Fixed figures.tasks.backfill_enrollment_data_for_course

Now it looks for stale course enrollments and for each stale course
enrollment found, updates that enrollment's metrics. Prior to this
commit, it was just calling the normal daily enrolment data update
function.

* Updated unit tests

figures/tasks.py

@@ -19,8 +19,10 @@
 from celery.utils.log import get_task_logger
 
 from figures.compat import CourseEnrollment, CourseOverview
+from figures.course import Course
 from figures.helpers import as_course_key, as_date, is_past_date
 from figures.log import log_exec_time
+from figures.models import EnrollmentData
 from figures.sites import get_sites, get_sites_by_id, site_course_ids
 
 from figures.pipeline.backfill import backfill_enrollment_data_for_site
@@ -29,7 +31,10 @@
 from figures.pipeline.mau_pipeline import collect_course_mau
 from figures.pipeline.helpers import DateForCannotBeFutureError
 from figures.pipeline.site_monthly_metrics import fill_last_month as fill_last_smm_month
-from figures.pipeline.enrollment_metrics_next import update_enrollment_data_for_course
+from figures.pipeline.enrollment_metrics_next import (
+    update_enrollment_data_for_course,
+    stale_course_enrollments,
+)
 
 
 logger = get_task_logger(__name__)
@@ -324,15 +329,38 @@ def populate_daily_metrics_next(site_id=None, force_update=False):
 
 @shared_task
 def backfill_enrollment_data_for_course(course_id):
-    """Create or update EnrollmentData records for the course
+    """Update EnrollmentData records for activity before "yesterday"
 
-    This is a simple wrapper to run the enrollment update as a Celery task
+    This task function is to get `EnrollmentData` records up to date. This is
+    needed under at least the following conditions
 
-    We usually run this task through the Figures Django management command,
-    `backfill_figures_enrollment_data`
+    A. Figures is being installed/enabled on an existing Open edX deployment
+    B. The daily pipeline was stopped or failed to run for longer than a day
+
+    Why this function is needed is because it costs too much time to query
+    an enrollment's `StudentModule` record to find the latest date it was
+    modified. For the regular day to day pipeline, Figures can perform a **much**
+    fasater query to find if `StudentModule` records exist for the specific day
+    we gather our daily metrics. This is always the previous calendar day given
+    UTC time. The following function is what updates `EnrollmentData` on the
+    daily job:
+
+    ```
+    figures.pipeline.enrollment_metrics_next.update_enrollment_data_for_course
+    ```
+
+    There is a Figures Django management command to run this task:
+
+    ```
+    backfill_figures_enrollment_data
+    ```
     """
-    # results are a list of (object, created_flag) tuples
-    updated = update_enrollment_data_for_course(course_id)
+    course = Course(course_id)
+    updated = []
+    for enrollment in stale_course_enrollments(course_id):
+        # `update_metrics` results are a (object, created_flag) tuple
+        updated.append(EnrollmentData.objects.update_metrics(course.site, enrollment))
+
     msg = ('figures.tasks.backfill_enrollment_data_for_course "{course_id}".'
            ' Updated {edrec_count} enrollment data records.')
     logger.info(msg.format(course_id=course_id, edrec_count=len(updated)))

tests/tasks/test_backfill_tasks.py

@@ -2,6 +2,7 @@
 """
 from __future__ import absolute_import
 import logging
+import mock
 import pytest
 
 from figures.tasks import backfill_enrollment_data_for_course
@@ -28,7 +29,7 @@ def test_backfill_enrollment_data_for_course_no_update(self, transactional_db,
         # The function returns a list of tuples with (object, created)
         # ed_recs = [(EnrollmentDataFactory(), False) for _ in range(2)]
         caplog.set_level(logging.INFO)
-        func_path = 'figures.tasks.update_enrollment_data_for_course'
+        func_path = 'figures.tasks.stale_course_enrollments'
         monkeypatch.setattr(func_path, lambda course_id: [])
         backfill_enrollment_data_for_course(course_id)
         assert len(caplog.records) == 1
@@ -46,9 +47,11 @@ def test_backfill_enrollment_data_for_course_with_updates(self, transactional_db
         # The function returns a list of tuples with (object, created)
         ed_recs = [(EnrollmentDataFactory(), False) for _ in range(2)]
         caplog.set_level(logging.INFO)
-        func_path = 'figures.tasks.update_enrollment_data_for_course'
-        monkeypatch.setattr(func_path, lambda course_id: ed_recs)
-        backfill_enrollment_data_for_course(course_id)
+        monkeypatch.setattr('figures.tasks.stale_course_enrollments', lambda course_id: ed_recs)
+        with mock.patch('figures.tasks.EnrollmentData') as mock_ed_class:
+            mock_ed_class.return_value.objects.update_metrics.return_value = ed_recs
+            backfill_enrollment_data_for_course(course_id)
+
         assert len(caplog.records) == 1
         assert caplog.records[0].message == self.expected_message_template.format(
             course_id=course_id,