Merge pull request #1967 from edx/feature/cdodge/cap-num-enrollments

Add ability to cap number of enrollments in a course

common/djangoapps/student/models.py

@@ -424,6 +424,28 @@ class CourseEnrollment(models.Model):
 
         return enrollment
 
+    @classmethod
+    def num_enrolled_in(cls, course_id):
+        """
+        Returns the count of active enrollments in a course.
+
+        'course_id' is the course_id to return enrollments
+        """
+        enrollment_number = CourseEnrollment.objects.filter(course_id=course_id, is_active=1).count()
+
+        return enrollment_number
+
+    @classmethod
+    def is_course_full(cls, course):
+        """
+        Returns a boolean value regarding whether a course has already reached it's max enrollment
+        capacity
+        """
+        is_course_full = False
+        if course.max_student_enrollments_allowed is not None:
+            is_course_full = cls.num_enrolled_in(course.location.course_id) >= course.max_student_enrollments_allowed
+        return is_course_full
+
     def update_enrollment(self, mode=None, is_active=None):
         """
         Updates an enrollment for a user in a class.  This includes options

common/djangoapps/student/views.py

@@ -561,6 +561,12 @@ def change_enrollment(request):
         if not has_access(user, course, 'enroll'):
             return HttpResponseBadRequest(_("Enrollment is closed"))
 
+        # see if we have already filled up all allowed enrollments
+        is_course_full = CourseEnrollment.is_course_full(course)
+
+        if is_course_full:
+            return HttpResponseBadRequest(_("Course is full"))
+
         # If this course is available in multiple modes, redirect them to a page
         # where they can choose which mode they want.
         available_modes = CourseMode.modes_for_course(course_id)

common/lib/xmodule/xmodule/course_module.py

@@ -13,7 +13,7 @@ from xmodule.seq_module import SequenceDescriptor, SequenceModule
 from xmodule.graders import grader_from_conf
 import json
 
-from xblock.fields import Scope, List, String, Dict, Boolean
+from xblock.fields import Scope, List, String, Dict, Boolean, Integer
 from .fields import Date
 from xmodule.modulestore.locator import CourseLocator
 from django.utils.timezone import UTC
@@ -384,6 +384,9 @@ class CourseFields(object):
     display_coursenumber = String(help="An optional display string for the course number that will get rendered in the LMS",
                                   scope=Scope.settings)
 
+    max_student_enrollments_allowed = Integer(help="Limit the number of students allowed to enroll in this course.",
+                                              scope=Scope.settings)
+
 class CourseDescriptor(CourseFields, SequenceDescriptor):
     module_class = SequenceModule