Avoid capturing URI template when interceptor won't use it

Previously, the URI template handler installed by the client metrics
interceptor would always capture the URI template and push it onto the
deque, irrespective of whether auto timing was enabled. When
auto-timing is disabled the deque is never polled so this led to its
unrestricted growth.

This commit updates the URI template handler so that a URI template is
only pushed onto the deque when the auto timing configuration enables
the interceptor.

Fixes gh-26915

spring-boot-project/spring-boot-actuator/src/main/java/org/springframework/boot/actuate/metrics/web/client/MetricsClientHttpRequestInterceptor.java

@@ -77,7 +77,7 @@ class MetricsClientHttpRequestInterceptor implements ClientHttpRequestIntercepto
 	@Override
 	public ClientHttpResponse intercept(HttpRequest request, byte[] body, ClientHttpRequestExecution execution)
 			throws IOException {
-		if (!this.autoTimer.isEnabled()) {
+		if (!enabled()) {
 			return execution.execute(request, body);
 		}
 		long startTime = System.nanoTime();
@@ -100,6 +100,10 @@ class MetricsClientHttpRequestInterceptor implements ClientHttpRequestIntercepto
 		}
 	}
 
+	private boolean enabled() {
+		return this.autoTimer.isEnabled();
+	}
+
 	UriTemplateHandler createUriTemplateHandler(UriTemplateHandler delegate) {
 		if (delegate instanceof RootUriTemplateHandler) {
 			return ((RootUriTemplateHandler) delegate).withHandlerWrapper(CapturingUriTemplateHandler::new);
@@ -113,7 +117,7 @@ class MetricsClientHttpRequestInterceptor implements ClientHttpRequestIntercepto
 				.description("Timer of RestTemplate operation");
 	}
 
-	private static final class CapturingUriTemplateHandler implements UriTemplateHandler {
+	private final class CapturingUriTemplateHandler implements UriTemplateHandler {
 
 		private final UriTemplateHandler delegate;
 
@@ -123,13 +127,17 @@ class MetricsClientHttpRequestInterceptor implements ClientHttpRequestIntercepto
 
 		@Override
 		public URI expand(String url, Map<String, ?> arguments) {
-			urlTemplate.get().push(url);
+			if (enabled()) {
+				urlTemplate.get().push(url);
+			}
 			return this.delegate.expand(url, arguments);
 		}
 
 		@Override
 		public URI expand(String url, Object... arguments) {
-			urlTemplate.get().push(url);
+			if (enabled()) {
+				urlTemplate.get().push(url);
+			}
 			return this.delegate.expand(url, arguments);
 		}
 

spring-boot-project/spring-boot-actuator/src/test/java/org/springframework/boot/actuate/metrics/web/client/MetricsRestTemplateCustomizerTests.java

@@ -19,10 +19,12 @@ package org.springframework.boot.actuate.metrics.web.client;
 import java.io.IOException;
 import java.net.URI;
 import java.net.URISyntaxException;
+import java.util.concurrent.atomic.AtomicBoolean;
 
 import io.micrometer.core.instrument.MeterRegistry;
 import io.micrometer.core.instrument.MockClock;
 import io.micrometer.core.instrument.Tag;
+import io.micrometer.core.instrument.Timer.Builder;
 import io.micrometer.core.instrument.simple.SimpleConfig;
 import io.micrometer.core.instrument.simple.SimpleMeterRegistry;
 import org.assertj.core.api.InstanceOfAssertFactories;
@@ -153,6 +155,39 @@ class MetricsRestTemplateCustomizerTests {
 				.extracting(RootUriTemplateHandler::getRootUri).isEqualTo("https://localhost:8443");
 	}
 
+	@Test
+	void whenAutoTimingIsDisabledUriTemplateHandlerDoesNotCaptureUris() {
+		AtomicBoolean enabled = new AtomicBoolean(false);
+		AutoTimer autoTimer = new AutoTimer() {
+
+			@Override
+			public boolean isEnabled() {
+				return enabled.get();
+			}
+
+			@Override
+			public void apply(Builder builder) {
+			}
+
+		};
+		RestTemplate restTemplate = new RestTemplateBuilder(new MetricsRestTemplateCustomizer(this.registry,
+				new DefaultRestTemplateExchangeTagsProvider(), "http.client.requests", autoTimer)).build();
+		MockRestServiceServer mockServer = MockRestServiceServer.createServer(restTemplate);
+		mockServer.expect(MockRestRequestMatchers.requestTo("/first/123"))
+				.andExpect(MockRestRequestMatchers.method(HttpMethod.GET))
+				.andRespond(MockRestResponseCreators.withSuccess("OK", MediaType.APPLICATION_JSON));
+		mockServer.expect(MockRestRequestMatchers.requestTo("/second/456"))
+				.andExpect(MockRestRequestMatchers.method(HttpMethod.GET))
+				.andRespond(MockRestResponseCreators.withSuccess("OK", MediaType.APPLICATION_JSON));
+		assertThat(restTemplate.getForObject("/first/{id}", String.class, 123)).isEqualTo("OK");
+		assertThat(this.registry.find("http.client.requests").timer()).isNull();
+		enabled.set(true);
+		assertThat(restTemplate.getForObject(URI.create("/second/456"), String.class)).isEqualTo("OK");
+		this.registry.get("http.client.requests").tags("uri", "/second/456").timer();
+		this.mockServer.verify();
+
+	}
+
 	private static final class TestInterceptor implements ClientHttpRequestInterceptor {
 
 		private final RestTemplate restTemplate;