clear request cache after celery task finishes (TNL-2705)

set max_num_courses_in_cache on modulestore

common/djangoapps/request_cache/tests.py

@@ -1,10 +1,12 @@
 """
 Tests for the request cache.
 """
+from celery.task import task
 from django.conf import settings
 from django.test import TestCase
 
 from request_cache import get_request_or_stub
+from xmodule.modulestore.django import modulestore
 
 
 class TestRequestCache(TestCase):
@@ -13,8 +15,21 @@ class TestRequestCache(TestCase):
     """
 
     def test_get_request_or_stub(self):
-        # Outside the context of the request, we should still get a request
-        # that allows us to build an absolute URI.
+        """
+        Outside the context of the request, we should still get a request
+        that allows us to build an absolute URI.
+        """
         stub = get_request_or_stub()
         expected_url = "http://{site_name}/foobar".format(site_name=settings.SITE_NAME)
         self.assertEqual(stub.build_absolute_uri("foobar"), expected_url)
+
+    @task
+    def _dummy_task(self):
+        """ Create a task that adds stuff to the request cache. """
+        cache = {"course_cache": "blah blah blah"}
+        modulestore().request_cache.data.update(cache)
+
+    def test_clear_cache_celery(self):
+        """ Test that the request cache is cleared after a task is run. """
+        self._dummy_task.apply(args=(self,)).get()
+        self.assertEqual(modulestore().request_cache.data, {})