✨(session) add redis as session backend

Redis is in our opinion the best practice to record sessions as
it combines the speed of memory with a persistence layer.

config/cms/docker_run_production.py

@@ -157,16 +157,29 @@
 SESSION_COOKIE_HTTPONLY = config(
     "SESSION_COOKIE_HTTPONLY", default=True, formatter=bool
 )
-SESSION_ENGINE = config(
-    "SESSION_ENGINE", default="django.contrib.sessions.backends.cache"
-)
+SESSION_ENGINE = config("SESSION_ENGINE", default="redis_sessions.session")
+
 SESSION_COOKIE_SECURE = config(
     "SESSION_COOKIE_SECURE", default=SESSION_COOKIE_SECURE, formatter=bool
 )
 SESSION_SAVE_EVERY_REQUEST = config(
     "SESSION_SAVE_EVERY_REQUEST", default=SESSION_SAVE_EVERY_REQUEST, formatter=bool
 )
 
+SESSION_REDIS = config(
+    "SESSION_REDIS",
+    default={
+        "host": "redis",
+        "port": 6379,
+        "db": 1,  # db 0 is used for Celery Broker
+        "password": "",
+        "prefix": "session",
+        "socket_timeout": 1,
+        "retry_on_timeout": False,
+    },
+    formatter=json.loads,
+)
+
 # social sharing settings
 SOCIAL_SHARING_SETTINGS = config(
     "SOCIAL_SHARING_SETTINGS", default=SOCIAL_SHARING_SETTINGS, formatter=json.loads

config/lms/docker_run_production.py

@@ -33,8 +33,20 @@
 DEBUG = False
 DEFAULT_TEMPLATE_ENGINE["OPTIONS"]["debug"] = False
 
-SESSION_ENGINE = config(
-    "SESSION_ENGINE", default="django.contrib.sessions.backends.cache"
+SESSION_ENGINE = config("SESSION_ENGINE", default="redis_sessions.session")
+
+SESSION_REDIS = config(
+    "SESSION_REDIS",
+    default={
+        "host": "redis",
+        "port": 6379,
+        "db": 1,  # db 0 is used for Celery Broker
+        "password": "",
+        "prefix": "session",
+        "socket_timeout": 1,
+        "retry_on_timeout": False,
+    },
+    formatter=json.loads,
 )
 
 # IMPORTANT: With this enabled, the server must always be behind a proxy that

docker-compose.yml

@@ -18,6 +18,9 @@ services:
   memcached:
     image: memcached:1.4
 
+  redis:
+      image: redis:4.0
+
   mailcatcher:
     image: sj26/mailcatcher:latest
     ports:
@@ -44,6 +47,7 @@ services:
       - mysql
       - mongodb
       - memcached
+      - redis
     user: ${UID}:${GID}
 
   lms-dev:
@@ -72,6 +76,7 @@ services:
       - mysql
       - mongodb
       - memcached
+      - redis
 
   cms:
     image: edxapp:latest

requirements.txt

@@ -8,3 +8,4 @@ configurable_lti_consumer-xblock==1.0.0-rc.1
 # ==== third-party apps ====
 
 raven==6.9.0
+django-redis-sessions==0.6.1