Add incremental wait time for subsequent request retries

lib/zendesk-uploader/client-wrapper.js

@@ -7,6 +7,7 @@ const logger = require('../logger');
  * Wrapper class for the `node-zendesk` api client
  * Wraps all requests in the `articles`, `sections`, `categories`, and `accesspolcies` objects in Promises
  * Also wraps requests with a retry functionality that will retry the request if the error response is >= 500 or contains a `retryAfter` property
+ * Subsequent retries without a "retry-after" header will wait twice as long as the last retry before trying the request again
  */
 
 const MAX_RETRIES = 5;
@@ -57,6 +58,7 @@ module.exports = class ZendeskClientWrapper {
 
     _createPromiseRequest() {
         let retries = MAX_RETRIES;
+        let retryNumber = 0;
         // First param is the method to call - subsequent params will be passed to the method
         const args = [].slice.call(arguments);
         const method = args.shift();
@@ -68,7 +70,11 @@ module.exports = class ZendeskClientWrapper {
                     // err.retryAfter is present on all 429 (rate limit has been exceeded) and some 503 errors
                     // err.retryAfter is time to wait in seconds
                     retries--;
-                    let retryAfter = err.retryAfter ? err.retryAfter * 1000 : RETRY_AFTER_DEFAULT;
+                    retryNumber++;
+                    const retryAfter = err.retryAfter
+                        ? err.retryAfter * 1000
+                        // Default retry should wait twice as long as the previous retry
+                        : RETRY_AFTER_DEFAULT * Math.max(Math.pow(2, retryNumber - 1), 1);
                     setTimeout(() => method.apply(this, args), retryAfter);
 
                     logger.warn(`Zendesk request failed. Retrying request after ${retryAfter} milliseconds. ${retries} attempts are remaining.`);

test/unit/zendesk-uploader/client-wrapper.js

@@ -146,6 +146,27 @@ describe('ZendeskClientWrapper', () => {
             });
         });
 
+        it('should retry after twice as long as the last retry for the request when there are subsequent 500 errors', () => {
+            const stub = sandbox.stub(this.zendeskStub.articles, 'create');
+            stub.yields(null, null, {});
+            stub.onFirstCall().yields({statusCode: 503});
+            stub.onSecondCall().yields({statusCode: 503});
+            stub.onThirdCall().yields({statusCode: 503});
+
+            let clock = sandbox.useFakeTimers();
+            let createArticle = this.zendeskClient.articles.create(123, {});
+
+            expect(stub).to.have.been.calledOnce;
+            clock.tick(500);
+            expect(stub).to.have.been.calledTwice;
+            clock.tick(1000);
+            expect(stub).to.have.been.calledThrice;
+            clock.tick(2000);
+            return createArticle.then(() => {
+                expect(stub.callCount).to.be.equal(4);
+            });
+        });
+
         it('should reject the promise if the request fails after 5 retries', () => {
             const stub = sandbox.stub(this.zendeskStub.articles, 'create')
                 .yields({retryAfter: 0.01});