Metric endpoint is summing up same metric

spring-boot-project/spring-boot-actuator/src/main/java/org/springframework/boot/actuate/metrics/MetricsEndpoint.java

@@ -16,7 +16,7 @@
 
 package org.springframework.boot.actuate.metrics;
 
-import java.util.ArrayList;
+import java.util.Collection;
 import java.util.Collections;
 import java.util.HashMap;
 import java.util.HashSet;
@@ -81,15 +81,15 @@ private String getName(Meter meter) {
 	public MetricResponse metric(@Selector String requiredMetricName,
 			@Nullable List<String> tag) {
 		List<Tag> tags = parseTags(tag);
-		List<Meter> meters = new ArrayList<>();
-		collectMeters(meters, this.registry, requiredMetricName, tags);
+		Collection<Meter> meters = findFirstMatchingMeters(this.registry,
+				requiredMetricName, tags);
 		if (meters.isEmpty()) {
 			return null;
 		}
 		Map<Statistic, Double> samples = getSamples(meters);
 		Map<String, Set<String>> availableTags = getAvailableTags(meters);
 		tags.forEach((t) -> availableTags.remove(t.getKey()));
-		Meter.Id meterId = meters.get(0).getId();
+		Meter.Id meterId = meters.iterator().next().getId();
 		return new MetricResponse(requiredMetricName, meterId.getDescription(),
 				meterId.getBaseUnit(), asList(samples, Sample::new),
 				asList(availableTags, AvailableTag::new));
@@ -112,18 +112,25 @@ private Tag parseTag(String tag) {
 		return Tag.of(parts[0], parts[1]);
 	}
 
-	private void collectMeters(List<Meter> meters, MeterRegistry registry, String name,
+	private Collection<Meter> findFirstMatchingMeters(MeterRegistry registry, String name,
 			Iterable<Tag> tags) {
 		if (registry instanceof CompositeMeterRegistry) {
-			((CompositeMeterRegistry) registry).getRegistries()
-					.forEach((member) -> collectMeters(meters, member, name, tags));
+			return ((CompositeMeterRegistry) registry).getRegistries().stream()
+					.map((r) -> findFirstMatchingMeters(r, name, tags))
+					.filter((match) -> !match.isEmpty()).findFirst()
+					.orElse(Collections.emptyList());
+
 		}
 		else {
-			meters.addAll(registry.find(name).tags(tags).meters());
+			Collection<Meter> metersFound = registry.find(name).tags(tags).meters();
+			if (!metersFound.isEmpty()) {
+				return metersFound;
+			}
 		}
+		return Collections.emptyList();
 	}
 
-	private Map<Statistic, Double> getSamples(List<Meter> meters) {
+	private Map<Statistic, Double> getSamples(Collection<Meter> meters) {
 		Map<Statistic, Double> samples = new LinkedHashMap<>();
 		meters.forEach((meter) -> mergeMeasurements(samples, meter));
 		return samples;
@@ -138,7 +145,7 @@ private BiFunction<Double, Double, Double> mergeFunction(Statistic statistic) {
 		return Statistic.MAX.equals(statistic) ? Double::max : Double::sum;
 	}
 
-	private Map<String, Set<String>> getAvailableTags(List<Meter> meters) {
+	private Map<String, Set<String>> getAvailableTags(Collection<Meter> meters) {
 		Map<String, Set<String>> availableTags = new HashMap<>();
 		meters.forEach((meter) -> mergeAvailableTags(availableTags, meter));
 		return availableTags;

spring-boot-project/spring-boot-actuator/src/test/java/org/springframework/boot/actuate/metrics/MetricsEndpointTests.java

@@ -95,6 +95,55 @@ public void metricValuesAreTheSumOfAllTimeSeriesMatchingTags() {
 		assertThat(getCount(response)).hasValue(4.0);
 	}
 
+	@Test
+	public void findFirstMatchingMetersFromNestedRegistries() {
+		CompositeMeterRegistry composite = new CompositeMeterRegistry();
+		SimpleMeterRegistry reg1 = new SimpleMeterRegistry();
+		CompositeMeterRegistry reg2 = new CompositeMeterRegistry();
+		SimpleMeterRegistry reg3 = new SimpleMeterRegistry();
+
+		// 1st level nesting
+		composite.add(reg1);
+
+		// 2st level nesting
+		reg2.add(reg3);
+		composite.add(reg2);
+
+		// 2nd level registry has metrics
+		reg3.counter("cache", "result", "hit", "host", "1").increment(2);
+		reg3.counter("cache", "result", "miss", "host", "1").increment(2);
+		reg3.counter("cache", "result", "hit", "host", "2").increment(2);
+
+		MetricsEndpoint endpoint = new MetricsEndpoint(composite);
+
+		MetricsEndpoint.MetricResponse response = endpoint.metric("cache",
+				Collections.emptyList());
+		assertThat(response.getName()).isEqualTo("cache");
+		assertThat(availableTagKeys(response)).containsExactly("result", "host");
+		assertThat(getCount(response)).hasValue(6.0);
+
+		response = endpoint.metric("cache", Collections.singletonList("result:hit"));
+		assertThat(availableTagKeys(response)).containsExactly("host");
+		assertThat(getCount(response)).hasValue(4.0);
+	}
+
+	@Test
+	public void matchingMeterNotFoundInNestedRegistries() {
+		CompositeMeterRegistry composite = new CompositeMeterRegistry();
+		CompositeMeterRegistry reg2 = new CompositeMeterRegistry();
+		SimpleMeterRegistry reg3 = new SimpleMeterRegistry();
+
+		// nested registries
+		reg2.add(reg3);
+		composite.add(reg2);
+
+		MetricsEndpoint endpoint = new MetricsEndpoint(composite);
+
+		MetricsEndpoint.MetricResponse response = endpoint.metric("invalid.metric.name",
+				Collections.emptyList());
+		assertThat(response).isNull();
+	}
+
 	@Test
 	public void metricTagValuesAreDeduplicated() {
 		this.registry.counter("cache", "host", "1", "region", "east", "result", "hit");