feat: drop cache on course enrollments change

lms/djangoapps/grades/rest_api/v1/gradebook_views.py

@@ -670,7 +670,7 @@ def get(self, request, course_key):  # lint-amnesty, pylint: disable=too-many-st
             serializer = StudentGradebookEntrySerializer(entries, many=True)
             return self.get_paginated_response(serializer.data, **users_counts)
 
-    def _get_user_count(self, query_args, cache_time=600, annotations=None):
+    def _get_user_count(self, course_key, query_args, cache_time=600, annotations=None):
         """
         Return the user count for the given query arguments to CourseEnrollment.
 
@@ -681,7 +681,7 @@ def _get_user_count(self, query_args, cache_time=600, annotations=None):
             queryset = queryset.annotate(**annotations)
         queryset = queryset.filter(*query_args)
 
-        cache_key = 'usercount.%s' % queryset.query
+        cache_key = 'usercount.{course_key}.{queryset.query}'
         user_count = cache.get(cache_key, None)
         if user_count is None:
             user_count = queryset.count()
@@ -710,15 +710,15 @@ def _get_users_counts(self, course_key, course_enrollment_filters, annotations=N
             Q(course_id=course_key) & Q(is_active=True)
         ]
 
-        total_users_count = self._get_user_count(filter_args)
+        total_users_count = self._get_user_count(course_key, filter_args)
 
         filter_args.extend(course_enrollment_filters or [])
 
         # if course_enrollment_filters is empty, then the number of filtered users will equal the total number of users
         filtered_users_count = (
             total_users_count
             if not course_enrollment_filters
-            else self._get_user_count(filter_args, annotations=annotations)
+            else self._get_user_count(course_key, filter_args, annotations=annotations)
         )
 
         return {

lms/djangoapps/grades/signals/handlers.py

@@ -5,15 +5,18 @@
 
 from contextlib import contextmanager
 from logging import getLogger
+from urllib.parse import unquote
 
+from django.conf import settings
+from django.core.cache import cache
 from django.dispatch import receiver
 from opaque_keys.edx.keys import LearningContextKey
 from openedx_events.learning.signals import EXAM_ATTEMPT_REJECTED, EXAM_ATTEMPT_VERIFIED
 from submissions.models import score_reset, score_set
 from xblock.scorable import ScorableXBlockMixin, Score
 
 from common.djangoapps.student.models import user_by_anonymous_id
-from common.djangoapps.student.signals import ENROLLMENT_TRACK_UPDATED
+from common.djangoapps.student.signals import ENROLL_STATUS_CHANGE, ENROLLMENT_TRACK_UPDATED
 from common.djangoapps.track.event_transaction_utils import get_event_transaction_id, get_event_transaction_type
 from common.djangoapps.util.date_utils import to_timestamp
 from lms.djangoapps.courseware.model_data import get_score, set_score
@@ -347,3 +350,38 @@ def exam_attempt_rejected_event_handler(sender, signal, **kwargs):  # pylint: di
         overrider=None,
         comment=None,
     )
+
+@receiver(ENROLL_STATUS_CHANGE)
+def invalidate_usercount_in_course_cache(sender, signal, **kwargs):  # pylint: disable=unused-argument
+    """
+    Invalidate the cache of get_user_count utility on CourseEnrollment status change.
+    """
+    event_data = kwargs.get('exam_attempt')
+    course_key = event_data.course_id   
+
+    cache_key_prefix = f"usercount.{course_key}"
+    cache_keys = get_cache_keys(cache_key_prefix)
+    cache.delete_many(cache_keys)
+
+
+def get_cache_keys(cache_key_prefix):
+    """
+    Get all cache keys for the given cache key prefix.
+    LocMemCache does not have a keys method, so we need to iterate over the cache
+    and manually filter out the keys that match the given prefix.
+    """
+    cache_backend = settings.CACHES['default']['BACKEND']
+    if cache_backend == 'django_redis.cache.RedisCache':
+        yield cache.iter_keys(f"{cache_key_prefix}*")
+    elif cache_backend == 'django.core.cache.backends.locmem.LocMemCache':
+        for key in cache._cache.keys():  # pylint: disable=protected-access
+            try:
+                decoded_key = unquote(key.split(':', 2)[-1], encoding='utf-8')
+            except IndexError:
+                continue
+
+            if decoded_key.startswith(cache_key_prefix):
+                yield decoded_key
+    else:
+        log.error(f"Unsupported cache backend: {cache_backend}")
+        yield