emit enhanced error metric and create span when an exception is raised outside of the handler function

Author: TalUsvyatsky

src/handler.cjs

@@ -3,6 +3,7 @@ const {
   datadogHandlerEnvVar,
   lambdaTaskRootEnvVar,
   traceExtractorEnvVar,
+  emitTelemetryOnErrorOutsideHandler,
   getEnvValue,
 } = require("./index.js");
 const { logDebug, logError } = require("./utils/index.js");
@@ -32,4 +33,9 @@ if (extractorEnv) {
   }
 }
 
-exports.handler = datadog(loadSync(taskRootEnv, handlerEnv), { traceExtractor });
+try {
+  exports.handler = datadog(loadSync(taskRootEnv, handlerEnv), { traceExtractor });
+} catch (error) {
+  emitTelemetryOnErrorOutsideHandler(error, handlerEnv, Date.now());
+  throw error;
+}

src/handler.mjs

@@ -1,4 +1,11 @@
-import { datadog, datadogHandlerEnvVar, lambdaTaskRootEnvVar, traceExtractorEnvVar, getEnvValue } from "./index.js";
+import {
+  datadog,
+  datadogHandlerEnvVar,
+  lambdaTaskRootEnvVar,
+  traceExtractorEnvVar,
+  getEnvValue,
+  emitTelemetryOnErrorOutsideHandler,
+} from "./index.js";
 import { logDebug, logError } from "./utils/index.js";
 import { load } from "./runtime/index.js";
 import { initTracer } from "./runtime/module_importer.js";
@@ -26,4 +33,12 @@ if (extractorEnv) {
   }
 }
 
-export const handler = datadog(await load(taskRootEnv, handlerEnv), { traceExtractor });
+let wrapped_handler;
+try {
+  wrapped_handler = datadog(await load(taskRootEnv, handlerEnv), { traceExtractor });
+} catch (error) {
+  emitTelemetryOnErrorOutsideHandler(error, handlerEnv, Date.now());
+  throw error;
+}
+
+export const handler = wrapped_handler;

src/index.ts

@@ -13,6 +13,8 @@ import { subscribeToDC } from "./runtime";
 import { logDebug, Logger, LogLevel, promisifiedHandler, setSandboxInit, setLogger, setLogLevel } from "./utils";
 import { getEnhancedMetricTags } from "./metrics/enhanced-metrics";
 import { DatadogTraceHeaders } from "./trace/context/extractor";
+import { SpanWrapper } from "./trace/span-wrapper";
+import { SpanOptions, TracerWrapper } from "./trace/tracer-wrapper";
 
 // Backwards-compatible export, TODO deprecate in next major
 export { DatadogTraceHeaders as TraceHeaders } from "./trace/context/extractor";
@@ -402,3 +404,26 @@ function getRuntimeTag(): string {
   const version = process.version;
   return `dd_lambda_layer:datadog-node${version}`;
 }
+
+export function emitTelemetryOnErrorOutsideHandler(error: Error, functionName: string, startTime: number): void {
+  const metricsListener = new MetricsListener(new KMSService(), defaultConfig);
+  incrementErrorsMetric(metricsListener);
+  const options: SpanOptions = {
+    tags: {
+      service: "aws.lambda",
+      operation_name: "aws.lambda",
+      resource_names: functionName,
+      "resource.name": functionName,
+      "span.type": "serverless",
+      "error.status": 500,
+      "error.type": typeof error,
+      "error.message": error.message,
+      "error.stack": error.stack,
+      status: error,
+    },
+    startTime,
+  };
+  const tracerWrapper = new TracerWrapper();
+  const span = new SpanWrapper(tracerWrapper.startSpan("aws.lambda", options), {});
+  span.finish();
+}

src/metrics/enhanced-metrics.spec.ts

@@ -55,8 +55,8 @@ describe("getEnhancedMetricTags", () => {
       "account_id:123497598159",
       "functionname:my-test-lambda",
       "resource:my-test-lambda",
-      "cold_start:true",
       "memorysize:128",
+      "cold_start:true",
       "datadog_lambda:vX.X.X",
       "runtime:nodejs20.x",
     ]);
@@ -66,8 +66,8 @@ describe("getEnhancedMetricTags", () => {
     mockedGetProcessVersion.mockReturnValue("v20.9.0");
     expect(getEnhancedMetricTags(mockContextLocal)).toStrictEqual([
       "functionname:my-test-lambda",
-      "cold_start:true",
       "memorysize:128",
+      "cold_start:true",
       "datadog_lambda:vX.X.X",
       "runtime:nodejs20.x",
     ]);
@@ -80,8 +80,8 @@ describe("getEnhancedMetricTags", () => {
       "account_id:123497598159",
       "functionname:my-test-lambda",
       "resource:my-test-lambda",
-      "cold_start:true",
       "memorysize:128",
+      "cold_start:true",
       "datadog_lambda:vX.X.X",
     ]);
   });

src/metrics/enhanced-metrics.ts

@@ -49,12 +49,17 @@ export function getRuntimeTag(): string | null {
   return `runtime:${processVersionTagString}`;
 }
 
-export function getEnhancedMetricTags(context: Context): string[] {
-  let arnTags = [`functionname:${context.functionName}`];
-  if (context.invokedFunctionArn) {
-    arnTags = parseTagsFromARN(context.invokedFunctionArn, context.functionVersion);
+export function getEnhancedMetricTags(context?: Context): string[] {
+  let tags: string[] = [];
+  if (context) {
+    let arnTags = [`functionname:${context.functionName}`];
+    if (context.invokedFunctionArn) {
+      arnTags = parseTagsFromARN(context.invokedFunctionArn, context.functionVersion);
+    }
+    tags = [...arnTags, `memorysize:${context.memoryLimitInMB}`];
   }
-  const tags = [...arnTags, ...getSandboxInitTags(), `memorysize:${context.memoryLimitInMB}`, getVersionTag()];
+
+  tags.push(...getSandboxInitTags(), getVersionTag());
 
   const runtimeTag = getRuntimeTag();
   if (runtimeTag) {
@@ -69,7 +74,7 @@ export function getEnhancedMetricTags(context: Context): string[] {
  * @param context object passed to invocation by AWS
  * @param metricName name of the enhanced metric without namespace prefix, i.e. "invocations" or "errors"
  */
-function incrementEnhancedMetric(listener: MetricsListener, metricName: string, context: Context) {
+function incrementEnhancedMetric(listener: MetricsListener, metricName: string, context?: Context) {
   // Always write enhanced metrics to standard out
   listener.sendDistributionMetric(`aws.lambda.enhanced.${metricName}`, 1, true, ...getEnhancedMetricTags(context));
 }
@@ -78,6 +83,6 @@ export function incrementInvocationsMetric(listener: MetricsListener, context: C
   incrementEnhancedMetric(listener, "invocations", context);
 }
 
-export function incrementErrorsMetric(listener: MetricsListener, context: Context): void {
+export function incrementErrorsMetric(listener: MetricsListener, context?: Context): void {
   incrementEnhancedMetric(listener, "errors", context);
 }