refactor: fastFailMetadataRequest to use Promise.any

src/index.ts

@@ -191,41 +191,14 @@ async function fastFailMetadataRequest<T>(
   // 2. we can't just check the IP, which is tarpitted and slow to respond
   //    on a user's local machine.
   //
-  // Additional logic has been added to make sure that we don't create an
-  // unhandled rejection in scenarios where a failure happens sometime
-  // after a success.
+  // Returns first resolved promise or if all promises get rejected we return an AggregateError.
   //
   // Note, however, if a failure happens prior to a success, a rejection should
   // occur, this is for folks running locally.
   //
-  let responded = false;
-  const r1: Promise<GaxiosResponse> = request<T>(options)
-    .then(res => {
-      responded = true;
-      return res;
-    })
-    .catch(err => {
-      if (responded) {
-        return r2;
-      } else {
-        responded = true;
-        throw err;
-      }
-    });
-  const r2: Promise<GaxiosResponse> = request<T>(secondaryOptions)
-    .then(res => {
-      responded = true;
-      return res;
-    })
-    .catch(err => {
-      if (responded) {
-        return r1;
-      } else {
-        responded = true;
-        throw err;
-      }
-    });
-  return Promise.race([r1, r2]);
+  const r1: Promise<GaxiosResponse> = request<T>(options);
+  const r2: Promise<GaxiosResponse> = request<T>(secondaryOptions);
+  return Promise.any([r1, r2]);
 }
 
 /**

test/index.test.ts

@@ -413,7 +413,7 @@ describe('unit test', () => {
       err = _err;
     };
 
-    const secondary = secondaryHostRequest(500);
+    const secondary = secondaryHostRequest(500, 'ENOTFOUND');
     const primary = nock(HOST)
       .get(`${PATH}/${TYPE}`)
       .replyWithError({code: 'ENOTFOUND'});
@@ -422,7 +422,7 @@ describe('unit test', () => {
     primary.done();
     console.info = info;
     delete process.env.DEBUG_AUTH;
-    assert.strictEqual(/failed, reason/.test(err!.message), true);
+    assert.strictEqual(/All promises were rejected/.test(err!.message), true);
   });
 
   [
@@ -433,8 +433,8 @@ describe('unit test', () => {
     'ENOTFOUND',
     'ECONNREFUSED',
   ].forEach(errorCode => {
-    it(`should fail fast on isAvailable if ${errorCode} is returned`, async () => {
-      const secondary = secondaryHostRequest(500);
+    it(`should fail on isAvailable if ${errorCode} is returned for primary and secondary requests`, async () => {
+      const secondary = secondaryHostRequest(500, errorCode);
       const primary = nock(HOST)
         .get(`${PATH}/${TYPE}`)
         .replyWithError({code: errorCode});
@@ -445,13 +445,13 @@ describe('unit test', () => {
     });
   });
 
-  it('should fail fast on isAvailable if 404 status code is returned', async () => {
+  it('should return first successful response', async () => {
     const secondary = secondaryHostRequest(500);
     const primary = nock(HOST).get(`${PATH}/${TYPE}`).reply(404);
     const isGCE = await gcp.isAvailable();
     await secondary;
     primary.done();
-    assert.strictEqual(false, isGCE);
+    assert.strictEqual(true, isGCE);
   });
 
   it('should fail fast with GCE_METADATA_HOST 404 on isAvailable', async () => {
@@ -606,8 +606,8 @@ describe('unit test', () => {
   it('resets cache when resetIsAvailableCache() is called', async () => {
     // we will attempt to hit the secondary and primary server twice,
     // mock accordingly.
-    const secondary = secondaryHostRequest(250);
-    const secondary2 = secondaryHostRequest(500);
+    const secondary = secondaryHostRequest(250, 'ENOENT');
+    const secondary2 = secondaryHostRequest(500, 'ENOENT');
     const primary = nock(HOST)
       .get(`${PATH}/${TYPE}`)
       .reply(200, {}, HEADERS)

tsconfig.json

@@ -1,7 +1,7 @@
 {
   "extends": "./node_modules/gts/tsconfig-google.json",
   "compilerOptions": {
-    "lib": ["es2018", "dom"],
+    "lib": ["es2021", "dom"],
     "rootDir": ".",
     "outDir": "build"
   },