<String, Object> hints() {
-				return Hints.none();
+				return Hints.from(Hints.LOG_PREFIX_HINT, logPrefix);
 			}
 		});
 	}

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

@@ -129,9 +129,14 @@ private void releaseBody() {
 
 	@Override
 	public ClientResponse build() {
-		ClientHttpResponse clientHttpResponse = new BuiltClientHttpResponse(
-				this.statusCode, this.headers, this.cookies, this.body);
-		return new DefaultClientResponse(clientHttpResponse, this.strategies);
+
+		ClientHttpResponse httpResponse =
+				new BuiltClientHttpResponse(this.statusCode, this.headers, this.cookies, this.body);
+
+		// When building ClientResponse manually, the ClientRequest.logPrefix() has to be passed,
+		// e.g. via ClientResponse.Builder, but this (builder) is not used currently.
+
+		return new DefaultClientResponse(httpResponse, this.strategies, "");
 	}
 
 

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

@@ -91,18 +91,19 @@ public DefaultExchangeFunction(ClientHttpConnector connector, ExchangeStrategies
 
 
 		@Override
-		public Mono<ClientResponse> exchange(ClientRequest request) {
-			Assert.notNull(request, "ClientRequest must not be null");
-			HttpMethod httpMethod = request.method();
-			URI url = request.url();
+		public Mono<ClientResponse> exchange(ClientRequest clientRequest) {
+			Assert.notNull(clientRequest, "ClientRequest must not be null");
+			HttpMethod httpMethod = clientRequest.method();
+			URI url = clientRequest.url();
+			String logPrefix = clientRequest.logPrefix();
 
 			return this.connector
-					.connect(httpMethod, url, httpRequest -> request.writeTo(httpRequest, this.strategies))
-					.doOnRequest(n -> logRequest(request))
-					.doOnCancel(() -> logger.debug("Cancel signal (to close connection)"))
-					.map(response -> {
-						logResponse(response);
-						return new DefaultClientResponse(response, this.strategies);
+					.connect(httpMethod, url, httpRequest -> clientRequest.writeTo(httpRequest, this.strategies))
+					.doOnRequest(n -> logRequest(clientRequest))
+					.doOnCancel(() -> logger.debug(logPrefix + "Cancel signal (to close connection)"))
+					.map(httpResponse -> {
+						logResponse(httpResponse, logPrefix);
+						return new DefaultClientResponse(httpResponse, this.strategies, logPrefix);
 					});
 		}
 
@@ -113,21 +114,21 @@ private void logRequest(ClientRequest request) {
 					int index = formatted.indexOf("?");
 					formatted = (index != -1 ? formatted.substring(0, index) : formatted);
 				}
-				logger.debug("HTTP " + request.method() + " " + formatted);
+				logger.debug(request.logPrefix() + "HTTP " + request.method() + " " + formatted);
 			}
 		}
 
-		private void logResponse(ClientHttpResponse response) {
+		private void logResponse(ClientHttpResponse response, String logPrefix) {
 			if (logger.isDebugEnabled()) {
 				int code = response.getRawStatusCode();
 				HttpStatus status = HttpStatus.resolve(code);
 				String message = "Response " + (status != null ? status : code);
 				if (logger.isTraceEnabled()) {
 					String headers = this.disableLoggingRequestDetails ? "" : ", headers=" + response.getHeaders();
-					logger.trace(message + headers);
+					logger.trace(logPrefix + message + headers);
 				}
 				else {
-					logger.debug(message);
+					logger.debug(logPrefix + message);
 				}
 			}
 		}

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

@@ -68,7 +68,7 @@ public class DefaultClientResponseTests {
 	public void createMocks() {
 		mockResponse = mock(ClientHttpResponse.class);
 		mockExchangeStrategies = mock(ExchangeStrategies.class);
-		defaultClientResponse = new DefaultClientResponse(mockResponse, mockExchangeStrategies);
+		defaultClientResponse = new DefaultClientResponse(mockResponse, mockExchangeStrategies, "");
 	}