Apply config setting for built-in meter name case to extended KPI meter names

webserver/observe/metrics/pom.xml

@@ -1,6 +1,6 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <!--
-    Copyright (c) 2022, 2024 Oracle and/or its affiliates.
+    Copyright (c) 2022, 2025 Oracle and/or its affiliates.
 
     Licensed under the Apache License, Version 2.0 (the "License");
     you may not use this file except in compliance with the License.
@@ -162,6 +162,31 @@
                     </dependency>
                 </dependencies>
             </plugin>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-surefire-plugin</artifactId>
+                <executions>
+                    <execution>
+                        <id>default-test</id>
+                        <configuration>
+                            <excludes>
+                                <exclude>**/TestMetricsConfigPropagation.java</exclude>
+                            </excludes>
+                        </configuration>
+                    </execution>
+                    <execution>
+                        <id>test-config-propagation</id>
+                        <goals>
+                            <goal>test</goal>
+                        </goals>
+                        <configuration>
+                            <includes>
+                                <include>**/TestMetricsConfigPropagation.java</include>
+                            </includes>
+                        </configuration>
+                    </execution>
+                </executions>
+            </plugin>
         </plugins>
     </build>
 </project>

webserver/observe/metrics/src/main/java/io/helidon/webserver/observe/metrics/KeyPerformanceIndicatorMetricsImpls.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2021, 2023 Oracle and/or its affiliates.
+ * Copyright (c) 2021, 2025 Oracle and/or its affiliates.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -22,6 +22,7 @@
 import java.util.Map;
 import java.util.concurrent.atomic.AtomicInteger;
 
+import io.helidon.metrics.api.BuiltInMeterNameFormat;
 import io.helidon.metrics.api.Counter;
 import io.helidon.metrics.api.Gauge;
 import io.helidon.metrics.api.KeyPerformanceIndicatorMetricsConfig;
@@ -55,24 +56,31 @@ class KeyPerformanceIndicatorMetricsImpls {
 
     private static final Map<String, KeyPerformanceIndicatorSupport.Metrics> KPI_METRICS = new HashMap<>();
 
+    // Maps camelCase names to snake_case, but only for those names that are actually different in the two cases.
+    private static final Map<String, String> CAMEL_TO_SNAKE_CASE_METER_NAMES = Map.of("inFlight", "in_flight",
+                                                                                      "longRunning", "long_running");
+
+
     private KeyPerformanceIndicatorMetricsImpls() {
     }
 
     /**
      * Provides a KPI metrics instance.
      *
-     * @param kpiMeterRegistry meter registry holding the KPI metrics
-     * @param meterNamePrefix  prefix to use for the created metrics (e.g., "requests")
-     * @param kpiConfig        KPI metrics config which may influence the construction of the metrics
+     * @param kpiMeterRegistry       meter registry holding the KPI metrics
+     * @param meterNamePrefix        prefix to use for the created metrics (e.g., "requests")
+     * @param kpiConfig              KPI metrics config which may influence the construction of the metrics
+     * @param builtInMeterNameFormat format to use for meter names
      * @return properly prepared new KPI metrics instance
      */
     static KeyPerformanceIndicatorSupport.Metrics get(MeterRegistry kpiMeterRegistry,
                                                       String meterNamePrefix,
-                                                      KeyPerformanceIndicatorMetricsConfig kpiConfig) {
+                                                      KeyPerformanceIndicatorMetricsConfig kpiConfig,
+                                                      BuiltInMeterNameFormat builtInMeterNameFormat) {
         return KPI_METRICS.computeIfAbsent(meterNamePrefix, prefix ->
                 kpiConfig.extended()
-                        ? new Extended(kpiMeterRegistry, meterNamePrefix, kpiConfig)
-                        : new Basic(kpiMeterRegistry, meterNamePrefix));
+                        ? new Extended(kpiMeterRegistry, meterNamePrefix, kpiConfig, builtInMeterNameFormat)
+                        : new Basic(kpiMeterRegistry, meterNamePrefix, builtInMeterNameFormat));
     }
 
     static void close() {
@@ -87,11 +95,13 @@ private static class Basic implements KeyPerformanceIndicatorSupport.Metrics {
         private final Counter totalCount;
         private final MeterRegistry meterRegistry;
         private final List<Meter> meters = new ArrayList<>();
+        private final BuiltInMeterNameFormat builtInMeterNameFormat;
 
-        protected Basic(MeterRegistry kpiMeterRegistry, String meterNamePrefix) {
+        protected Basic(MeterRegistry kpiMeterRegistry, String meterNamePrefix, BuiltInMeterNameFormat builtInMeterNameFormat) {
             meterRegistry = kpiMeterRegistry;
+            this.builtInMeterNameFormat = builtInMeterNameFormat;
             totalCount = add(kpiMeterRegistry.getOrCreate(
-                    Counter.builder(meterNamePrefix + REQUESTS_COUNT_NAME)
+                    Counter.builder(meterNamePrefix + meterName(REQUESTS_COUNT_NAME))
                             .description(
                                     "Each request (regardless of HTTP method) will increase this counter")
                             .scope(KPI_METERS_SCOPE)));
@@ -116,6 +126,12 @@ protected <M extends Meter> M add(M meter) {
         protected Counter totalCount() {
             return totalCount;
         }
+
+        protected String meterName(String camelCaseMeterName){
+            return builtInMeterNameFormat == BuiltInMeterNameFormat.CAMEL
+            ? camelCaseMeterName
+            : CAMEL_TO_SNAKE_CASE_METER_NAMES.getOrDefault(camelCaseMeterName, camelCaseMeterName);
+        }
     }
 
     /**
@@ -136,31 +152,37 @@ private static class Extended extends Basic {
 
         protected Extended(MeterRegistry kpiMeterRegistry,
                            String meterNamePrefix,
-                           KeyPerformanceIndicatorMetricsConfig kpiConfig) {
-            this(kpiMeterRegistry, meterNamePrefix, kpiConfig.longRunningRequestThreshold());
+                           KeyPerformanceIndicatorMetricsConfig kpiConfig,
+                           BuiltInMeterNameFormat builtInMeterNameFormat) {
+            this(kpiMeterRegistry, meterNamePrefix, kpiConfig.longRunningRequestThreshold(), builtInMeterNameFormat);
         }
 
-        private Extended(MeterRegistry kpiMeterRegistry, String meterNamePrefix, Duration longRunningRequestThreshold) {
-            super(kpiMeterRegistry, meterNamePrefix);
+        private Extended(MeterRegistry kpiMeterRegistry,
+                         String meterNamePrefix,
+                         Duration longRunningRequestThreshold,
+                         BuiltInMeterNameFormat builtInMeterNameFormat) {
+            super(kpiMeterRegistry, meterNamePrefix, builtInMeterNameFormat);
             this.longRunningRequestThresdholdMs = longRunningRequestThreshold.toMillis();
 
-            inflightRequests = kpiMeterRegistry.getOrCreate(Gauge.builder(meterNamePrefix + INFLIGHT_REQUESTS_NAME,
-                                                                          inflightRequestsCount,
-                                                                          AtomicInteger::get)
-                                                                    .scope(KPI_METERS_SCOPE));
+            inflightRequests = kpiMeterRegistry.getOrCreate(
+                    Gauge.builder(meterNamePrefix + meterName(INFLIGHT_REQUESTS_NAME),
+                                  inflightRequestsCount,
+                                  AtomicInteger::get)
+                            .scope(KPI_METERS_SCOPE)
+                            .description("Measures the number of requests currently being processed"));
 
             longRunningRequests = kpiMeterRegistry.getOrCreate(
                     Counter.builder(meterNamePrefix + LONG_RUNNING_REQUESTS_NAME)
                             .description("Measures the total number of long-running requests and rates at which they occur")
                             .scope(KPI_METERS_SCOPE)
             );
 
-            load = kpiMeterRegistry.getOrCreate(Counter.builder(meterNamePrefix + LOAD_NAME)
+            load = kpiMeterRegistry.getOrCreate(Counter.builder(meterNamePrefix + meterName(LOAD_NAME))
                                                         .description(LOAD_DESCRIPTION)
                                                         .scope(KPI_METERS_SCOPE));
 
             deferredRequests = new DeferredRequests();
-            kpiMeterRegistry.getOrCreate(Gauge.builder(meterNamePrefix + DEFERRED_NAME,
+            kpiMeterRegistry.getOrCreate(Gauge.builder(meterNamePrefix + meterName(DEFERRED_NAME),
                                                        deferredRequests,
                                                        DeferredRequests::value)
                                                  .description("Measures deferred requests")

webserver/observe/metrics/src/main/java/io/helidon/webserver/observe/metrics/MetricsFeature.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2022, 2024 Oracle and/or its affiliates.
+ * Copyright (c) 2022, 2025 Oracle and/or its affiliates.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -78,7 +78,8 @@ void configureVendorMetrics(HttpRouting.Builder rules) {
                 KeyPerformanceIndicatorMetricsImpls.get(meterRegistry,
                                                         KPI_METER_NAME_PREFIX_WITH_DOT,
                                                         metricsConfig
-                                                                .keyPerformanceIndicatorMetricsConfig());
+                                                                .keyPerformanceIndicatorMetricsConfig(),
+                                                        metricsConfig.builtInMeterNameFormat());
 
         rules.addFilter((chain, req, res) -> {
             KeyPerformanceIndicatorSupport.Context kpiContext = kpiContext(req);

webserver/observe/metrics/src/test/java/io/helidon/webserver/observe/metrics/TestKpiMeterNameCase.java

@@ -0,0 +1,81 @@
+/*
+ * Copyright (c) 2025 Oracle and/or its affiliates.
+ *
+ * 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
+ *
+ *     http://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 io.helidon.webserver.observe.metrics;
+
+import io.helidon.metrics.api.BuiltInMeterNameFormat;
+import io.helidon.metrics.api.KeyPerformanceIndicatorMetricsConfig;
+import io.helidon.metrics.api.MeterRegistry;
+import io.helidon.metrics.api.Metrics;
+import io.helidon.metrics.api.MetricsConfig;
+
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+import static org.hamcrest.MatcherAssert.assertThat;
+import static org.hamcrest.Matchers.hasItem;
+
+class TestKpiMeterNameCase {
+
+    @BeforeEach
+    void clear() {
+        KeyPerformanceIndicatorMetricsImpls.close();
+    }
+
+    @Test
+    void testExtendedWithNoCaseSetting() {
+        MetricsConfig metricsConfig = MetricsConfig.builder()
+                .keyPerformanceIndicatorMetricsConfig(() -> KeyPerformanceIndicatorMetricsConfig.builder()
+                        .extended(true)
+                        .build())
+                .build();
+        MeterRegistry meterRegistry = Metrics.createMeterRegistry(metricsConfig);
+
+        // As a side-effect, the following line registers the KPI metrics in the meter registry.
+        KeyPerformanceIndicatorMetricsImpls.get(meterRegistry,
+                                                "requests.",
+                                                KeyPerformanceIndicatorMetricsConfig.builder().extended(true).build(),
+                                                BuiltInMeterNameFormat.CAMEL);
+
+        assertThat("In-flight KPI",
+                   meterRegistry.meters().stream()
+                           .map(m -> m.id().name())
+                           .toList(),
+                   hasItem("requests.inFlight"));
+    }
+
+    @Test
+    void testExtendedWithSnakeCaseSetting() {
+        MetricsConfig metricsConfig = MetricsConfig.builder()
+                .keyPerformanceIndicatorMetricsConfig(() -> KeyPerformanceIndicatorMetricsConfig.builder()
+                        .extended(true)
+                        .build())
+                .builtInMeterNameFormat(BuiltInMeterNameFormat.SNAKE)
+                .build();
+        MeterRegistry meterRegistry = Metrics.createMeterRegistry(metricsConfig);
+
+        // As a side-effect, the following line registers the KPI metrics in the meter registry.
+        KeyPerformanceIndicatorMetricsImpls.get(meterRegistry,
+                                                "requests.",
+                                                KeyPerformanceIndicatorMetricsConfig.builder().extended(true).build(),
+                                                BuiltInMeterNameFormat.SNAKE);
+
+        assertThat("In-flight KPI",
+                   meterRegistry.meters().stream()
+                           .map(m -> m.id().name())
+                           .toList(),
+                   hasItem("requests.in_flight"));
+    }
+}