Fixes #17 - Implement Redis Caching (#22)

* Fixes #17 - Implement Redis Caching

Also moves the MySQL volume into Docker

You need the setting REDIS_LOCATION in your .env which the value in
.env.sample works.

To test this do this when it's running, this will set and get from the
cache.

```
docker exec -it clrt_web /code/manage.py shell

Python 3.10.14 (main, Jul  2 2024, 22:12:36) [GCC 12.2.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
(InteractiveConsole)
>>> from django.core.cache import cache; cache.set('test_key', 'test_value', timeout=60);cache.get('test_key')
True
'test_value'
```

* Update backend/settings.py

* Just switch to using default Django Redis

* Adding Redis dependency

* Reverting mysql volume change

.env.sample

@@ -6,6 +6,9 @@ MYSQL_PASSWORD=clrt_pwd
 MYSQL_HOST=clrt_mysql_host
 MYSQL_PORT=3306
 
+# Redis settings
+REDIS_LOCATION=redis://clrt_redis_host:6379
+
 #Django settings
 SECRET_KEY='your-django-key' 
 DJANGO_DEBUG=True

backend/settings.py

@@ -157,16 +157,13 @@
     }
 }
 
-# This is needed to allow the LTI tool to work with the Django cache when running on multiple workers
 CACHES = {
     "default": {
-        "BACKEND": "django_mysql.cache.MySQLCache",
-        "LOCATION": "django_clrt_cache",
-        "KEY_PREFIX": "clrt",
+        "BACKEND": "django.core.cache.backends.redis.RedisCache",
+        "LOCATION": config('REDIS_LOCATION', "redis://clrt_redis_host:6379")
     }
 }
 
-
 # Password validation
 # https://docs.djangoproject.com/en/5.0/ref/settings/#auth-password-validators
 
@@ -214,4 +211,4 @@
 CSP_STYLE_SRC = ["'self'", "https:", "'unsafe-inline'"]
 CSP_FRAME_ANCESTORS = ["'self'"] + [url.strip() for url in config('CSP_FRAME_ANCESTORS', 'canvas-test.it.umich.edu').split(',')] 
 CSP_IMG_SRC = ["'self'", "data:"]
-CSP_FONT_SRC = ["'self'"]
+CSP_FONT_SRC = ["'self'"]

docker-compose.yaml

@@ -12,9 +12,20 @@ services:
     ports:
       - "4306:3306"
     volumes:
-       - ./.data/mysql:/var/lib/mysql
+      - ./.data/mysql:/var/lib/mysql
     container_name: clrt_mysql_host
 
+  redis:
+    image: redis:7
+    command: redis-server --stop-writes-on-bgsave-error no --save ""
+    # This is to simulate an Openshift container with no write permission except to /tmp
+    read_only: true
+    tmpfs:
+        - /tmp
+    volumes:
+        - clrt-redis-data:/data:ro
+    container_name: clrt_redis_host
+
   web:
     build: 
       context: .
@@ -30,4 +41,7 @@ services:
       - mysql
     env_file:
       - .env
-    container_name: clrt_web
+    container_name: clrt_web
+
+volumes:
+  clrt-redis-data:

lti_redirect/migrations/0002_drop_mysql_cache.py

@@ -0,0 +1,13 @@
+from django.db import migrations
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('lti_redirect', '0001_mysql_cache'),  # Ensure this is the correct dependency
+    ]
+
+    operations = [
+        migrations.RunSQL(
+            sql="DROP TABLE IF EXISTS django_clrt_cache;",
+        ),
+    ]

requirements.txt

@@ -8,3 +8,4 @@ django-mysql==4.14.0
 gunicorn==22.0.0
 whitenoise==6.7.0
 debugpy==1.8.2
+redis==5.0.7