Add cache metrics support for LocalResponseCache

spring-cloud-gateway-server-webflux/src/main/java/org/springframework/cloud/gateway/config/LocalResponseCacheAutoConfiguration.java

@@ -21,17 +21,20 @@
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
 
+import org.springframework.beans.factory.ObjectProvider;
 import org.springframework.beans.factory.annotation.Qualifier;
 import org.springframework.boot.autoconfigure.condition.AllNestedConditions;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnProperty;
 import org.springframework.boot.context.properties.EnableConfigurationProperties;
 import org.springframework.cache.Cache;
 import org.springframework.cache.CacheManager;
+import org.springframework.cache.caffeine.CaffeineCache;
 import org.springframework.cache.caffeine.CaffeineCacheManager;
 import org.springframework.cloud.gateway.config.conditional.ConditionalOnEnabledFilter;
 import org.springframework.cloud.gateway.filter.factory.cache.GlobalLocalResponseCacheGatewayFilter;
 import org.springframework.cloud.gateway.filter.factory.cache.LocalResponseCacheGatewayFilterFactory;
+import org.springframework.cloud.gateway.filter.factory.cache.LocalResponseCacheGatewayFilterFactory.CacheMetricsListener;
 import org.springframework.cloud.gateway.filter.factory.cache.LocalResponseCacheProperties;
 import org.springframework.cloud.gateway.filter.factory.cache.LocalResponseCacheUtils;
 import org.springframework.cloud.gateway.filter.factory.cache.ResponseCacheManagerFactory;
@@ -60,10 +63,18 @@ public class LocalResponseCacheAutoConfiguration {
 	@Conditional(LocalResponseCacheAutoConfiguration.OnGlobalLocalResponseCacheCondition.class)
 	public GlobalLocalResponseCacheGatewayFilter globalLocalResponseCacheGatewayFilter(
 			ResponseCacheManagerFactory responseCacheManagerFactory,
-			@Qualifier(RESPONSE_CACHE_MANAGER_NAME) CacheManager cacheManager,
-			LocalResponseCacheProperties properties) {
-		return new GlobalLocalResponseCacheGatewayFilter(responseCacheManagerFactory, responseCache(cacheManager),
-				properties.getTimeToLive(), properties.getRequest());
+			@Qualifier(RESPONSE_CACHE_MANAGER_NAME) CacheManager cacheManager, LocalResponseCacheProperties properties,
+			ObjectProvider<CacheMetricsListener> metricsListenerProvider) {
+		Cache cache = responseCache(cacheManager);
+		CacheMetricsListener listener = metricsListenerProvider.getIfAvailable(() -> CacheMetricsListener.NOOP);
+		if (cache instanceof CaffeineCache caffeineCache) {
+			listener.onCacheCreated(caffeineCache.getNativeCache(), RESPONSE_CACHE_NAME);
+		}
+		else if (listener != CacheMetricsListener.NOOP) {
+			LOGGER.warn("Global response cache is not a CaffeineCache instance; cache metrics will not be registered");
+		}
+		return new GlobalLocalResponseCacheGatewayFilter(responseCacheManagerFactory, cache, properties.getTimeToLive(),
+				properties.getRequest());
 	}
 
 	@Bean(name = RESPONSE_CACHE_MANAGER_NAME)
@@ -74,9 +85,11 @@ public CacheManager gatewayCacheManager(LocalResponseCacheProperties cacheProper
 
 	@Bean
 	public LocalResponseCacheGatewayFilterFactory localResponseCacheGatewayFilterFactory(
-			ResponseCacheManagerFactory responseCacheManagerFactory, LocalResponseCacheProperties properties) {
+			ResponseCacheManagerFactory responseCacheManagerFactory, LocalResponseCacheProperties properties,
+			ObjectProvider<CacheMetricsListener> metricsListenerProvider) {
+		CacheMetricsListener listener = metricsListenerProvider.getIfAvailable(() -> CacheMetricsListener.NOOP);
 		return new LocalResponseCacheGatewayFilterFactory(responseCacheManagerFactory, properties.getTimeToLive(),
-				properties.getSize(), properties.getRequest());
+				properties.getSize(), properties.getRequest(), new CaffeineCacheManager(), listener);
 	}
 
 	@Bean

spring-cloud-gateway-server-webflux/src/main/java/org/springframework/cloud/gateway/config/LocalResponseCacheMetricsAutoConfiguration.java

@@ -0,0 +1,60 @@
+/*
+ * 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.config;
+
+import java.util.Collections;
+
+import com.github.benmanes.caffeine.cache.Caffeine;
+import io.micrometer.core.instrument.MeterRegistry;
+import io.micrometer.core.instrument.binder.cache.CaffeineCacheMetrics;
+
+import org.springframework.boot.autoconfigure.AutoConfigureAfter;
+import org.springframework.boot.autoconfigure.condition.ConditionalOnBean;
+import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
+import org.springframework.boot.autoconfigure.condition.ConditionalOnProperty;
+import org.springframework.boot.micrometer.metrics.autoconfigure.CompositeMeterRegistryAutoConfiguration;
+import org.springframework.boot.micrometer.metrics.autoconfigure.MetricsAutoConfiguration;
+import org.springframework.cache.caffeine.CaffeineCacheManager;
+import org.springframework.cloud.gateway.filter.factory.cache.LocalResponseCacheGatewayFilterFactory.CacheMetricsListener;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.web.reactive.DispatcherHandler;
+
+/**
+ * Auto-configuration for LocalResponseCache metrics. Registers Caffeine cache metrics
+ * with the {@link MeterRegistry} when both the cache infrastructure and Micrometer are
+ * available.
+ *
+ * @author LivingLikeKrillin
+ */
+@Configuration(proxyBeanMethods = false)
+@ConditionalOnProperty(name = GatewayProperties.PREFIX + ".enabled", matchIfMissing = true)
+@AutoConfigureAfter({ LocalResponseCacheAutoConfiguration.class, MetricsAutoConfiguration.class,
+		CompositeMeterRegistryAutoConfiguration.class })
+@ConditionalOnClass({ DispatcherHandler.class, Caffeine.class, CaffeineCacheManager.class, MeterRegistry.class,
+		MetricsAutoConfiguration.class })
+public class LocalResponseCacheMetricsAutoConfiguration {
+
+	@Bean
+	@ConditionalOnBean(MeterRegistry.class)
+	@ConditionalOnProperty(name = GatewayProperties.PREFIX + ".metrics.enabled", matchIfMissing = true)
+	public CacheMetricsListener localResponseCacheMetricsListener(MeterRegistry meterRegistry) {
+		return (cache, cacheName) -> CaffeineCacheMetrics.monitor(meterRegistry, cache, cacheName,
+				Collections.emptyList());
+	}
+
+}

spring-cloud-gateway-server-webflux/src/main/java/org/springframework/cloud/gateway/filter/factory/cache/LocalResponseCacheGatewayFilterFactory.java

@@ -63,20 +63,31 @@ public class LocalResponseCacheGatewayFilterFactory
 
 	private final CaffeineCacheManager caffeineCacheManager;
 
+	private final CacheMetricsListener cacheMetricsListener;
+
 	public LocalResponseCacheGatewayFilterFactory(ResponseCacheManagerFactory cacheManagerFactory,
 			Duration defaultTimeToLive, DataSize defaultSize, RequestOptions requestOptions) {
-		this(cacheManagerFactory, defaultTimeToLive, defaultSize, requestOptions, new CaffeineCacheManager());
+		this(cacheManagerFactory, defaultTimeToLive, defaultSize, requestOptions, new CaffeineCacheManager(),
+				CacheMetricsListener.NOOP);
 	}
 
 	public LocalResponseCacheGatewayFilterFactory(ResponseCacheManagerFactory cacheManagerFactory,
 			Duration defaultTimeToLive, DataSize defaultSize, RequestOptions requestOptions,
 			CaffeineCacheManager caffeineCacheManager) {
+		this(cacheManagerFactory, defaultTimeToLive, defaultSize, requestOptions, caffeineCacheManager,
+				CacheMetricsListener.NOOP);
+	}
+
+	public LocalResponseCacheGatewayFilterFactory(ResponseCacheManagerFactory cacheManagerFactory,
+			Duration defaultTimeToLive, DataSize defaultSize, RequestOptions requestOptions,
+			CaffeineCacheManager caffeineCacheManager, CacheMetricsListener cacheMetricsListener) {
 		super(RouteCacheConfiguration.class);
 		this.cacheManagerFactory = cacheManagerFactory;
 		this.defaultTimeToLive = defaultTimeToLive;
 		this.defaultSize = defaultSize;
 		this.requestOptions = requestOptions;
 		this.caffeineCacheManager = caffeineCacheManager;
+		this.cacheMetricsListener = cacheMetricsListener;
 	}
 
 	@Override
@@ -86,7 +97,9 @@ public GatewayFilter apply(RouteCacheConfiguration config) {
 
 		Caffeine caffeine = LocalResponseCacheUtils.createCaffeine(cacheProperties);
 		String cacheName = config.getRouteId() + "-cache";
-		caffeineCacheManager.registerCustomCache(cacheName, caffeine.build());
+		com.github.benmanes.caffeine.cache.Cache nativeCache = caffeine.build();
+		caffeineCacheManager.registerCustomCache(cacheName, nativeCache);
+		cacheMetricsListener.onCacheCreated(nativeCache, cacheName);
 		Cache routeCache = caffeineCacheManager.getCache(cacheName);
 		Objects.requireNonNull(routeCache, "Cache " + cacheName + " not found");
 		return new ResponseCacheGatewayFilter(
@@ -109,6 +122,24 @@ public List<String> shortcutFieldOrder() {
 		return List.of("timeToLive", "size");
 	}
 
+	/**
+	 * Listener notified when a new Caffeine cache is created, allowing external
+	 * components (e.g., metrics) to observe cache instances.
+	 */
+	@FunctionalInterface
+	public interface CacheMetricsListener {
+
+		// Uses FQN to avoid ambiguity with org.springframework.cache.Cache
+		void onCacheCreated(com.github.benmanes.caffeine.cache.Cache<?, ?> cache, String cacheName);
+
+		/**
+		 * No-op implementation used when metrics infrastructure is not available.
+		 */
+		CacheMetricsListener NOOP = (cache, cacheName) -> {
+		};
+
+	}
+
 	@Validated
 	public static class RouteCacheConfiguration implements HasRouteId {
 

spring-cloud-gateway-server-webflux/src/main/java/org/springframework/cloud/gateway/filter/factory/cache/LocalResponseCacheUtils.java

@@ -48,7 +48,9 @@ public static CaffeineCacheManager createGatewayCacheManager(LocalResponseCacheP
 
 	@SuppressWarnings({ "unchecked", "rawtypes" })
 	public static Caffeine createCaffeine(LocalResponseCacheProperties cacheProperties) {
-		Caffeine caffeine = Caffeine.newBuilder();
+		// Always record stats so metrics are available when Micrometer is present.
+		// The overhead of LongAdder-based stat counters is minimal.
+		Caffeine caffeine = Caffeine.newBuilder().recordStats();
 		LOGGER.info("Initializing Caffeine");
 		Duration ttlSeconds = cacheProperties.getTimeToLive();
 		caffeine.expireAfterWrite(ttlSeconds);

spring-cloud-gateway-server-webflux/src/main/resources/META-INF/spring/org.springframework.boot.autoconfigure.AutoConfiguration.imports

@@ -10,4 +10,5 @@ org.springframework.cloud.gateway.discovery.GatewayDiscoveryClientAutoConfigurat
 org.springframework.cloud.gateway.config.SimpleUrlHandlerMappingGlobalCorsAutoConfiguration
 org.springframework.cloud.gateway.config.GatewayReactiveLoadBalancerClientAutoConfiguration
 org.springframework.cloud.gateway.config.LocalResponseCacheAutoConfiguration
+org.springframework.cloud.gateway.config.LocalResponseCacheMetricsAutoConfiguration
 org.springframework.cloud.gateway.config.GatewayTracingAutoConfiguration

spring-cloud-gateway-server-webflux/src/test/java/org/springframework/cloud/gateway/config/LocalResponseCacheMetricsAutoConfigurationTests.java

@@ -0,0 +1,180 @@
+/*
+ * 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.config;
+
+import java.time.Duration;
+
+import com.github.benmanes.caffeine.cache.Caffeine;
+import io.micrometer.core.instrument.MeterRegistry;
+import io.micrometer.core.instrument.simple.SimpleMeterRegistry;
+import org.junit.jupiter.api.Test;
+
+import org.springframework.boot.autoconfigure.AutoConfigurations;
+import org.springframework.boot.test.context.runner.ApplicationContextRunner;
+import org.springframework.cache.caffeine.CaffeineCacheManager;
+import org.springframework.cloud.gateway.filter.factory.cache.LocalResponseCacheGatewayFilterFactory;
+import org.springframework.cloud.gateway.filter.factory.cache.LocalResponseCacheGatewayFilterFactory.CacheMetricsListener;
+import org.springframework.cloud.gateway.filter.factory.cache.LocalResponseCacheProperties;
+import org.springframework.cloud.gateway.filter.factory.cache.LocalResponseCacheUtils;
+import org.springframework.cloud.gateway.filter.factory.cache.ResponseCacheManagerFactory;
+import org.springframework.cloud.gateway.filter.factory.cache.keygenerator.CacheKeyGenerator;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * Tests for {@link LocalResponseCacheMetricsAutoConfiguration}.
+ *
+ * @author LivingLikeKrillin
+ */
+public class LocalResponseCacheMetricsAutoConfigurationTests {
+
+	@Test
+	void metricsListenerCreatedWhenMeterRegistryPresent() {
+		new ApplicationContextRunner()
+			.withConfiguration(AutoConfigurations.of(LocalResponseCacheAutoConfiguration.class,
+					LocalResponseCacheMetricsAutoConfiguration.class))
+			.withUserConfiguration(MeterRegistryConfig.class)
+			.withPropertyValues(GatewayProperties.PREFIX + ".filter.local-response-cache.enabled=true")
+			.run(context -> {
+				assertThat(context).hasSingleBean(CacheMetricsListener.class);
+			});
+	}
+
+	@Test
+	void metricsListenerNotCreatedWhenMeterRegistryAbsent() {
+		new ApplicationContextRunner()
+			.withConfiguration(AutoConfigurations.of(LocalResponseCacheAutoConfiguration.class,
+					LocalResponseCacheMetricsAutoConfiguration.class))
+			.withPropertyValues(GatewayProperties.PREFIX + ".filter.local-response-cache.enabled=true")
+			.run(context -> {
+				assertThat(context).doesNotHaveBean(CacheMetricsListener.class);
+			});
+	}
+
+	@Test
+	void metricsListenerNotCreatedWhenGatewayDisabled() {
+		new ApplicationContextRunner()
+			.withConfiguration(AutoConfigurations.of(LocalResponseCacheAutoConfiguration.class,
+					LocalResponseCacheMetricsAutoConfiguration.class))
+			.withUserConfiguration(MeterRegistryConfig.class)
+			.withPropertyValues(GatewayProperties.PREFIX + ".filter.local-response-cache.enabled=true",
+					GatewayProperties.PREFIX + ".enabled=false")
+			.run(context -> {
+				assertThat(context).doesNotHaveBean(CacheMetricsListener.class);
+			});
+	}
+
+	@Test
+	void metricsListenerNotCreatedWhenMetricsDisabled() {
+		new ApplicationContextRunner()
+			.withConfiguration(AutoConfigurations.of(LocalResponseCacheAutoConfiguration.class,
+					LocalResponseCacheMetricsAutoConfiguration.class))
+			.withUserConfiguration(MeterRegistryConfig.class)
+			.withPropertyValues(GatewayProperties.PREFIX + ".filter.local-response-cache.enabled=true",
+					GatewayProperties.PREFIX + ".metrics.enabled=false")
+			.run(context -> {
+				assertThat(context).doesNotHaveBean(CacheMetricsListener.class);
+			});
+	}
+
+	@Test
+	void caffeineRecordStatsEnabled() {
+		LocalResponseCacheProperties properties = new LocalResponseCacheProperties();
+		properties.setTimeToLive(Duration.ofMinutes(5));
+		Caffeine<Object, Object> caffeine = LocalResponseCacheUtils.createCaffeine(properties);
+		com.github.benmanes.caffeine.cache.Cache<Object, Object> cache = caffeine.build();
+
+		cache.put("key", "value");
+		cache.getIfPresent("key");
+		cache.getIfPresent("missing");
+
+		assertThat(cache.stats().hitCount()).isEqualTo(1);
+		assertThat(cache.stats().missCount()).isEqualTo(1);
+	}
+
+	@Test
+	void cacheMetricsListenerBindsToMeterRegistry() {
+		SimpleMeterRegistry registry = new SimpleMeterRegistry();
+		LocalResponseCacheProperties properties = new LocalResponseCacheProperties();
+		properties.setTimeToLive(Duration.ofMinutes(5));
+		Caffeine<Object, Object> caffeine = LocalResponseCacheUtils.createCaffeine(properties);
+		com.github.benmanes.caffeine.cache.Cache<Object, Object> cache = caffeine.build();
+
+		new ApplicationContextRunner()
+			.withConfiguration(AutoConfigurations.of(LocalResponseCacheMetricsAutoConfiguration.class))
+			.withBean(MeterRegistry.class, () -> registry)
+			.run(context -> {
+				CacheMetricsListener listener = context.getBean(CacheMetricsListener.class);
+				listener.onCacheCreated(cache, "test-cache");
+
+				cache.put("key", "value");
+				cache.getIfPresent("key");
+
+				assertThat(registry.find("cache.gets").tag("result", "hit").functionCounter()).isNotNull();
+				assertThat(registry.find("cache.size").tag("cache", "test-cache").gauge()).isNotNull();
+			});
+	}
+
+	@Test
+	void globalCacheMetricsRegisteredViaCaffeineCache() {
+		SimpleMeterRegistry registry = new SimpleMeterRegistry();
+		new ApplicationContextRunner()
+			.withConfiguration(AutoConfigurations.of(LocalResponseCacheAutoConfiguration.class,
+					LocalResponseCacheMetricsAutoConfiguration.class))
+			.withBean(MeterRegistry.class, () -> registry)
+			.withPropertyValues(GatewayProperties.PREFIX + ".filter.local-response-cache.enabled=true",
+					GatewayProperties.PREFIX + ".enabled=true",
+					GatewayProperties.PREFIX + ".global-filter.local-response-cache.enabled=true")
+			.run(context -> {
+				assertThat(context).hasSingleBean(CacheMetricsListener.class);
+				assertThat(registry.find("cache.size").tag("cache", "response-cache").gauge()).isNotNull();
+			});
+	}
+
+	@Test
+	void perRouteCacheMetricsRegisteredViaFilterFactory() {
+		SimpleMeterRegistry registry = new SimpleMeterRegistry();
+		CacheMetricsListener listener = (cache,
+				cacheName) -> io.micrometer.core.instrument.binder.cache.CaffeineCacheMetrics.monitor(registry, cache,
+						cacheName, java.util.Collections.emptyList());
+
+		Duration ttl = Duration.ofMinutes(5);
+		ResponseCacheManagerFactory cacheManagerFactory = new ResponseCacheManagerFactory(new CacheKeyGenerator());
+		LocalResponseCacheGatewayFilterFactory factory = new LocalResponseCacheGatewayFilterFactory(cacheManagerFactory,
+				ttl, null, new LocalResponseCacheProperties.RequestOptions(), new CaffeineCacheManager(), listener);
+
+		LocalResponseCacheGatewayFilterFactory.RouteCacheConfiguration routeConfig = new LocalResponseCacheGatewayFilterFactory.RouteCacheConfiguration();
+		routeConfig.setRouteId("my-route");
+		routeConfig.setTimeToLive(ttl);
+		factory.apply(routeConfig);
+
+		assertThat(registry.find("cache.size").tag("cache", "my-route-cache").gauge()).isNotNull();
+	}
+
+	@Configuration(proxyBeanMethods = false)
+	static class MeterRegistryConfig {
+
+		@Bean
+		MeterRegistry meterRegistry() {
+			return new SimpleMeterRegistry();
+		}
+
+	}
+
+}