feat: configurable maxRetryDelay (#165)

Co-authored-by: Justin Beckwith <beckwith@google.com>

src/index.ts

@@ -70,6 +70,11 @@ export interface RetryConfig {
    * Max permitted Retry-After value (in ms) - rejects if greater. Defaults to 5 mins.
    */
   maxRetryAfter?: number;
+
+  /**
+   * Ceiling for calculated delay (in ms) - delay will not exceed this value.
+   */
+  maxRetryDelay?: number;
 }
 
 export type RaxConfig = {
@@ -258,6 +263,9 @@ function onError(err: AxiosError) {
       } else {
         delay = ((Math.pow(2, retrycount) - 1) / 2) * 1000;
       }
+      if (typeof config.maxRetryDelay === 'number') {
+        delay = Math.min(delay, config.maxRetryDelay);
+      }
     }
     setTimeout(resolve, delay);
   });

test/index.ts

@@ -588,6 +588,33 @@ describe('retry-axios', () => {
     await assert.rejects(axios(cfg));
     assert.strictEqual(scopes[1].isDone(), false);
   });
+
+  it('should use maxRetryDelay', async function () {
+    this.timeout(1000); // Short timeout to trip test if delay longer than expected
+    const scopes = [
+      nock(url).get('/').reply(429, undefined),
+      nock(url).get('/').reply(200, 'toast'),
+    ];
+    interceptorId = rax.attach();
+    const {promise, resolve} = invertedPromise();
+    const clock = sinon.useFakeTimers({
+      shouldAdvanceTime: true, // Otherwise interferes with nock
+    });
+    const axiosPromise = axios({
+      url,
+      raxConfig: {
+        onRetryAttempt: resolve,
+        retryDelay: 10000, // Higher default to ensure maxRetryDelay is used
+        maxRetryDelay: 5000,
+        backoffType: 'exponential',
+      },
+    });
+    await promise;
+    clock.tick(5000); // Advance clock by expected retry delay
+    const res = await axiosPromise;
+    assert.strictEqual(res.data, 'toast');
+    scopes.forEach(s => s.done());
+  });
 });
 
 function invertedPromise() {