added a retry for 500 internal service error

.travis.yml

@@ -0,0 +1,9 @@
+language: node_js
+node_js:
+  - "4"
+  - "5"
+  - "6"
+  - "7"
+  - "8"
+  - "9"
+sudo: false

README.md

@@ -47,8 +47,8 @@ Usage:
 mws.Orders.ListOrders({
   MarketplaceId: 'lel',
   MaxResultsPerPage: 10,
-  CreatedAfter: new Date(1,1,2015),
-  CreatedBefore: new Date(1,2,2015)
+  CreatedAfter: new Date(2015, 1, 1),
+  CreatedBefore: new Date(2015, 1, 2)
 })
 .then(({ result, metadata }) => {
   // result

lib/client.js

@@ -123,6 +123,25 @@ class AmazonMwsClient {
      * @return Promise
      */
     call(req, q, meta) {
+
+        const doRetry = (err) => {
+            if (!meta.retry) {
+                throw err;
+            }
+
+            const attempt = meta.attempt + 1;
+
+            if (attempt > meta.max_attempts) {
+                throw err;
+            }
+
+            // simple exponential backoff for dealing with throttling
+            const backoffDuration = Math.min(100 * Math.pow(2, attempt), meta.max_backoff);
+
+            return Promise.delay(backoffDuration)
+                .then(() => this.call(req, q, _.assign({}, meta, { attempt })));
+        };
+
         return this.request(req, q, meta).then((response) => {
             const body = response.body;
 
@@ -166,40 +185,9 @@ class AmazonMwsClient {
                           metadata: _.concat(metadata, nextData.metadata)
                       }));
                 })
-                .catch({ code: 'RequestThrottled' }, (err) => {
-                    if (!meta.retry) {
-                        throw err;
-                    }
-
-                    const attempt = meta.attempt + 1;
-
-                    if (attempt > meta.max_attempts) {
-                        throw err;
-                    }
-
-                    // simple exponential backoff for dealing with throttling
-                    const backoffDuration = Math.min(100 * Math.pow(2, attempt), meta.max_backoff);
-
-                    return Promise.delay(backoffDuration)
-                        .then(() => this.call(req, q, _.assign({}, meta, { attempt })));
-                })
-                .catch({ code: 'QuotaExceeded' }, (err) => {
-                    if (!meta.retry) {
-                        throw err;
-                    }
-
-                    const attempt = meta.attempt + 1;
-
-                    if (attempt > meta.max_attempts) {
-                        throw err;
-                    }
-
-                    // simple exponential backoff for dealing with throttling
-                    const backoffDuration = Math.min(100 * Math.pow(2, attempt), meta.max_backoff);
-
-                    return Promise.delay(backoffDuration)
-                        .then(() => this.call(req, q, _.assign({}, meta, { attempt })));
-                });
+                .catch({ code: 'InternalError' }, doRetry)
+                .catch({ code: 'RequestThrottled' }, doRetry)
+                .catch({ code: 'QuotaExceeded' }, doRetry);
         });
     }