Release 0.139.3

RELEASE.rst

@@ -1,6 +1,11 @@
 Release Notes
 =============
 
+Version 0.139.3
+---------------
+
+- Make featured homepage courses cache robust against task failures (#3353)
+
 Version 0.139.2 (Released March 04, 2026)
 ---------------
 

cms/api.py

@@ -23,7 +23,11 @@
 from wagtail.rich_text import RichText
 
 from cms import models as cms_models
-from cms.constants import CERTIFICATE_INDEX_SLUG, INSTRUCTOR_INDEX_SLUG
+from cms.constants import (
+    CERTIFICATE_INDEX_SLUG,
+    FEATURED_ITEMS_CACHE_KEY,
+    INSTRUCTOR_INDEX_SLUG,
+)
 from cms.exceptions import WagtailSpecificPageError
 from cms.models import Page
 from courses.models import Course, Program
@@ -477,9 +481,6 @@ def create_featured_items():
     Used only by cron task or management command.
     """
     redis_cache = caches["redis"]
-    cache_key = "CMS_homepage_featured_courses"
-
-    redis_cache.delete(cache_key)
 
     now = now_in_utc()
     end_of_day = now + timedelta(days=1)
@@ -491,7 +492,6 @@ def create_featured_items():
     )
 
     if not valid_course_ids:
-        redis_cache.set(cache_key, [])
         return []
 
     enrollable_courses_qs = Course.objects.select_related("page").filter(
@@ -504,7 +504,6 @@ def create_featured_items():
     )
 
     if not enrollable_courseruns.exists():
-        redis_cache.set(cache_key, [])
         return []
 
     self_paced_runs = []
@@ -537,7 +536,6 @@ def create_featured_items():
     all_course_ids = self_paced_course_ids + future_course_ids + started_course_ids
 
     if not all_course_ids:
-        redis_cache.set(cache_key, [])
         return []
 
     ordering = Case(
@@ -546,7 +544,8 @@ def create_featured_items():
     )
 
     # Store only course IDs to avoid pickling issues and ensure fresh data on retrieval
-    redis_cache.set(cache_key, all_course_ids)
+    # Use timeout=None so the cache never auto-expires; stale data is better than no data.
+    redis_cache.set(FEATURED_ITEMS_CACHE_KEY, all_course_ids, timeout=None)
 
     return list(
         Course.objects.filter(id__in=all_course_ids)

cms/api_test.py

@@ -21,6 +21,7 @@
     get_home_page,
     get_wagtail_img_src,
 )
+from cms.constants import FEATURED_ITEMS_CACHE_KEY
 from cms.exceptions import WagtailSpecificPageError
 from cms.factories import CoursePageFactory, HomePageFactory, ProgramPageFactory
 from cms.models import (
@@ -376,22 +377,38 @@ def test_create_featured_items():
 
 @pytest.mark.django_db
 def test_create_featured_items_no_courses():
-    """Test create_featured_items with no courses at all"""
+    """Test create_featured_items with no courses leaves stale cache intact"""
+    redis_cache = caches["redis"]
+    stale_value = [999]
+    redis_cache.set("CMS_homepage_featured_courses", stale_value)
+
+    result = create_featured_items()
+    cache_value = redis_cache.get("CMS_homepage_featured_courses")
+
+    # Returns empty list but does NOT wipe stale cache data
+    assert result == []
+    assert cache_value == stale_value
+
+
+@pytest.mark.django_db
+def test_create_featured_items_no_courses_no_prior_cache():
+    """Test create_featured_items with no courses and no prior cache entry"""
     redis_cache = caches["redis"]
     redis_cache.delete("CMS_homepage_featured_courses")
 
     result = create_featured_items()
     cache_value = redis_cache.get("CMS_homepage_featured_courses")
 
     assert result == []
-    assert cache_value == []
+    assert cache_value is None
 
 
 @pytest.mark.django_db
 def test_create_featured_items_no_enrollable_courses():
-    """Test create_featured_items with courses but no enrollable runs"""
+    """Test create_featured_items with courses but no enrollable runs leaves stale cache intact"""
     redis_cache = caches["redis"]
-    redis_cache.delete("CMS_homepage_featured_courses")
+    stale_value = [888]
+    redis_cache.set("CMS_homepage_featured_courses", stale_value)
 
     # Create course with no enrollable runs
     course = CourseFactory.create(page=None, live=True)
@@ -401,8 +418,9 @@ def test_create_featured_items_no_enrollable_courses():
     result = create_featured_items()
     cache_value = redis_cache.get("CMS_homepage_featured_courses")
 
+    # Returns empty list but does NOT wipe stale cache data
     assert result == []
-    assert cache_value == []
+    assert cache_value == stale_value
 
 
 @pytest.mark.django_db
@@ -557,10 +575,10 @@ def test_create_featured_items_mixed_course_types():
 
 
 @pytest.mark.django_db
-def test_create_featured_items_cache_expiration():
-    """Test that cache is set with correct expiration time"""
+def test_create_featured_items_cache_no_expiry():
+    """Test that cache is set with timeout=None so it never auto-expires"""
     redis_cache = caches["redis"]
-    redis_cache.delete("CMS_homepage_featured_courses")
+    redis_cache.delete(FEATURED_ITEMS_CACHE_KEY)
 
     # Create a simple course to have something to cache
     course = CourseFactory.create(page=None, live=True)
@@ -576,10 +594,20 @@ def test_create_featured_items_cache_expiration():
 
     create_featured_items()
 
-    # Verify cache is set
-    cache_value = redis_cache.get("CMS_homepage_featured_courses")
+    # Verify cache is still set and correct
+    cache_value = redis_cache.get(FEATURED_ITEMS_CACHE_KEY)
     assert cache_value is not None
     assert len(cache_value) == 1
 
-    # Note: TTL testing would require mocking or actual time measurement
-    # which might be flaky, so we just verify the cache is set
+    redis_client = redis_cache.client.get_client()
+    # redis returns -1 for a key being present with no expiry
+    # see https://redis.io/docs/latest/commands/ttl/
+    # note that the actual key in redis is prefixed with ":1:"
+    # we use the raw client, not the one provided by redis_django,
+    # because the latter rewrites the return values
+    ttl = redis_client.ttl(f":1:{FEATURED_ITEMS_CACHE_KEY}")
+    assert ttl == -1, (
+        f"Key `{FEATURED_ITEMS_CACHE_KEY}` is missing"
+        if ttl == -2
+        else f"Unexpected ttl value `{ttl}` for `{FEATURED_ITEMS_CACHE_KEY}`"
+    )

cms/constants.py

@@ -10,3 +10,5 @@
 INSTRUCTOR_INDEX_SLUG = "instructors"
 
 ONE_MINUTE = 60
+
+FEATURED_ITEMS_CACHE_KEY = "CMS_homepage_featured_courses"

main/settings.py

@@ -37,7 +37,7 @@
 from main.sentry import init_sentry
 from openapi.settings_spectacular import open_spectacular_settings
 
-VERSION = "0.139.2"
+VERSION = "0.139.3"
 
 log = logging.getLogger()