Rename gateway client observation metric to avoid WebClient conflict

docs/modules/ROOT/partials/_metrics.adoc

@@ -11,9 +11,9 @@ Observation created when sending a request through the gateway.
 ____
 
 
-**Metric name** `http.client.requests` (defined by convention class `org.springframework.cloud.gateway.filter.headers.observation.DefaultGatewayObservationConvention`). **Type** `timer`.
+**Metric name** `spring.cloud.gateway.http.client.requests` (defined by convention class `org.springframework.cloud.gateway.filter.headers.observation.DefaultGatewayObservationConvention`). **Type** `timer`.
 
-**Metric name** `http.client.requests.active` (defined by convention class `org.springframework.cloud.gateway.filter.headers.observation.DefaultGatewayObservationConvention`). **Type** `long task timer`.
+**Metric name** `spring.cloud.gateway.http.client.requests.active` (defined by convention class `org.springframework.cloud.gateway.filter.headers.observation.DefaultGatewayObservationConvention`). **Type** `long task timer`.
 
 
 IMPORTANT: KeyValues that are added after starting the Observation might be missing from the *.active metrics.

docs/modules/ROOT/partials/_spans.adoc

@@ -8,7 +8,7 @@ Below you can find a list of all spans declared by this project.
 
 > Observation created when sending a request through the gateway.
 
-**Span name** `http.client.requests` (defined by convention class `org.springframework.cloud.gateway.filter.headers.observation.DefaultGatewayObservationConvention`).
+**Span name** `spring.cloud.gateway.http.client.requests` (defined by convention class `org.springframework.cloud.gateway.filter.headers.observation.DefaultGatewayObservationConvention`).
 
 Fully qualified name of the enclosing class `org.springframework.cloud.gateway.filter.headers.observation.GatewayDocumentedObservation`.
 

spring-cloud-gateway-server-webflux/src/main/java/org/springframework/cloud/gateway/filter/headers/observation/DefaultGatewayObservationConvention.java

@@ -70,9 +70,18 @@ public KeyValues getHighCardinalityKeyValues(GatewayContext context) {
 		return KeyValues.of(URI.withValue(context.getRequest().getURI().toString()));
 	}
 
+	/**
+	 * The {@code spring.cloud.gateway.} prefix avoids a metric name collision with Spring
+	 * Web's {@code DefaultClientRequestObservationConvention}, which uses
+	 * {@code http.client.requests} for {@code WebClient} requests with a different
+	 * low-cardinality label set. Without it, Prometheus refuses to register one of the
+	 * two meters and a metric series is dropped.
+	 * @see <a href=
+	 * "https://github.com/spring-cloud/spring-cloud-gateway/issues/3153">gh-3153</a>
+	 */
 	@Override
 	public String getName() {
-		return "http.client.requests";
+		return "spring.cloud.gateway.http.client.requests";
 	}
 
 	@Override

spring-cloud-gateway-server-webflux/src/test/java/org/springframework/cloud/gateway/filter/headers/observation/DefaultGatewayObservationConventionTests.java

@@ -0,0 +1,72 @@
+/*
+ * Copyright 2013-present 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.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.cloud.gateway.filter.headers.observation;
+
+import io.micrometer.common.KeyValue;
+import io.micrometer.common.KeyValues;
+import org.junit.jupiter.api.Test;
+
+import org.springframework.cloud.gateway.route.Route;
+import org.springframework.cloud.gateway.support.ServerWebExchangeUtils;
+import org.springframework.http.HttpHeaders;
+import org.springframework.mock.http.server.reactive.MockServerHttpRequest;
+import org.springframework.mock.web.server.MockServerWebExchange;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+class DefaultGatewayObservationConventionTests {
+
+	@Test
+	void getName_returnsSpringCloudGatewayPrefixedName() {
+		assertThat(DefaultGatewayObservationConvention.INSTANCE.getName())
+			.isEqualTo("spring.cloud.gateway.http.client.requests");
+	}
+
+	@Test
+	void getName_doesNotCollideWithSpringWebClientMetric() {
+		assertThat(DefaultGatewayObservationConvention.INSTANCE.getName()).isNotEqualTo("http.client.requests");
+	}
+
+	@Test
+	void getContextualName_returnsHttpMethodPrefixedName() {
+		MockServerHttpRequest request = MockServerHttpRequest.get("http://localhost:8080/foo").build();
+		MockServerWebExchange exchange = MockServerWebExchange.from(request);
+		GatewayContext context = new GatewayContext(new HttpHeaders(), exchange.getRequest(), exchange);
+
+		assertThat(DefaultGatewayObservationConvention.INSTANCE.getContextualName(context)).isEqualTo("HTTP GET");
+	}
+
+	@Test
+	void getLowCardinalityKeyValues_pinsGatewayRouteKeys() {
+		MockServerHttpRequest request = MockServerHttpRequest.get("http://localhost:8080/foo").build();
+		Route route = Route.async()
+			.id("test-route")
+			.uri("http://localhost:8080/")
+			.order(1)
+			.predicate(exchange -> true)
+			.build();
+		MockServerWebExchange exchange = MockServerWebExchange.from(request);
+		exchange.getAttributes().put(ServerWebExchangeUtils.GATEWAY_ROUTE_ATTR, route);
+		GatewayContext context = new GatewayContext(new HttpHeaders(), exchange.getRequest(), exchange);
+
+		KeyValues keyValues = DefaultGatewayObservationConvention.INSTANCE.getLowCardinalityKeyValues(context);
+
+		assertThat(keyValues.stream().map(KeyValue::getKey)).containsExactlyInAnyOrder("http.method",
+				"http.status_code", "spring.cloud.gateway.route.id", "spring.cloud.gateway.route.uri");
+	}
+
+}

spring-cloud-gateway-server-webflux/src/test/java/org/springframework/cloud/gateway/filter/headers/observation/ObservedHttpHeadersFilterTests.java

@@ -99,11 +99,12 @@ public SampleTestRunnerConsumer yourCode() throws Exception {
 							.hasTag("spring.cloud.gateway.route.uri", "http://localhost:8080/")
 							.hasTag("spring.cloud.gateway.route.id", "foo"));
 			MeterRegistryAssert.then(meterRegistry)
-				.hasTimerWithNameAndTags("http.client.requests",
+				.hasTimerWithNameAndTags("spring.cloud.gateway.http.client.requests",
 						Tags.of("spring.cloud.gateway.route.id", "foo", "error", "none", "http.method", "GET",
 								"http.status_code", "200", "spring.cloud.gateway.route.uri", "http://localhost:8080/"))
-				.hasMeterWithNameAndTags("http.client.requests.active", Tags.of("spring.cloud.gateway.route.id", "foo",
-						"http.method", "GET", "spring.cloud.gateway.route.uri", "http://localhost:8080/"));
+				.hasMeterWithNameAndTags("spring.cloud.gateway.http.client.requests.active",
+						Tags.of("spring.cloud.gateway.route.id", "foo", "http.method", "GET",
+								"spring.cloud.gateway.route.uri", "http://localhost:8080/"));
 		};
 	}