When cache names clash include clash manager name in all prefixes

Previously, when multiple cache managers had a cache with the same name,
the prefix for the first cache that was processed would not include its
cache manager’s name, but all subsequent prefixes would include the
cache manager’s name. This was inconsistent, and due to the cache
managers being unordered, the prefixing was not deterministic.

This commit updates the prefixing logic so that when there is a clash,
all of the affected prefixes will include the name of the cache manager.
For example, with cache managers named first and second and each
with a cache named users, the prefixes will be cache.first_users and
cache.second_users rather than cache.users and
cache.{first|second}_users.

Closes gh-2824

spring-boot-actuator/src/main/java/org/springframework/boot/actuate/endpoint/CachePublicMetrics.java

@@ -16,10 +16,12 @@
 
 package org.springframework.boot.actuate.endpoint;
 
+import java.util.ArrayList;
 import java.util.Collection;
+import java.util.HashMap;
 import java.util.HashSet;
+import java.util.List;
 import java.util.Map;
-import java.util.Set;
 
 import javax.annotation.PostConstruct;
 
@@ -54,8 +56,8 @@ public class CachePublicMetrics implements PublicMetrics {
 
 	@Override
 	public Collection<Metric<?>> metrics() {
-		Set<String> targetNames = new HashSet<String>();
 		Collection<Metric<?>> metrics = new HashSet<Metric<?>>();
+		Map<String, List<String>> cacheManagerNamesByCacheName = getCacheManagerNamesByCacheName();
 		for (Map.Entry<String, CacheManager> entry : this.cacheManagers.entrySet()) {
 			String cacheManagerName = entry.getKey();
 			CacheManager cacheManager = entry.getValue();
@@ -64,8 +66,8 @@ public class CachePublicMetrics implements PublicMetrics {
 				CacheStatistics cacheStatistics = this.cacheStatisticsProvider
 						.getCacheStatistics(cache, cacheManager);
 				if (cacheStatistics != null) {
-					String prefix = cleanPrefix(createPrefix(targetNames, cacheName,
-							cacheManagerName));
+					String prefix = cleanPrefix(createPrefix(
+							cacheManagerNamesByCacheName, cacheName, cacheManagerName));
 					metrics.addAll(cacheStatistics.toMetrics(prefix));
 				}
 			}
@@ -73,22 +75,38 @@ public class CachePublicMetrics implements PublicMetrics {
 		return metrics;
 	}
 
+	private Map<String, List<String>> getCacheManagerNamesByCacheName() {
+		Map<String, List<String>> cacheManagerNamesByCacheName = new HashMap<String, List<String>>();
+		for (Map.Entry<String, CacheManager> entry : this.cacheManagers.entrySet()) {
+			for (String cacheName : entry.getValue().getCacheNames()) {
+				List<String> cacheManagerNames = cacheManagerNamesByCacheName
+						.get(cacheName);
+				if (cacheManagerNames == null) {
+					cacheManagerNames = new ArrayList<String>();
+					cacheManagerNamesByCacheName.put(cacheName, cacheManagerNames);
+				}
+				cacheManagerNames.add(entry.getKey());
+			}
+		}
+		return cacheManagerNamesByCacheName;
+	}
+
 	/**
-	 * Create the prefix to use for the specified cache. The specified {@code targetNames}
-	 * set contains the names that have been acquired so far.
-	 * @param targetNames the target names that have been used for other caches
+	 * Create the prefix to use for the specified cache. The generated prefix should be
+	 * unique among those that will be generated for the given map of cache names
+	 * @param cacheManagerNamesByCacheName a mapping of cache names to the names of the
+	 * cache managers that have a cache with that name
 	 * @param cacheName the name of the cache
 	 * @param cacheManagerName the name of its cache manager
 	 * @return a prefix to use for the specified cache
 	 */
-	protected String createPrefix(Set<String> targetNames, String cacheName,
-			String cacheManagerName) {
-		if (targetNames.contains(cacheName)) {
+	protected String createPrefix(Map<String, List<String>> cacheManagerNamesByCacheName,
+			String cacheName, String cacheManagerName) {
+		if (cacheManagerNamesByCacheName.get(cacheName).size() > 1) {
 			String target = cacheManagerName + "_" + cacheName;
 			return createPrefixFor(target);
 		}
 		else {
-			targetNames.add(cacheName);
 			return createPrefixFor(cacheName);
 		}
 	}

spring-boot-actuator/src/test/java/org/springframework/boot/actuate/autoconfigure/PublicMetricsAutoConfigurationTests.java

@@ -218,7 +218,7 @@ public class PublicMetricsAutoConfigurationTests {
 		CachePublicMetrics bean = this.context.getBean(CachePublicMetrics.class);
 		Collection<Metric<?>> metrics = bean.metrics();
 		assertMetrics(metrics, "cache.books.size", "cache.second_speakers.size",
-				"cache.speakers.size", "cache.users.size");
+				"cache.first_speakers.size", "cache.users.size");
 	}
 
 	private void assertHasMetric(Collection<Metric<?>> metrics, Metric<?> metric) {