Additional DataBuffer hints

See gh-26230

spring-web/src/main/java/org/springframework/http/codec/json/AbstractJackson2Encoder.java

@@ -223,6 +223,7 @@ public abstract class AbstractJackson2Encoder extends Jackson2CodecSupport imple
 			byte[] bytes = byteBuilder.toByteArray();
 			DataBuffer buffer = bufferFactory.allocateBuffer(bytes.length);
 			buffer.write(bytes);
+			Hints.touchDataBuffer(buffer, hints, logger);
 
 			return buffer;
 		}
@@ -267,6 +268,7 @@ public abstract class AbstractJackson2Encoder extends Jackson2CodecSupport imple
 		DataBuffer buffer = bufferFactory.allocateBuffer(length + separator.length);
 		buffer.write(bytes, offset, length);
 		buffer.write(separator);
+		Hints.touchDataBuffer(buffer, hints, logger);
 
 		return buffer;
 	}

spring-web/src/main/java/org/springframework/http/server/reactive/AbstractServerHttpResponse.java

@@ -211,16 +211,18 @@ public abstract class AbstractServerHttpResponse implements ServerHttpResponse {
 		// We must resolve value first however, for a chance to handle potential error.
 		if (body instanceof Mono) {
 			return ((Mono<? extends DataBuffer>) body)
-					.flatMap(buffer ->
-							doCommit(() -> {
-								try {
-									return writeWithInternal(Mono.fromCallable(() -> buffer)
-											.doOnDiscard(PooledDataBuffer.class, DataBufferUtils::release));
-								}
-								catch (Throwable ex) {
-									return Mono.error(ex);
-								}
-							}).doOnError(ex -> DataBufferUtils.release(buffer)))
+					.flatMap(buffer -> {
+						touchDataBuffer(buffer);
+						return doCommit(() -> {
+							try {
+								return writeWithInternal(Mono.fromCallable(() -> buffer)
+										.doOnDiscard(PooledDataBuffer.class, DataBufferUtils::release));
+							}
+							catch (Throwable ex) {
+								return Mono.error(ex);
+							}
+						}).doOnError(ex -> DataBufferUtils.release(buffer));
+					})
 					.doOnError(t -> getHeaders().clearContentHeaders());
 		}
 		else {
@@ -323,4 +325,13 @@ public abstract class AbstractServerHttpResponse implements ServerHttpResponse {
 	 */
 	protected abstract void applyCookies();
 
+	/**
+	 * Allow sub-classes to associate a hint with the data buffer if it is a
+	 * pooled buffer and supports leak tracking.
+	 * @param buffer the buffer to attach a hint to
+	 * @since 5.3.2
+	 */
+	protected void touchDataBuffer(DataBuffer buffer) {
+	}
+
 }

spring-web/src/main/java/org/springframework/http/server/reactive/ReactorServerHttpResponse.java

@@ -20,6 +20,9 @@ import java.nio.file.Path;
 import java.util.List;
 
 import io.netty.buffer.ByteBuf;
+import io.netty.channel.ChannelId;
+import org.apache.commons.logging.Log;
+import org.apache.commons.logging.LogFactory;
 import org.reactivestreams.Publisher;
 import reactor.core.publisher.Flux;
 import reactor.core.publisher.Mono;
@@ -27,6 +30,7 @@ import reactor.netty.http.server.HttpServerResponse;
 
 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.NettyDataBufferFactory;
 import org.springframework.http.HttpHeaders;
 import org.springframework.http.HttpStatus;
@@ -43,6 +47,9 @@ import org.springframework.util.Assert;
  */
 class ReactorServerHttpResponse extends AbstractServerHttpResponse implements ZeroCopyHttpOutputMessage {
 
+	private static final Log logger = LogFactory.getLog(ReactorServerHttpResponse.class);
+
+
 	private final HttpServerResponse response;
 
 
@@ -115,4 +122,14 @@ class ReactorServerHttpResponse extends AbstractServerHttpResponse implements Ze
 				Flux.from(dataBuffers).map(NettyDataBufferFactory::toByteBuf);
 	}
 
+	@Override
+	protected void touchDataBuffer(DataBuffer buffer) {
+		if (logger.isDebugEnabled()) {
+			this.response.withConnection(connection -> {
+				ChannelId id = connection.channel().id();
+				DataBufferUtils.touch(buffer, "Channel id: " + id.asShortText());
+			});
+		}
+	}
+
 }