fix(ipv6): fetch tries both addresses sometimes and returns Aggregate…

…Error

.gitignore

@@ -62,3 +62,4 @@ tsconfig.build.json
 .prettierrc.js
 .eslintrc.js
 .commitlintrc.json
+vitest.config.ts

__tests__/index.spec.ts

@@ -47,9 +47,9 @@ test('Basic function', async () => {
     server.listen(12345, accept);
   });
 
-  await fetch('http://localhost:12345');
+  await fetch('http://localhost:12345', { keepalive: false });
   expect(config.onRequest).toHaveBeenCalledTimes(1);
-  await fetch('http://localhost:12345', { headers: { 'x-error': '1' } });
+  await fetch('http://localhost:12345', { headers: { 'x-error': '1' }, keepalive: false });
   expect(config.onRequest).toHaveBeenCalledTimes(2);
 
   await new Promise<void>((accept, reject) => {

src/index.ts

@@ -51,6 +51,13 @@ export interface FetchInstrumentationConfig extends InstrumentationConfig {
   }) => void;
 }
 
+function getMessage(error: Error) {
+  if (error instanceof AggregateError) {
+    return error.errors.map((e) => e.message).join(', ');
+  }
+  return error.message;
+}
+
 // Get the content-length from undici response headers.
 // `headers` is an Array of buffers: [k, v, k, v, ...].
 // If the header is not present, or has an invalid value, this returns null.
@@ -215,7 +222,7 @@ export class FetchInstrumentation implements Instrumentation {
       span.recordException(error);
       span.setStatus({
         code: SpanStatusCode.ERROR,
-        message: error.message,
+        message: getMessage(error),
       });
       span.end();
     }