BOTO:S3 handle rate limit exceed and do not expose 500 errors

lms/djangoapps/instructor/tests/test_api.py

@@ -12,6 +12,7 @@ import tempfile
 
 import ddt
 import pytz
+from boto.exception import BotoServerError
 from django.conf import settings
 from django.contrib.auth.models import User
 from django.core import mail
@@ -3020,6 +3021,27 @@ class TestInstructorAPILevelsDataDump(SharedModuleStoreTestCase, LoginEnrollment
             body.endswith('"{user_id}","41","42"\n'.format(user_id=self.students[-1].id))
         )
 
+    @patch('lms.djangoapps.instructor_task.models.logger.error')
+    @patch.dict(settings.GRADES_DOWNLOAD, {'STORAGE_TYPE': 's3'})
+    def test_list_report_downloads_error(self, mock_error):
+        """
+        Tests the Rate-Limit exceeded is handled and does not raise 500 error.
+        """
+        ex_status = 503
+        ex_reason = 'Slow Down'
+        url = reverse('list_report_downloads', kwargs={'course_id': self.course.id.to_deprecated_string()})
+        with patch('openedx.core.storage.S3ReportStorage.listdir', side_effect=BotoServerError(ex_status, ex_reason)):
+            response = self.client.post(url, {})
+        mock_error.assert_called_with(
+            u'Fetching files failed for course: %s, status: %s, reason: %s',
+            self.course.id,
+            ex_status,
+            ex_reason,
+        )
+
+        res_json = json.loads(response.content)
+        self.assertEqual(res_json, {"downloads": []})
+
     def test_list_report_downloads(self):
         url = reverse('list_report_downloads', kwargs={'course_id': self.course.id.to_deprecated_string()})
         with patch('lms.djangoapps.instructor_task.models.DjangoStorageReportStore.links_for') as mock_links_for:

lms/djangoapps/instructor_task/models.py

@@ -15,9 +15,11 @@ ASSUMPTIONS: modules have unique IDs, even across different module_types
 import csv
 import hashlib
 import json
+import logging
 import os.path
 from uuid import uuid4
 
+from boto.exception import BotoServerError
 from django.conf import settings
 from django.contrib.auth.models import User
 from django.core.files.base import ContentFile
@@ -26,6 +28,8 @@ from django.db import models, transaction
 from openedx.core.djangoapps.xmodule_django.models import CourseKeyField
 from openedx.core.storage import get_storage
 
+logger = logging.getLogger(__name__)
+
 # define custom states used by InstructorTask
 QUEUING = 'QUEUING'
 PROGRESS = 'PROGRESS'
@@ -283,6 +287,14 @@ class DjangoStorageReportStore(ReportStore):
             # Django's FileSystemStorage fails with an OSError if the course
             # dir does not exist; other storage types return an empty list.
             return []
+        except BotoServerError as ex:
+            logger.error(
+                u'Fetching files failed for course: %s, status: %s, reason: %s',
+                course_id,
+                ex.status,
+                ex.reason
+            )
+            return []
         files = [(filename, os.path.join(course_dir, filename)) for filename in filenames]
         files.sort(key=lambda f: self.storage.modified_time(f[1]), reverse=True)
         return [