From 896bc1c8595705e06c7ceba10cf2bd7e6b6c63b7 Mon Sep 17 00:00:00 2001
From: stephensanchez <steve@edx.org>
Date: Thu, 22 Jan 2015 17:05:57 +0000
Subject: [PATCH] Adding caching to the course details endpoint for the
 Enrollment API.

---
 common/djangoapps/enrollment/api.py           | 27 ++++++++++++++++++-
 .../djangoapps/enrollment/tests/test_api.py   | 19 ++++++++++++-
 lms/envs/aws.py                               |  3 +++
 lms/envs/common.py                            |  3 +++
 4 files changed, 50 insertions(+), 2 deletions(-)

diff --git a/common/djangoapps/enrollment/api.py b/common/djangoapps/enrollment/api.py
index 1290992663..7fd5599cac 100644
--- a/common/djangoapps/enrollment/api.py
+++ b/common/djangoapps/enrollment/api.py
@@ -5,6 +5,7 @@ course level, such as available course modes.
 """
 from django.utils import importlib
 import logging
+from django.core.cache import cache
 from django.conf import settings
 from enrollment import errors
 
@@ -250,7 +251,31 @@ def get_course_enrollment_details(course_id):
         }
 
     """
-    return _data_api().get_course_enrollment_info(course_id)
+    cache_key = u"enrollment.course.details.{course_id}".format(course_id=course_id)
+
+    cached_enrollment_data = None
+    try:
+        cached_enrollment_data = cache.get(cache_key)
+    except Exception:
+        # The cache backend could raise an exception (for example, memcache keys that contain spaces)
+        log.exception(u"Error occurred while retrieving course enrollment details from the cache")
+
+    if cached_enrollment_data:
+        log.info(u"Get enrollment data for course %s (cached)", course_id)
+        return cached_enrollment_data
+
+    course_enrollment_details = _data_api().get_course_enrollment_info(course_id)
+
+    try:
+        cache_time_out = getattr(settings, 'ENROLLMENT_COURSE_DETAILS_CACHE_TIMEOUT', 60)
+        cache.set(cache_key, course_enrollment_details, cache_time_out)
+    except Exception:
+        # Catch any unexpected errors during caching.
+        log.exception(u"Error occurred while caching course enrollment details for course %s", course_id)
+        raise errors.CourseEnrollmentError(u"An unexpected error occurred while retrieving course enrollment details.")
+
+    log.info(u"Get enrollment data for course %s", course_id)
+    return course_enrollment_details
 
 
 def _validate_course_mode(course_id, mode):
diff --git a/common/djangoapps/enrollment/tests/test_api.py b/common/djangoapps/enrollment/tests/test_api.py
index f6b80994b6..c165a5d627 100644
--- a/common/djangoapps/enrollment/tests/test_api.py
+++ b/common/djangoapps/enrollment/tests/test_api.py
@@ -2,6 +2,7 @@
 Tests for student enrollment.
 """
 import ddt
+from django.core.cache import cache
 from nose.tools import raises
 import unittest
 from django.test import TestCase
@@ -24,6 +25,7 @@ class EnrollmentTest(TestCase):
 
     def setUp(self):
         fake_data_api.reset()
+        cache.clear()
 
     @ddt.data(
         # Default (no course modes in the database)
@@ -125,7 +127,7 @@ class EnrollmentTest(TestCase):
             )
 
     def test_update_enrollment(self):
-        # Add a fake course enrollment information to the fake data API
+        # Add fake course enrollment information to the fake data API
         fake_data_api.add_course(self.COURSE_ID, course_modes=['honor', 'verified', 'audit'])
         # Enroll in the course and verify the URL we get sent to
         result = api.add_enrollment(self.USERNAME, self.COURSE_ID, mode='audit')
@@ -150,3 +152,18 @@ class EnrollmentTest(TestCase):
     def test_data_api_config_error(self):
         # Enroll in the course and verify the URL we get sent to
         api.add_enrollment(self.USERNAME, self.COURSE_ID, mode='audit')
+
+    def test_caching(self):
+        # Add fake course enrollment information to the fake data API
+        fake_data_api.add_course(self.COURSE_ID, course_modes=['honor', 'verified', 'audit'])
+
+        # Hit the fake data API.
+        details = api.get_course_enrollment_details(self.COURSE_ID)
+
+        # Reset the fake data API, should rely on the cache.
+        fake_data_api.reset()
+        cached_details = api.get_course_enrollment_details(self.COURSE_ID)
+
+        # The data matches
+        self.assertEqual(len(details['course_modes']), 3)
+        self.assertEqual(details, cached_details)
diff --git a/lms/envs/aws.py b/lms/envs/aws.py
index a33359ad29..e0f117246d 100644
--- a/lms/envs/aws.py
+++ b/lms/envs/aws.py
@@ -484,6 +484,9 @@ INVOICE_PAYMENT_INSTRUCTIONS = ENV_TOKENS.get('INVOICE_PAYMENT_INSTRUCTIONS', IN
 API_DATE_FORMAT = '%Y-%m-%d'
 API_DATE_FORMAT = ENV_TOKENS.get('API_DATE_FORMAT', API_DATE_FORMAT)
 
+# Enrollment API Cache Timeout
+ENROLLMENT_COURSE_DETAILS_CACHE_TIMEOUT = ENV_TOKENS.get('ENROLLMENT_COURSE_DETAILS_CACHE_TIMEOUT', 60)
+
 # PDF RECEIPT/INVOICE OVERRIDES
 PDF_RECEIPT_TAX_ID = ENV_TOKENS.get('PDF_RECEIPT_TAX_ID', PDF_RECEIPT_TAX_ID)
 PDF_RECEIPT_FOOTER_TEXT = ENV_TOKENS.get('PDF_RECEIPT_FOOTER_TEXT', PDF_RECEIPT_FOOTER_TEXT)
diff --git a/lms/envs/common.py b/lms/envs/common.py
index 1b015000db..f609758535 100644
--- a/lms/envs/common.py
+++ b/lms/envs/common.py
@@ -1990,6 +1990,9 @@ COURSE_ABOUT_VISIBILITY_PERMISSION = 'see_exists'
 #date format the api will be formatting the datetime values
 API_DATE_FORMAT = '%Y-%m-%d'
 
+# Enrollment API Cache Timeout
+ENROLLMENT_COURSE_DETAILS_CACHE_TIMEOUT = 60
+
 # for Student Notes we would like to avoid too frequent token refreshes (default is 30 seconds)
 if FEATURES['ENABLE_EDXNOTES']:
     OAUTH_ID_TOKEN_EXPIRATION = 60 * 60