Cache Enrollment state for (user, course) in request cache.

common/djangoapps/student/models.py

@@ -10,7 +10,7 @@ file and check it in at the same time as your model changes. To do that,
 2. ./manage.py lms schemamigration student --auto description_of_your_change
 3. Add the migration file created in edx-platform/common/djangoapps/student/migrations/
 """
-from collections import defaultdict, OrderedDict
+from collections import defaultdict, OrderedDict, namedtuple
 from datetime import datetime, timedelta
 from functools import total_ordering
 import hashlib
@@ -54,6 +54,7 @@ from enrollment.api import _default_course_mode
 import lms.lib.comment_client as cc
 from openedx.core.djangoapps.commerce.utils import ecommerce_api_client, ECOMMERCE_DATE_FORMAT
 from openedx.core.djangoapps.content.course_overviews.models import CourseOverview
+import request_cache
 from openedx.core.djangoapps.site_configuration import helpers as configuration_helpers
 from util.model_utils import emit_field_changed_events, get_changed_fields_dict
 from util.query import use_read_replica_if_available
@@ -974,6 +975,12 @@ class CourseEnrollmentManager(models.Manager):
         )
 
 
+# Named tuple for fields pertaining to the state of
+# CourseEnrollment for a user in a course.  This type
+# is used to cache the state in the request cache.
+CourseEnrollmentState = namedtuple('CourseEnrollmentState', 'mode, is_active')
+
+
 class CourseEnrollment(models.Model):
     """
     Represents a Student's Enrollment record for a single Course. You should
@@ -1120,6 +1127,11 @@ class CourseEnrollment(models.Model):
 
         if activation_changed or mode_changed:
             self.save()
+            self._update_enrollment_in_request_cache(
+                self.user,
+                self.course_id,
+                CourseEnrollmentState(self.mode, self.is_active),
+            )
 
         if activation_changed:
             if self.is_active:
@@ -1389,12 +1401,9 @@ class CourseEnrollment(models.Model):
         """
         if not user.is_authenticated():
             return False
-
-        try:
-            record = cls.objects.get(user=user, course_id=course_key)
-            return record.is_active
-        except cls.DoesNotExist:
-            return False
+        else:
+            enrollment_state = cls._get_enrollment_state(user, course_key)
+            return enrollment_state.is_active or False
 
     @classmethod
     def is_enrolled_by_partial(cls, user, course_id_partial):
@@ -1436,11 +1445,8 @@ class CourseEnrollment(models.Model):
             and is_active is whether the enrollment is active.
         Returns (None, None) if the courseenrollment record does not exist.
         """
-        try:
-            record = cls.objects.get(user=user, course_id=course_id)
-            return (record.mode, record.is_active)
-        except cls.DoesNotExist:
-            return (None, None)
+        enrollment_state = cls._get_enrollment_state(user, course_id)
+        return enrollment_state.mode, enrollment_state.is_active
 
     @classmethod
     def enrollments_for_user(cls, user):
@@ -1593,6 +1599,45 @@ class CourseEnrollment(models.Model):
         """
         return cls.COURSE_ENROLLMENT_CACHE_KEY.format(user_id, unicode(course_key))
 
+    @classmethod
+    def _get_enrollment_state(cls, user, course_key):
+        """
+        Returns the CourseEnrollmentState for the given user
+        and course_key, caching the result for later retrieval.
+        """
+        enrollment_state = cls._get_enrollment_in_request_cache(user, course_key)
+        if not enrollment_state:
+            try:
+                record = cls.objects.get(user=user, course_id=course_key)
+                enrollment_state = CourseEnrollmentState(record.mode, record.is_active)
+            except cls.DoesNotExist:
+                enrollment_state = CourseEnrollmentState(None, None)
+            cls._update_enrollment_in_request_cache(user, course_key, enrollment_state)
+        return enrollment_state
+
+    @classmethod
+    def _get_mode_active_request_cache(cls):
+        """
+        Returns the request-specific cache for CourseEnrollment
+        """
+        return request_cache.get_cache('CourseEnrollment.mode_and_active')
+
+    @classmethod
+    def _get_enrollment_in_request_cache(cls, user, course_key):
+        """
+        Returns the cached value (CourseEnrollmentState) for the user's
+        enrollment in the request cache.  If not cached, returns None.
+        """
+        return cls._get_mode_active_request_cache().get((user.id, course_key))
+
+    @classmethod
+    def _update_enrollment_in_request_cache(cls, user, course_key, enrollment_state):
+        """
+        Updates the cached value for the user's enrollment in the
+        request cache.
+        """
+        cls._get_mode_active_request_cache()[(user.id, course_key)] = enrollment_state
+
 
 @receiver(models.signals.post_save, sender=CourseEnrollment)
 @receiver(models.signals.post_delete, sender=CourseEnrollment)

common/djangoapps/student/tests/tests.py

@@ -6,7 +6,6 @@ from datetime import datetime, timedelta
 import json
 import logging
 import unittest
-from urlparse import urljoin
 
 import ddt
 from django.conf import settings
@@ -30,6 +29,7 @@ from certificates.tests.factories import GeneratedCertificateFactory  # pylint:
 from config_models.models import cache
 from course_modes.models import CourseMode
 from lms.djangoapps.verify_student.models import SoftwareSecurePhotoVerification
+from openedx.core.djangolib.testing.utils import CacheIsolationTestCase
 from openedx.core.djangoapps.programs.models import ProgramsApiConfig
 from openedx.core.djangoapps.programs.tests import factories as programs_factories
 from openedx.core.djangoapps.programs.tests.mixins import ProgramsApiConfigMixin
@@ -589,7 +589,7 @@ class EnrollmentEventTestMixin(EventTestMixin):
         self.mock_tracker.reset_mock()
 
 
-class EnrollInCourseTest(EnrollmentEventTestMixin, TestCase):
+class EnrollInCourseTest(EnrollmentEventTestMixin, CacheIsolationTestCase):
     """Tests enrolling and unenrolling in courses."""
 
     @unittest.skipUnless(settings.ROOT_URLCONF == 'lms.urls', 'Test only valid in lms')