Set matching pattern in reactive server observation context

This commit fixes the observation instrumentation for the reactive HTTP
server by setting the best matching pattern determined by the web
framework into the `ServerRequestObservationContext`.

This information is required by the observation convention for creating
the expected `KeyValue` for the matching pattern. Prior to this commit,
the information was missing and resulted in an UNKNOWN key value.

Fixes gh-29422

spring-webflux/src/main/java/org/springframework/web/reactive/function/server/support/RouterFunctionMapping.java

@@ -28,6 +28,7 @@ import org.springframework.http.codec.HttpMessageReader;
 import org.springframework.http.codec.ServerCodecConfigurer;
 import org.springframework.lang.Nullable;
 import org.springframework.util.CollectionUtils;
+import org.springframework.web.filter.reactive.ServerHttpObservationFilter;
 import org.springframework.web.reactive.function.server.HandlerFunction;
 import org.springframework.web.reactive.function.server.RouterFunction;
 import org.springframework.web.reactive.function.server.RouterFunctions;
@@ -170,6 +171,8 @@ public class RouterFunctionMapping extends AbstractHandlerMapping implements Ini
 		PathPattern matchingPattern = (PathPattern) attributes.get(RouterFunctions.MATCHING_PATTERN_ATTRIBUTE);
 		if (matchingPattern != null) {
 			attributes.put(BEST_MATCHING_PATTERN_ATTRIBUTE, matchingPattern);
+			ServerHttpObservationFilter.findObservationContext(serverRequest.exchange())
+					.ifPresent(context -> context.setPathPattern(matchingPattern));
 		}
 		Map<String, String> uriVariables =
 				(Map<String, String>) attributes.get(RouterFunctions.URI_TEMPLATE_VARIABLES_ATTRIBUTE);

spring-webflux/src/main/java/org/springframework/web/reactive/handler/AbstractUrlHandlerMapping.java

@@ -30,6 +30,7 @@ import org.springframework.http.server.PathContainer;
 import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 import org.springframework.util.StringUtils;
+import org.springframework.web.filter.reactive.ServerHttpObservationFilter;
 import org.springframework.web.server.ServerWebExchange;
 import org.springframework.web.util.pattern.PathPattern;
 
@@ -165,6 +166,8 @@ public abstract class AbstractUrlHandlerMapping extends AbstractHandlerMapping {
 
 		exchange.getAttributes().put(BEST_MATCHING_HANDLER_ATTRIBUTE, handler);
 		exchange.getAttributes().put(BEST_MATCHING_PATTERN_ATTRIBUTE, pattern);
+		ServerHttpObservationFilter.findObservationContext(exchange)
+				.ifPresent(context -> context.setPathPattern(pattern));
 		exchange.getAttributes().put(PATH_WITHIN_HANDLER_MAPPING_ATTRIBUTE, pathWithinMapping);
 		exchange.getAttributes().put(URI_TEMPLATE_VARIABLES_ATTRIBUTE, matchInfo.getUriVariables());
 

spring-webflux/src/main/java/org/springframework/web/reactive/result/method/RequestMappingInfoHandlerMapping.java

@@ -38,6 +38,7 @@ import org.springframework.http.server.reactive.ServerHttpRequest;
 import org.springframework.util.Assert;
 import org.springframework.util.MultiValueMap;
 import org.springframework.web.bind.annotation.RequestMethod;
+import org.springframework.web.filter.reactive.ServerHttpObservationFilter;
 import org.springframework.web.method.HandlerMethod;
 import org.springframework.web.reactive.HandlerMapping;
 import org.springframework.web.reactive.result.condition.NameValueExpression;
@@ -139,6 +140,8 @@ public abstract class RequestMappingInfoHandlerMapping extends AbstractHandlerMe
 
 		exchange.getAttributes().put(BEST_MATCHING_HANDLER_ATTRIBUTE, handlerMethod);
 		exchange.getAttributes().put(BEST_MATCHING_PATTERN_ATTRIBUTE, bestPattern);
+		ServerHttpObservationFilter.findObservationContext(exchange)
+				.ifPresent(context -> context.setPathPattern(bestPattern));
 		exchange.getAttributes().put(URI_TEMPLATE_VARIABLES_ATTRIBUTE, uriVariables);
 		exchange.getAttributes().put(MATRIX_VARIABLES_ATTRIBUTE, matrixVariables);
 

spring-webflux/src/test/java/org/springframework/web/reactive/function/server/support/RouterFunctionMappingTests.java

@@ -22,6 +22,8 @@ import reactor.test.StepVerifier;
 
 import org.springframework.context.annotation.AnnotationConfigApplicationContext;
 import org.springframework.http.codec.ServerCodecConfigurer;
+import org.springframework.http.observation.reactive.ServerRequestObservationContext;
+import org.springframework.web.filter.reactive.ServerHttpObservationFilter;
 import org.springframework.web.reactive.HandlerMapping;
 import org.springframework.web.reactive.function.server.HandlerFunction;
 import org.springframework.web.reactive.function.server.RouterFunction;
@@ -34,8 +36,10 @@ import org.springframework.web.testfixture.server.MockServerWebExchange;
 import org.springframework.web.util.pattern.PathPattern;
 
 import static org.assertj.core.api.Assertions.assertThat;
+import static org.springframework.web.filter.reactive.ServerHttpObservationFilter.CURRENT_OBSERVATION_CONTEXT_ATTRIBUTE;
 
 /**
+ * Tests for {@link RouterFunctionMapping}.
  * @author Arjen Poutsma
  * @author Brian Clozel
  */
@@ -132,6 +136,8 @@ class RouterFunctionMappingTests {
 		PathPattern matchingPattern = exchange.getAttribute(HandlerMapping.BEST_MATCHING_PATTERN_ATTRIBUTE);
 		assertThat(matchingPattern).isNotNull();
 		assertThat(matchingPattern.getPatternString()).isEqualTo("/match");
+		assertThat(ServerHttpObservationFilter.findObservationContext(exchange))
+				.hasValueSatisfying(context -> assertThat(context.getPathPattern()).isEqualTo(matchingPattern));
 
 		ServerRequest serverRequest = exchange.getAttribute(RouterFunctions.REQUEST_ATTRIBUTE);
 		assertThat(serverRequest).isNotNull();
@@ -141,7 +147,10 @@ class RouterFunctionMappingTests {
 	}
 
 	private ServerWebExchange createExchange(String urlTemplate) {
-		return MockServerWebExchange.from(MockServerHttpRequest.get(urlTemplate));
+		MockServerWebExchange exchange = MockServerWebExchange.from(MockServerHttpRequest.get(urlTemplate));
+		ServerRequestObservationContext observationContext = new ServerRequestObservationContext(exchange);
+		exchange.getAttributes().put(CURRENT_OBSERVATION_CONTEXT_ATTRIBUTE, observationContext);
+		return exchange;
 	}
 
 }

spring-webflux/src/test/java/org/springframework/web/reactive/result/method/RequestMappingInfoHandlerMappingTests.java

@@ -36,6 +36,7 @@ import org.springframework.core.annotation.AnnotationUtils;
 import org.springframework.http.HttpHeaders;
 import org.springframework.http.HttpMethod;
 import org.springframework.http.MediaType;
+import org.springframework.http.observation.reactive.ServerRequestObservationContext;
 import org.springframework.lang.Nullable;
 import org.springframework.stereotype.Controller;
 import org.springframework.util.ClassUtils;
@@ -63,6 +64,7 @@ import static org.assertj.core.api.Assertions.assertThat;
 import static org.springframework.web.bind.annotation.RequestMethod.GET;
 import static org.springframework.web.bind.annotation.RequestMethod.HEAD;
 import static org.springframework.web.bind.annotation.RequestMethod.OPTIONS;
+import static org.springframework.web.filter.reactive.ServerHttpObservationFilter.CURRENT_OBSERVATION_CONTEXT_ATTRIBUTE;
 import static org.springframework.web.reactive.HandlerMapping.BEST_MATCHING_HANDLER_ATTRIBUTE;
 import static org.springframework.web.reactive.HandlerMapping.BEST_MATCHING_PATTERN_ATTRIBUTE;
 import static org.springframework.web.reactive.result.method.RequestMappingInfo.paths;
@@ -257,6 +259,18 @@ public class RequestMappingInfoHandlerMappingTests {
 		assertThat(mapped).isSameAs(handlerMethod);
 	}
 
+	@Test
+	public void handleMatchBestMatchingPatternAttributeInObservationContext() {
+		RequestMappingInfo key = paths("/{path1}/2", "/**").build();
+		ServerWebExchange exchange = MockServerWebExchange.from(get("/1/2"));
+		ServerRequestObservationContext observationContext = new ServerRequestObservationContext(exchange);
+		exchange.getAttributes().put(CURRENT_OBSERVATION_CONTEXT_ATTRIBUTE, observationContext);
+		this.handlerMapping.handleMatch(key, handlerMethod, exchange);
+
+		assertThat(observationContext.getPathPattern()).isNotNull();
+		assertThat(observationContext.getPathPattern().toString()).isEqualTo("/{path1}/2");
+	}
+
 	@Test // gh-22543
 	public void handleMatchBestMatchingPatternAttributeNoPatternsDefined() {
 		ServerWebExchange exchange = MockServerWebExchange.from(get(""));