add workaround

Author: Raphael Manke

Diff for: lib/node-18-fetch-with-tracing.ts

@@ -0,0 +1,129 @@
+import { LambdaInterface } from "@aws-lambda-powertools/commons";
+import { Tracer } from "@aws-lambda-powertools/tracer";
+import nodeFetch from "node-fetch";
+import * as diagnosticsChannel from "diagnostics_channel";
+
+import { Subsegment, Segment } from "aws-xray-sdk-core";
+
+const lambdaTracer = new Tracer();
+
+export class Lambda implements LambdaInterface {
+  // Decorate your handler class method
+
+  constructor() {
+    addNativeFetchTracing(lambdaTracer);
+  }
+
+  @lambdaTracer.captureMethod()
+  public async nativeFetch() {
+    const response = await fetch("https://api.github.com/users/aws-samples");
+    const json = await response.json();
+    return json;
+  }
+
+  @lambdaTracer.captureMethod()
+  public async nodeFetch() {
+    const response = await nodeFetch(
+      "https://api.github.com/users/aws-samples"
+    );
+    const json = await response.json();
+    return json;
+  }
+
+  public async handler(_event: unknown, _context: unknown): Promise<void> {
+    await this.nativeFetch();
+    await this.nodeFetch();
+  }
+}
+
+const handlerClass = new Lambda();
+export const handler = handlerClass.handler.bind(handlerClass); //
+
+const segments = new Map<
+  any,
+  { subsegment: Subsegment; parentSubsegment: Segment | Subsegment }
+>();
+
+function addNativeFetchTracing(tracer: Tracer) {
+  /**
+   * This is the first event emitted when a request is created.
+   * Based on this event a new subsegment is created.
+   * To have a reference to the subsegment created, it is stored in a map.
+   */
+  diagnosticsChannel
+    .channel("undici:request:create")
+    .subscribe(({ request }: any) => {
+      const parentSubsegment = tracer.getSegment(); // This is the subsegment currently active
+      let subsegment;
+      if (parentSubsegment) {
+        const [_, baseUrl] = request.origin.split("//");
+
+        subsegment = parentSubsegment.addNewSubsegment(baseUrl);
+        tracer.setSegment(subsegment);
+        subsegment.addAttribute("namespace", "remote");
+      }
+      segments.set(request, {
+        subsegment: subsegment!,
+        parentSubsegment: parentSubsegment!,
+      });
+    });
+
+  /**
+   * When the response is received, the response data and headers are added to the subsegment.
+   */
+  diagnosticsChannel
+    .channel("undici:request:headers")
+    .subscribe(async ({ request, response }: any) => {
+      const { subsegment, parentSubsegment } = segments.get(request)!;
+
+      if (parentSubsegment && subsegment) {
+        const [protocol, host] = request.origin.split("//");
+
+        const headers = arrayToObject(response.headers);
+        subsegment.addRemoteRequestData(
+          {
+            ...request,
+            host,
+            agent: {
+              protocol,
+            },
+          },
+          {
+            ...response,
+            headers: headers,
+          }
+        );
+      }
+    });
+
+  /**
+   * The subsegment is closed when the response is finished.
+   */
+  diagnosticsChannel
+    .channel("undici:request:trailers")
+    .subscribe(({ request }: any) => {
+      const { subsegment, parentSubsegment } = segments.get(request)!;
+
+      if (parentSubsegment && subsegment) {
+        subsegment.close();
+        tracer.setSegment(parentSubsegment);
+        segments.delete(request);
+      }
+    });
+}
+
+function arrayToObject(arr: any[]): { [key: string]: any } {
+  const result: { [key: string]: any } = {};
+
+  if (arr.length % 2 !== 0) {
+    throw new Error("Array length should be even to form key-value pairs.");
+  }
+
+  for (let i = 0; i < arr.length; i += 2) {
+    const key = arr[i].toString().toLowerCase();
+    const value = arr[i + 1].toString();
+    result[key] = value;
+  }
+
+  return result;
+}