From 9910df85cd5f0f326f588928c7e3078cd38c1453 Mon Sep 17 00:00:00 2001
From: Brian Clozel <brian.clozel@broadcom.com>
Date: Tue, 12 Mar 2024 09:49:00 +0100
Subject: [PATCH] Remove observation context from ClientRequest

Prior to this commit, gh-31609 added the current observation context as
a request attribute for `WebClient` calls. While it was not confirmed as
the main cause, this feature was linked to several reports of memory
leaks. This would indeed attach more memory to the request object graph
at runtime - although it shouldn't prevent its collection by the GC.

This commit removes this feature and instead developers should get the
current observation from the reactor context if they wish to interact
with it.

Closes gh-32198
---
 .../ClientRequestObservationContext.java      | 21 -------------------
 .../function/client/DefaultWebClient.java     |  4 +---
 .../client/WebClientObservationTests.java     | 17 ---------------
 3 files changed, 1 insertion(+), 41 deletions(-)

diff --git a/spring-webflux/src/main/java/org/springframework/web/reactive/function/client/ClientRequestObservationContext.java b/spring-webflux/src/main/java/org/springframework/web/reactive/function/client/ClientRequestObservationContext.java
index 926684eba85..deba7061c09 100644
--- a/spring-webflux/src/main/java/org/springframework/web/reactive/function/client/ClientRequestObservationContext.java
+++ b/spring-webflux/src/main/java/org/springframework/web/reactive/function/client/ClientRequestObservationContext.java
@@ -16,8 +16,6 @@
 
 package org.springframework.web.reactive.function.client;
 
-import java.util.Optional;
-
 import io.micrometer.observation.transport.RequestReplySenderContext;
 
 import org.springframework.lang.Nullable;
@@ -35,14 +33,6 @@ import org.springframework.lang.Nullable;
  */
 public class ClientRequestObservationContext extends RequestReplySenderContext<ClientRequest.Builder, ClientResponse> {
 
-	/**
-	 * Name of the request attribute holding the {@link ClientRequestObservationContext context}
-	 * for the current observation.
-	 * @since 6.0.15
-	 */
-	public static final String CURRENT_OBSERVATION_CONTEXT_ATTRIBUTE = ClientRequestObservationContext.class.getName();
-
-
 	@Nullable
 	private String uriTemplate;
 
@@ -127,15 +117,4 @@ public class ClientRequestObservationContext extends RequestReplySenderContext<C
 	}
 
 
-	/**
-	 * Get the current {@link ClientRequestObservationContext observation context}
-	 * from the given request, if available.
-	 * @param request the current client request
-	 * @return the current observation context
-	 * @since 6.0.15
-	 */
-	public static Optional<ClientRequestObservationContext> findCurrent(ClientRequest request) {
-		return Optional.ofNullable((ClientRequestObservationContext) request.attributes().get(CURRENT_OBSERVATION_CONTEXT_ATTRIBUTE));
-	}
-
 }
diff --git a/spring-webflux/src/main/java/org/springframework/web/reactive/function/client/DefaultWebClient.java b/spring-webflux/src/main/java/org/springframework/web/reactive/function/client/DefaultWebClient.java
index 425e08336d9..296bacb41d9 100644
--- a/spring-webflux/src/main/java/org/springframework/web/reactive/function/client/DefaultWebClient.java
+++ b/spring-webflux/src/main/java/org/springframework/web/reactive/function/client/DefaultWebClient.java
@@ -450,9 +450,7 @@ final class DefaultWebClient implements WebClient {
 				if (filterFunctions != null) {
 					filterFunction = filterFunctions.andThen(filterFunction);
 				}
-				ClientRequest request = requestBuilder
-						.attribute(ClientRequestObservationContext.CURRENT_OBSERVATION_CONTEXT_ATTRIBUTE, observationContext)
-						.build();
+				ClientRequest request = requestBuilder.build();
 				observationContext.setUriTemplate((String) request.attribute(URI_TEMPLATE_ATTRIBUTE).orElse(null));
 				observationContext.setRequest(request);
 				Mono<ClientResponse> responseMono = filterFunction.apply(exchangeFunction)
diff --git a/spring-webflux/src/test/java/org/springframework/web/reactive/function/client/WebClientObservationTests.java b/spring-webflux/src/test/java/org/springframework/web/reactive/function/client/WebClientObservationTests.java
index 3ef2cdda489..73a35047e14 100644
--- a/spring-webflux/src/test/java/org/springframework/web/reactive/function/client/WebClientObservationTests.java
+++ b/spring-webflux/src/test/java/org/springframework/web/reactive/function/client/WebClientObservationTests.java
@@ -148,23 +148,6 @@ class WebClientObservationTests {
 		verifyAndGetRequest();
 	}
 
-	@Test
-	void setsCurrentObservationContextAsRequestAttribute() {
-		ExchangeFilterFunction assertionFilter = (request, chain) -> {
-			Optional<ClientRequestObservationContext> observationContext = ClientRequestObservationContext.findCurrent(request);
-			assertThat(observationContext).isPresent();
-			return chain.exchange(request).contextWrite(context -> {
-				Observation currentObservation = context.get(ObservationThreadLocalAccessor.KEY);
-				assertThat(currentObservation.getContext()).isEqualTo(observationContext.get());
-				return context;
-			});
-		};
-		this.builder.filter(assertionFilter).build().get().uri("/resource/{id}", 42)
-				.retrieve().bodyToMono(Void.class)
-				.block(Duration.ofSeconds(10));
-		verifyAndGetRequest();
-	}
-
 	@Test
 	void recordsObservationWithResponseDetailsWhenFilterFunctionErrors() {
 		ExchangeFilterFunction errorFunction = (req, next) -> next.exchange(req).then(Mono.error(new IllegalStateException()));