feat: single metric utility method to pick default namespace

Author: Pankaj Agrawal

powertools-metrics/src/main/java/software/amazon/cloudwatchlogs/emf/model/MetricsLoggerHelper.java

@@ -16,7 +16,7 @@ public static long dimensionsCount() {
         return metricsContext().getDimensions().size();
     }
 
-    private static MetricsContext metricsContext() {
+    public static MetricsContext metricsContext() {
         try {
             Field f = metricsLogger().getClass().getDeclaredField("context");
             f.setAccessible(true);

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

@@ -2,7 +2,10 @@
 
 import java.util.function.Consumer;
 
+import software.amazon.cloudwatchlogs.emf.config.SystemWrapper;
 import software.amazon.cloudwatchlogs.emf.logger.MetricsLogger;
+import software.amazon.cloudwatchlogs.emf.model.MetricsContext;
+import software.amazon.cloudwatchlogs.emf.model.MetricsLoggerHelper;
 import software.amazon.cloudwatchlogs.emf.model.Unit;
 
 /**
@@ -26,6 +29,29 @@ public static MetricsLogger metricsLogger() {
         return metricsLogger;
     }
 
+    /**
+     * Add and immediately flush a single metric. It will use the default namespace
+     * specific either on {@link Metrics} annotation or via POWERTOOLS_METRICS_NAMESPACE env var.
+     *
+     * @param name   the name of the metric
+     * @param value  the value of the metric
+     * @param unit   the unit type of the metric
+     * @param logger the MetricsLogger
+     */
+    public static void withSingleMetricOnDefaultNameSpace(final String name,
+                                                          final double value,
+                                                          final Unit unit,
+                                                          final Consumer<MetricsLogger> logger) {
+        MetricsLogger metricsLogger = new MetricsLogger();
+        try {
+            metricsLogger.setNamespace(defaultNameSpace());
+            metricsLogger.putMetric(name, value, unit);
+            logger.accept(metricsLogger);
+        } finally {
+            metricsLogger.flush();
+        }
+    }
+
     /**
      * Add and immediately flush a single metric.
      *
@@ -49,4 +75,10 @@ public static void withSingleMetric(final String name,
             metricsLogger.flush();
         }
     }
+
+    private static String defaultNameSpace() {
+        MetricsContext context = MetricsLoggerHelper.metricsContext();
+        return "aws-embedded-metrics".equals(context.getNamespace()) ?
+                SystemWrapper.getenv("POWERTOOLS_METRICS_NAMESPACE"): context.getNamespace();
+    }
 }

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

@@ -62,6 +62,33 @@ void singleMetricsCaptureUtility() {
         }
     }
 
+    @Test
+    void singleMetricsCaptureUtilityWithDefaultNameSpace() {
+        try (MockedStatic<SystemWrapper> mocked = mockStatic(SystemWrapper.class)) {
+            mocked.when(() -> SystemWrapper.getenv("AWS_EMF_ENVIRONMENT")).thenReturn("Lambda");
+            mocked.when(() -> SystemWrapper.getenv("POWERTOOLS_METRICS_NAMESPACE")).thenReturn("GlobalName");
+
+            MetricsUtils.withSingleMetricOnDefaultNameSpace("Metric1", 1, Unit.COUNT,
+                    metricsLogger -> metricsLogger.setDimensions(DimensionSet.of("Dimension1", "Value1")));
+
+            assertThat(out.toString())
+                    .satisfies(s -> {
+                        Map<String, Object> logAsJson = readAsJson(s);
+
+                        assertThat(logAsJson)
+                                .containsEntry("Metric1", 1.0)
+                                .containsEntry("Dimension1", "Value1")
+                                .containsKey("_aws");
+
+                        Map<String, Object> aws = (Map<String, Object>) logAsJson.get("_aws");
+
+                        assertThat(aws.get("CloudWatchMetrics"))
+                                .asString()
+                                .contains("Namespace=GlobalName");
+                    });
+        }
+    }
+
     private Map<String, Object> readAsJson(String s) {
         try {
             return mapper.readValue(s, Map.class);

powertools-metrics/src/test/java/software/amazon/lambda/powertools/metrics/handlers/PowertoolsMetricsEnabledHandler.java

@@ -3,10 +3,12 @@
 import com.amazonaws.services.lambda.runtime.Context;
 import com.amazonaws.services.lambda.runtime.RequestHandler;
 import software.amazon.cloudwatchlogs.emf.logger.MetricsLogger;
+import software.amazon.cloudwatchlogs.emf.model.DimensionSet;
 import software.amazon.cloudwatchlogs.emf.model.Unit;
 import software.amazon.lambda.powertools.metrics.Metrics;
 
 import static software.amazon.lambda.powertools.metrics.MetricsUtils.metricsLogger;
+import static software.amazon.lambda.powertools.metrics.MetricsUtils.withSingleMetricOnDefaultNameSpace;
 
 public class PowertoolsMetricsEnabledHandler implements RequestHandler<Object, Object> {
 
@@ -16,6 +18,10 @@ public Object handleRequest(Object input, Context context) {
         MetricsLogger metricsLogger = metricsLogger();
         metricsLogger.putMetric("Metric1", 1, Unit.BYTES);
 
+
+        withSingleMetricOnDefaultNameSpace("Metric2", 1, Unit.COUNT,
+                log -> log.setDimensions(DimensionSet.of("Dimension1", "Value1")));
+
         return null;
     }
 }

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

@@ -75,9 +75,23 @@ public void metricsWithoutColdStart() {
             mocked.when(() -> SystemWrapper.getenv("AWS_EMF_ENVIRONMENT")).thenReturn("Lambda");
             requestHandler.handleRequest("input", context);
 
-            assertThat(out.toString())
+            assertThat(out.toString().split("\n"))
+                    .hasSize(2)
                     .satisfies(s -> {
-                        Map<String, Object> logAsJson = readAsJson(s);
+                        Map<String, Object> logAsJson = readAsJson(s[0]);
+
+                        assertThat(logAsJson)
+                                .containsEntry("Metric2", 1.0)
+                                .containsEntry("Dimension1", "Value1")
+                                .containsKey("_aws");
+
+                        Map<String, Object> aws = (Map<String, Object>) logAsJson.get("_aws");
+
+                        assertThat(aws.get("CloudWatchMetrics"))
+                                .asString()
+                                .contains("Namespace=ExampleApplication");
+
+                        logAsJson = readAsJson(s[1]);
 
                         assertThat(logAsJson)
                                 .containsEntry("Metric1", 1.0)