feat: capture metrics even when handler results in exception (#286)

Author: pankajagrawal16

.github/workflows/build.yml

@@ -11,6 +11,7 @@ on:
       - 'powertools-tracing/**'
       - 'powertools-validation/**'
       - 'powertools-parameters/**'
+      - 'powertools-metrics/**'
       - 'pom.xml'
       - '.github/workflows/**'
   push:
@@ -21,8 +22,11 @@ on:
       - 'powertools-logging/**'
       - 'powertools-sqs/**'
       - 'powertools-tracing/**'
+      - 'powertools-validation/**'
+      - 'powertools-parameters/**'
+      - 'powertools-metrics/**'
       - 'pom.xml'
-
+      - '.github/workflows/**'
 jobs:
   build:
     runs-on: ubuntu-latest

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

@@ -53,16 +53,12 @@ public Object around(ProceedingJoinPoint pjp,
             coldStartSingleMetricIfApplicable(pjp, metrics);
 
             try {
-                Object proceed = pjp.proceed(proceedArgs);
+                return pjp.proceed(proceedArgs);
 
+            } finally {
                 coldStartDone();
-
-                validateBeforeFlushingMetrics(metrics);
-
+                validateMetricsAndRefreshOnFailure(metrics);
                 logger.flush();
-                return proceed;
-
-            } finally {
                 refreshMetricsContext();
             }
         }
@@ -105,6 +101,16 @@ private String service(Metrics metrics) {
         return !"".equals(metrics.service()) ? metrics.service() : serviceName();
     }
 
+    private void validateMetricsAndRefreshOnFailure(Metrics metrics) {
+        try {
+
+            validateBeforeFlushingMetrics(metrics);
+        } catch (ValidationException e){
+            refreshMetricsContext();
+            throw e;
+        }
+    }
+
     // This can be simplified after this issues https://github.com/awslabs/aws-embedded-metrics-java/issues/35 is fixed
     private static void refreshMetricsContext() {
         try {

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

@@ -0,0 +1,19 @@
+package software.amazon.lambda.powertools.metrics.handlers;
+
+import com.amazonaws.services.lambda.runtime.Context;
+import com.amazonaws.services.lambda.runtime.RequestHandler;
+import software.amazon.cloudwatchlogs.emf.logger.MetricsLogger;
+import software.amazon.lambda.powertools.metrics.Metrics;
+
+import static software.amazon.lambda.powertools.metrics.MetricsUtils.metricsLogger;
+
+public class PowertoolsMetricsWithExceptionInHandler implements RequestHandler<Object, Object> {
+
+    @Override
+    @Metrics(namespace = "ExampleApplication", service = "booking")
+    public Object handleRequest(Object input, Context context) {
+        MetricsLogger metricsLogger = metricsLogger();
+        metricsLogger.putMetric("CoolMetric", 1);
+        throw new IllegalStateException("Whoops, unexpected exception");
+    }
+}

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

@@ -27,6 +27,7 @@
 import software.amazon.lambda.powertools.metrics.handlers.PowertoolsMetricsNoDimensionsHandler;
 import software.amazon.lambda.powertools.metrics.handlers.PowertoolsMetricsNoExceptionWhenNoMetricsHandler;
 import software.amazon.lambda.powertools.metrics.handlers.PowertoolsMetricsTooManyDimensionsHandler;
+import software.amazon.lambda.powertools.metrics.handlers.PowertoolsMetricsWithExceptionInHandler;
 
 import static java.util.Collections.emptyMap;
 import static org.apache.commons.lang3.reflect.FieldUtils.writeStaticField;
@@ -233,6 +234,26 @@ public void exceptionWhenTooManyDimensionsSet() {
         }
     }
 
+    @Test
+    public void metricsPublishedEvenHandlerThrowsException() {
+        requestHandler = new PowertoolsMetricsWithExceptionInHandler();
+        try (MockedStatic<SystemWrapper> mocked = mockStatic(SystemWrapper.class)) {
+            mocked.when(() -> SystemWrapper.getenv("AWS_EMF_ENVIRONMENT")).thenReturn("Lambda");
+            assertThatExceptionOfType(IllegalStateException.class)
+                    .isThrownBy(() -> requestHandler.handleRequest("input", context))
+                    .withMessage("Whoops, unexpected exception");
+
+            assertThat(out.toString())
+                    .satisfies(s -> {
+                        Map<String, Object> logAsJson = readAsJson(s);
+                        assertThat(logAsJson)
+                                .containsEntry("CoolMetric", 1.0)
+                                .containsEntry("Service", "booking")
+                                .containsKey("_aws");
+                    });
+        }
+    }
+
     private void setupContext() {
         when(context.getFunctionName()).thenReturn("testFunction");
         when(context.getInvokedFunctionArn()).thenReturn("testArn");