Correlate data buffers to request log messages

HttpMessageWriter implementations now attach the request log prefix
as a hint to created data buffers when the logger associated with
the writer is at DEBUG level.

Closes gh-26230

spring-web/src/main/java/org/springframework/http/codec/EncoderHttpMessageWriter.java

@@ -57,6 +57,9 @@ import org.springframework.util.StringUtils;
  */
 public class EncoderHttpMessageWriter<T> implements HttpMessageWriter<T> {
 
+	private static final Log logger = HttpLogging.forLogName(EncoderHttpMessageWriter.class);
+
+
 	private final Encoder<T> encoder;
 
 	private final List<MediaType> mediaTypes;
@@ -125,6 +128,7 @@ public class EncoderHttpMessageWriter<T> implements HttpMessageWriter<T> {
 						return message.setComplete().then(Mono.empty());
 					}))
 					.flatMap(buffer -> {
+						Hints.touchDataBuffer(buffer, hints, logger);
 						message.getHeaders().setContentLength(buffer.readableByteCount());
 						return message.writeWith(Mono.just(buffer)
 								.doOnDiscard(PooledDataBuffer.class, DataBufferUtils::release));
@@ -132,10 +136,15 @@ public class EncoderHttpMessageWriter<T> implements HttpMessageWriter<T> {
 		}
 
 		if (isStreamingMediaType(contentType)) {
-			return message.writeAndFlushWith(body.map(buffer ->
-					Mono.just(buffer).doOnDiscard(PooledDataBuffer.class, DataBufferUtils::release)));
+			return message.writeAndFlushWith(body.map(buffer -> {
+				Hints.touchDataBuffer(buffer, hints, logger);
+				return Mono.just(buffer).doOnDiscard(PooledDataBuffer.class, DataBufferUtils::release);
+			}));
 		}
 
+		if (logger.isDebugEnabled()) {
+			body = body.doOnNext(buffer -> Hints.touchDataBuffer(buffer, hints, logger));
+		}
 		return message.writeWith(body);
 	}
 
@@ -166,6 +175,9 @@ public class EncoderHttpMessageWriter<T> implements HttpMessageWriter<T> {
 		return main;
 	}
 
+	private static void touch(DataBuffer buffer, Map<String, Object> hints) {
+	}
+
 	private boolean isStreamingMediaType(@Nullable MediaType mediaType) {
 		if (mediaType == null || !(this.encoder instanceof HttpMessageEncoder)) {
 			return false;

spring-web/src/main/java/org/springframework/http/codec/ResourceHttpMessageWriter.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2019 the original author or authors.
+ * Copyright 2002-2020 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.
@@ -132,6 +132,9 @@ public class ResourceHttpMessageWriter implements HttpMessageWriter<Resource> {
 					Mono<Resource> input = Mono.just(resource);
 					DataBufferFactory factory = message.bufferFactory();
 					Flux<DataBuffer> body = this.encoder.encode(input, factory, type, resourceMediaType, hints);
+					if (logger.isDebugEnabled()) {
+						body = body.doOnNext(buffer -> Hints.touchDataBuffer(buffer, hints, logger));
+					}
 					return message.writeWith(body);
 				});
 	}

spring-web/src/main/java/org/springframework/http/codec/ServerSentEventHttpMessageWriter.java

@@ -23,6 +23,7 @@ import java.util.Collections;
 import java.util.List;
 import java.util.Map;
 
+import org.apache.commons.logging.Log;
 import org.reactivestreams.Publisher;
 import reactor.core.publisher.Flux;
 import reactor.core.publisher.Mono;
@@ -35,6 +36,7 @@ import org.springframework.core.io.buffer.DataBuffer;
 import org.springframework.core.io.buffer.DataBufferFactory;
 import org.springframework.core.io.buffer.DataBufferUtils;
 import org.springframework.core.io.buffer.PooledDataBuffer;
+import org.springframework.http.HttpLogging;
 import org.springframework.http.MediaType;
 import org.springframework.http.ReactiveHttpOutputMessage;
 import org.springframework.http.server.reactive.ServerHttpRequest;
@@ -57,6 +59,8 @@ public class ServerSentEventHttpMessageWriter implements HttpMessageWriter<Objec
 
 	private static final List<MediaType> WRITABLE_MEDIA_TYPES = Collections.singletonList(MediaType.TEXT_EVENT_STREAM);
 
+	private static final Log logger = HttpLogging.forLogName(ServerSentEventHttpMessageWriter.class);
+
 
 	@Nullable
 	private final Encoder<?> encoder;
@@ -167,9 +171,11 @@ public class ServerSentEventHttpMessageWriter implements HttpMessageWriter<Objec
 		if (this.encoder == null) {
 			throw new CodecException("No SSE encoder configured and the data is not String.");
 		}
+		DataBuffer buffer = ((Encoder<T>) this.encoder).encodeValue(data, factory, dataType, mediaType, hints);
+		Hints.touchDataBuffer(buffer, hints, logger);
 		return Flux.just(factory.join(Arrays.asList(
 				encodeText(eventContent, mediaType, factory),
-				((Encoder<T>) this.encoder).encodeValue(data, factory, dataType, mediaType, hints),
+				buffer,
 				encodeText("\n\n", mediaType, factory))));
 	}
 

spring-web/src/main/java/org/springframework/http/codec/multipart/MultipartHttpMessageWriter.java

@@ -199,6 +199,10 @@ public class MultipartHttpMessageWriter extends MultipartWriterSupport
 				.concatWith(generateLastLine(boundary, bufferFactory))
 				.doOnDiscard(PooledDataBuffer.class, DataBufferUtils::release);
 
+		if (logger.isDebugEnabled()) {
+			body = body.doOnNext(buffer -> Hints.touchDataBuffer(buffer, hints, logger));
+		}
+
 		return outputMessage.writeWith(body);
 	}
 

spring-web/src/main/java/org/springframework/http/codec/multipart/PartHttpMessageWriter.java

@@ -69,6 +69,10 @@ public class PartHttpMessageWriter extends MultipartWriterSupport implements Htt
 				.concatWith(generateLastLine(boundary, outputMessage.bufferFactory()))
 				.doOnDiscard(PooledDataBuffer.class, DataBufferUtils::release);
 
+		if (logger.isDebugEnabled()) {
+			body = body.doOnNext(buffer -> Hints.touchDataBuffer(buffer, hints, logger));
+		}
+
 		return outputMessage.writeWith(body);
 	}