Merge pull request #2 from CoSchedule/jfm-add_request_retry_feature

[CHORE] Add ability to internally retry /oauth/token calls.

auth.js

@@ -1,4 +1,14 @@
-const request = require('request-promise');
+const { requestWithRetries, isRequestError, isStatusCodeError } = require('./requestPromiseUtils');
+
+const shouldRetry = (err, nextTryCount) => {
+  if (nextTryCount > 5) {
+    return false;
+  }
+
+  return isRequestError(err) || (isStatusCodeError(err) && (err.statusCode === 403));
+};
+
+const computeRetryDelay = (err, nextTryCount) => (Math.round(Math.random() * 100) + (nextTryCount * 750));
 
 module.exports = (zuoraClient) => {
   let accessToken;
@@ -22,7 +32,10 @@ module.exports = (zuoraClient) => {
       json: true,
     };
 
-    const response = await request(options);
+    const response = await requestWithRetries(options, shouldRetry, computeRetryDelay);
+    if (!response) {
+      throw new Error('ZuoraJS: Auth: Empty Response');
+    }
 
     accessToken = response.access_token;
     renewalTime = Date.now() + ((response.expires_in * 1000) - 60000);

requestPromiseUtils.js

@@ -0,0 +1,34 @@
+const requestPromise = require('request-promise');
+const requestPromiseErrors = require('request-promise/errors');
+
+const requestWithRetries = async (requestOptions, shouldRetry, computeRetryDelay) => {
+  const makeRequest = async (tryCount) => {
+    let response;
+    try {
+      response = await requestPromise(requestOptions);
+    } catch (err) {
+      if (!shouldRetry || !shouldRetry(err, tryCount)) {
+        throw err;
+      }
+
+      const nextTryCount = tryCount + 1;
+      const retryDelay = await ((computeRetryDelay && computeRetryDelay(err, nextTryCount)) || 1000);
+      await new Promise((resolve) => setTimeout(resolve, retryDelay));
+
+      response = makeRequest(nextTryCount);
+    }
+
+    return response;
+  };
+
+  return makeRequest(1);
+};
+
+const isRequestError = (err) => (err instanceof requestPromiseErrors.RequestError);
+const isStatusCodeError = (err) => (err instanceof requestPromiseErrors.StatusCodeError);
+
+module.exports = {
+  requestWithRetries,
+  isRequestError,
+  isStatusCodeError,
+};