Only add service name dimension if the service is actually defined.

Author: phipag

powertools-metrics/src/main/java/software/amazon/lambda/powertools/metrics/MetricsLoggerFactory.java

@@ -14,9 +14,9 @@
 
 package software.amazon.lambda.powertools.metrics;
 
-import software.amazon.lambda.powertools.metrics.model.DimensionSet;
-
+import software.amazon.lambda.powertools.common.internal.LambdaConstants;
 import software.amazon.lambda.powertools.common.internal.LambdaHandlerProcessor;
+import software.amazon.lambda.powertools.metrics.model.DimensionSet;
 import software.amazon.lambda.powertools.metrics.provider.EmfMetricsProvider;
 import software.amazon.lambda.powertools.metrics.provider.MetricsProvider;
 
@@ -45,7 +45,11 @@ public static synchronized MetricsLogger getMetricsLogger() {
                 metricsLogger.setNamespace(envNamespace);
             }
 
-            metricsLogger.setDefaultDimensions(DimensionSet.of("Service", LambdaHandlerProcessor.serviceName()));
+            // Only set Service dimension if it's not the default undefined value
+            String serviceName = LambdaHandlerProcessor.serviceName();
+            if (!LambdaConstants.SERVICE_UNDEFINED.equals(serviceName)) {
+                metricsLogger.setDefaultDimensions(DimensionSet.of("Service", serviceName));
+            }
         }
 
         return metricsLogger;

powertools-metrics/src/main/java/software/amazon/lambda/powertools/metrics/internal/LambdaMetricsAspect.java

@@ -25,6 +25,7 @@
 
 import com.amazonaws.services.lambda.runtime.Context;
 
+import software.amazon.lambda.powertools.common.internal.LambdaConstants;
 import software.amazon.lambda.powertools.common.internal.LambdaHandlerProcessor;
 import software.amazon.lambda.powertools.metrics.Metrics;
 import software.amazon.lambda.powertools.metrics.MetricsLogger;
@@ -70,12 +71,10 @@ public Object around(ProceedingJoinPoint pjp,
                 logger.setNamespace(metrics.namespace());
             }
 
-            // If the default dimensions are larger than 1 or do not contain the "Service" dimension, it means that the
-            // user overwrote them manually e.g. using MetricsLoggerBuilder. In this case, we don't set the service
-            // default dimension.
-            if (!"".equals(metrics.service())
-                    && logger.getDefaultDimensions().getDimensionKeys().size() <= 1
-                    && logger.getDefaultDimensions().getDimensionKeys().contains(SERVICE_DIMENSION)) {
+            // We only overwrite the default dimensions if the user didn't overwrite them previously. This means that
+            // they are either empty or only contain the default "Service" dimension.
+            if (!"".equals(metrics.service().trim()) && (logger.getDefaultDimensions().getDimensionKeys().size() <= 1
+                    || logger.getDefaultDimensions().getDimensionKeys().contains(SERVICE_DIMENSION))) {
                 logger.setDefaultDimensions(DimensionSet.of(SERVICE_DIMENSION, metrics.service()));
             }
 
@@ -95,12 +94,20 @@ public Object around(ProceedingJoinPoint pjp,
                     // Get function name from annotation or context
                     String funcName = functionName(metrics, extractedContext);
 
-                    // Create dimensions with service and function name
-                    DimensionSet coldStartDimensions = DimensionSet.of(
-                            SERVICE_DIMENSION,
-                            logger.getDefaultDimensions().getDimensions().getOrDefault(SERVICE_DIMENSION,
-                                    serviceNameWithFallback(metrics)),
-                            "FunctionName", funcName != null ? funcName : extractedContext.getFunctionName());
+                    DimensionSet coldStartDimensions = new DimensionSet();
+
+                    // Get service name from logger default dimensions or fallback
+                    String serviceName = logger.getDefaultDimensions().getDimensions().getOrDefault(SERVICE_DIMENSION,
+                            serviceNameWithFallback(metrics));
+
+                    // Only add service if it is not undefined
+                    if (!LambdaConstants.SERVICE_UNDEFINED.equals(serviceName)) {
+                        coldStartDimensions.addDimension(SERVICE_DIMENSION, serviceName);
+                    }
+
+                    // Add function name
+                    coldStartDimensions.addDimension("FunctionName",
+                            funcName != null ? funcName : extractedContext.getFunctionName());
 
                     logger.captureColdStartMetric(extractedContext, coldStartDimensions);
                 }

powertools-metrics/src/test/java/software/amazon/lambda/powertools/metrics/ConfigurationPrecedenceTest.java

@@ -179,8 +179,8 @@ void shouldUseDefaultsWhenNoConfiguration() throws Exception {
         // Default values should be used
         assertThat(rootNode.get("_aws").get("CloudWatchMetrics").get(0).get("Namespace").asText())
                 .isEqualTo("TestNamespace");
-        assertThat(rootNode.has("Service")).isTrue();
-        assertThat(rootNode.get("Service").asText()).isEqualTo("service_undefined");
+        // Service dimension should not be present when service is undefined
+        assertThat(rootNode.has("Service")).isFalse();
     }
 
     private static class HandlerWithMetricsAnnotation implements RequestHandler<Map<String, Object>, String> {

powertools-metrics/src/test/java/software/amazon/lambda/powertools/metrics/MetricsLoggerFactoryTest.java

@@ -146,4 +146,21 @@ void shouldThrowExceptionWhenSettingNullProvider() {
                 .hasMessage("Metrics provider cannot be null");
     }
 
+    @Test
+    void shouldNotSetServiceDimensionWhenServiceUndefined() throws Exception {
+        // Given - no POWERTOOLS_SERVICE_NAME set, so it will use the default undefined value
+
+        // When
+        MetricsLogger metricsLogger = MetricsLoggerFactory.getMetricsLogger();
+        metricsLogger.setNamespace("TestNamespace");
+        metricsLogger.addMetric("test-metric", 100, MetricUnit.COUNT);
+        metricsLogger.flush();
+
+        // Then
+        String emfOutput = outputStreamCaptor.toString().trim();
+        JsonNode rootNode = objectMapper.readTree(emfOutput);
+
+        // Service dimension should not be present
+        assertThat(rootNode.has("Service")).isFalse();
+    }
 }

powertools-metrics/src/test/java/software/amazon/lambda/powertools/metrics/internal/LambdaMetricsAspectTest.java

@@ -161,6 +161,34 @@ void shouldCaptureColdStartMetricWhenConfigured() throws Exception {
         assertThat(metricsNode.has("test-metric")).isTrue();
     }
 
+    @Test
+    void shouldNotIncludeServiceDimensionInColdStartMetricWhenServiceUndefined() throws Exception {
+        // Given - no service name set, so it will use the default undefined value
+        RequestHandler<Map<String, Object>, String> handler = new HandlerWithColdStartMetricsAnnotation();
+        Context context = new TestContext();
+        Map<String, Object> input = new HashMap<>();
+
+        // When
+        handler.handleRequest(input, context);
+
+        // Then
+        String emfOutput = outputStreamCaptor.toString().trim();
+        String[] emfOutputs = emfOutput.split("\\n");
+
+        // There should be two EMF outputs - one for cold start and one for the handler metrics
+        assertThat(emfOutputs).hasSize(2);
+
+        JsonNode coldStartNode = objectMapper.readTree(emfOutputs[0]);
+        assertThat(coldStartNode.has("ColdStart")).isTrue();
+        assertThat(coldStartNode.get("ColdStart").asDouble()).isEqualTo(1.0);
+
+        // Service dimension should not be present in cold start metrics
+        assertThat(coldStartNode.has("Service")).isFalse();
+
+        // FunctionName dimension should be present
+        assertThat(coldStartNode.has("FunctionName")).isTrue();
+    }
+
     @Test
     void shouldUseCustomFunctionNameWhenProvidedForColdStartMetric() throws Exception {
         // Given