Allow course images to be served from the CDN.

Previously, course images on the student dashboard were always
served from the localhost, even if the CDN was enabled.

openedx/core/djangoapps/content/course_overviews/models.py

@@ -3,6 +3,7 @@ Declaration of CourseOverview model
 """
 import json
 import logging
+from urlparse import urlunparse
 
 from django.db import models, transaction
 from django.db.models.fields import BooleanField, DateTimeField, DecimalField, TextField, FloatField, IntegerField
@@ -17,6 +18,7 @@ from opaque_keys.edx.keys import CourseKey
 from config_models.models import ConfigurationModel
 from lms.djangoapps import django_comment_client
 from openedx.core.djangoapps.models.course_details import CourseDetails
+from static_replace.models import AssetBaseUrlConfig
 from util.date_utils import strftime_localized
 from xmodule import course_metadata_utils
 from xmodule.course_module import CourseDescriptor, DEFAULT_START_DATE
@@ -549,7 +551,28 @@ class CourseOverview(TimeStampedModel):
             urls['small'] = self.image_set.small_url or raw_image_url
             urls['large'] = self.image_set.large_url or raw_image_url
 
-        return urls
+        return self._apply_cdn(urls)
+
+    def _apply_cdn(self, image_urls):
+        """
+        Given a dict of resolutions -> urls, return a copy with CDN applied.
+
+        If CDN does not exist or is disabled, just returns the original. The
+        URLs that we store in CourseOverviewImageSet are all already top level
+        paths, so we don't need to go through the /static remapping magic that
+        happens with other course assets. We just need to add the CDN server if
+        appropriate.
+        """
+        cdn_config = AssetBaseUrlConfig.current()
+        if not cdn_config.enabled:
+            return image_urls
+
+        base_url = cdn_config.base_url
+
+        return {
+            resolution: urlunparse((None, base_url, url, None, None, None))
+            for resolution, url in image_urls.items()
+        }
 
     def __unicode__(self):
         """Represent ourselves with the course key."""

openedx/core/djangoapps/content/course_overviews/tests.py

@@ -17,6 +17,7 @@ from PIL import Image
 from lms.djangoapps.certificates.api import get_active_web_certificate
 from openedx.core.djangoapps.models.course_details import CourseDetails
 from openedx.core.lib.courses import course_image_url
+from static_replace.models import AssetBaseUrlConfig
 from xmodule.assetstore.assetmgr import AssetManager
 from xmodule.contentstore.django import contentstore
 from xmodule.contentstore.content import StaticContent
@@ -644,6 +645,32 @@ class CourseOverviewImageSetTestCase(ModuleStoreTestCase):
         )
 
     @ddt.data(ModuleStoreEnum.Type.mongo, ModuleStoreEnum.Type.split)
+    def test_cdn(self, modulestore_type):
+        """
+        Test that we return CDN prefixed URLs if it is enabled.
+        """
+        with self.store.default_store(modulestore_type):
+            course = CourseFactory.create(default_store=modulestore_type)
+            overview = CourseOverview.get_from_id(course.id)
+
+            # First the behavior when there's no CDN enabled...
+            AssetBaseUrlConfig.objects.all().delete()
+            if modulestore_type == ModuleStoreEnum.Type.mongo:
+                expected_path_start = "/c4x/"
+            elif modulestore_type == ModuleStoreEnum.Type.split:
+                expected_path_start = "/asset-v1:"
+
+            for url in overview.image_urls.values():
+                self.assertTrue(url.startswith(expected_path_start))
+
+            # Now enable the CDN...
+            AssetBaseUrlConfig.objects.create(enabled=True, base_url='fakecdn.edx.org')
+            expected_cdn_url = "//fakecdn.edx.org" + expected_path_start
+
+            for url in overview.image_urls.values():
+                self.assertTrue(url.startswith(expected_cdn_url))
+
+    @ddt.data(ModuleStoreEnum.Type.mongo, ModuleStoreEnum.Type.split)
     def test_error_generating_thumbnails(self, modulestore_type):
         """
         Test a scenario where thumbnails cannot be generated.