Add redis service to improve LTI launch performance (tl-its-umich-e…

…du#277)

* Add some experimental refactoring, cleanup, and settings

* Tweak error throwing so message is shown to user; log LtiException

* Modify error message extraction, construction

* Update import syntax, order

* Remove unused import, one-line other imports

* Add newline

* Add maybe functional redis implementation?

* Simplify redis setup; add password auth

* Upgrade to latest django-redis

* Remove django-mysql cache configs

* Apply suggestions from code review

Update REDIS to support full URL and document values

---------

Co-authored-by: Code Hugger (Matthew Jones) <[email protected]>

.env.sample

@@ -61,6 +61,13 @@ ALLOWED_HOSTS=.ngrok.io,.localhost,127.0.0.1
 # Database Password
 # DB_PASSWORD=cae_pw
 
+##### Redis
+
+# Redis Password, default is blank
+REDIS_PASS=
+# Redis URL, full url of redis server and database number, has a default in the code
+# REDIS_URL= redis://redis:6379/1
+
 ##### Gunicorn server options
 # Number of workers to start
 # GUNICORN_WORKERS=4

.gitignore

@@ -4,6 +4,7 @@ webpack-stats.json
 # MySQL data files
 .data
 ngrok.yml
+redis.conf
 
 # Temp files
 *.swp

backend/canvas_app_explorer/lti1p3.py

@@ -12,19 +12,29 @@
 from django.urls import reverse
 from django.views.decorators.csrf import csrf_exempt
 from django.views.decorators.http import require_POST
-from pylti1p3.contrib.django import DjangoOIDCLogin, DjangoMessageLaunch, \
-    DjangoCacheDataStorage, DjangoDbToolConf
+from pylti1p3.contrib.django import (
+    DjangoCacheDataStorage, DjangoDbToolConf, DjangoMessageLaunch, DjangoOIDCLogin
+)
+from pylti1p3.exception import LtiException
 
 from .canvas_roles import STAFF_COURSE_ROLES
 
+
 logger = logging.getLogger(__name__)
 
+COURSE_MEMBERSHIP = 'http://purl.imsglobal.org/vocab/lis/v2/membership'
+TOOL_CONF = DjangoDbToolConf()
 
+CacheConfig = namedtuple('CacheConfig', ['launch_data_storage', 'cache_lifetime'])
 
-COURSE_MEMBERSHIP = 'http://purl.imsglobal.org/vocab/lis/v2/membership'
-DUMMY_CACHE = 'DummyCache'
 
-TOOL_CONF = DjangoDbToolConf()
+def extract_error_message(error: Exception) -> Union[str, None]:
+    """
+    Check Exception for a string message as the first position argument.
+    """
+    if len(error.args) >= 1 and isinstance(error.args[0], str):
+        return error.args[0]
+    return None
 
 # Custom LTI variable keys
 USERNAME_KEY = 'user_username'
@@ -111,17 +121,14 @@ def generate_config_json(request: HttpRequest) -> \
     return HttpResponse(config_json, content_type='application/json')
 
 
-def get_cache_config():
-    CacheConfig = namedtuple('CacheConfig', ['is_dummy_cache', 'launch_data_storage', 'cache_lifetime'])
-    is_dummy_cache = DUMMY_CACHE in settings.DB_CACHE_CONFIGS['BACKEND']
-    launch_data_storage = DjangoCacheDataStorage(cache_name='default') if not is_dummy_cache else None
+def get_cache_config() -> CacheConfig:
+    launch_data_storage = DjangoCacheDataStorage()
     cache_ttl = settings.DB_CACHE_CONFIGS['CACHE_TTL']
     cache_lifetime = cache_ttl if cache_ttl else 7200
-    return CacheConfig(is_dummy_cache, launch_data_storage, cache_lifetime)
+    return CacheConfig(launch_data_storage, cache_lifetime)
 
 
-def create_user_in_django(request: HttpRequest, message_launch: ExtendedDjangoMessageLaunch):
-    launch_data = message_launch.get_launch_data()
+def create_user_in_django(request: HttpRequest, launch_data: Dict[str, Any]):
     logger.debug(f'lti launch data {launch_data}')
     custom_params = launch_data['https://purl.imsglobal.org/spec/lti/claim/custom']
     logger.debug(f'lti_custom_param {custom_params}')
@@ -191,34 +198,44 @@ def create_user_in_django(request: HttpRequest, message_launch: ExtendedDjangoMe
 
 
 @csrf_exempt
-def login(request):
+def login(request: HttpRequest):
+    cache_config = get_cache_config()
     target_link_uri = request.POST.get('target_link_uri', request.GET.get('target_link_uri'))
     if not target_link_uri:
         error_message = 'LTI Login failed due to missing "target_link_uri" param'
         return lti_error(error_message)
-    CacheConfig = get_cache_config()
-    oidc_login = DjangoOIDCLogin(request, TOOL_CONF, launch_data_storage=CacheConfig.launch_data_storage)
+    oidc_login = DjangoOIDCLogin(request, TOOL_CONF, launch_data_storage=cache_config.launch_data_storage)
     return oidc_login.enable_check_cookies().redirect(target_link_uri)
 
 
 @require_POST
 @csrf_exempt
-def launch(request):
-    CacheConfig = get_cache_config()
-    message_launch = ExtendedDjangoMessageLaunch(request, TOOL_CONF, launch_data_storage=CacheConfig.launch_data_storage)
-    if not CacheConfig.is_dummy_cache:
-        # fetch platform's public key from cache instead of calling the API will speed up the launch process
-        message_launch.set_public_key_caching(CacheConfig.launch_data_storage,
-                                              cache_lifetime=CacheConfig.cache_lifetime)
-    else:
-        logger.info('DummyCache is set up, recommended atleast to us Mysql DB cache for LTI advantage services')
+def launch(request: HttpRequest):
+    cache_config = get_cache_config()
+    message_launch = ExtendedDjangoMessageLaunch(request, TOOL_CONF, launch_data_storage=cache_config.launch_data_storage)
+    message_launch.set_public_key_caching(cache_config.launch_data_storage, cache_config.cache_lifetime)
+
+    try:
+        launch_data: Dict[str, Any] = message_launch.get_launch_data()
+    except LtiException as lti_exception:
+        logger.error(lti_exception)
+        message = f'LTI launch error occurred. Please try launching the tool again.'
+        error_message = extract_error_message(lti_exception)
+        if error_message:
+            message += f' Error: {error_message}.'
+        response = HttpResponse(message)
+        response.status_code = 401
+        return response
 
     # TODO: Implement custom AUTHENTICATION_BACKEND rather than using this one
     try:
-        create_user_in_django(request, message_launch)
+        create_user_in_django(request, launch_data)
     except PermissionDenied as e:
-        message = f': {e.args[0]}' if len(e.args) >= 1 else ''
-        return HttpResponseForbidden('Permission denied' + message)
+        message = 'Permission denied.'
+        error_message = extract_error_message(e)
+        if error_message:
+            message += ' ' + error_message
+        return HttpResponseForbidden(message)
 
     url = reverse('home')
     return redirect(url)

backend/settings.py

@@ -47,7 +47,6 @@
     'django.contrib.contenttypes',
     'django.contrib.sessions',
     'django.contrib.messages',
-    'django_mysql',
     'webpack_loader',
     'rest_framework',
     'pylti1p3.contrib.django.lti1p3_tool_config',
@@ -154,12 +153,19 @@
 # So request works over the proxy
 SECURE_PROXY_SSL_HEADER = ('HTTP_X_FORWARDED_PROTO', 'https')
 
-DB_CACHE_CONFIGS = os.getenv('DB_CACHE_CONFIGS',
-                           {'CACHE_TTL': 600, 'BACKEND': 'django_mysql.cache.MySQLCache',
-                            'LOCATION': 'canvas_app_explorer_cache',
-                            'CACHE_KEY_PREFIX': 'app_explorer',
-                            'CACHE_OPTIONS': {'COMPRESS_MIN_LENGTH': 5000, 'COMPRESS_LEVEL': 6}
-                            })
+DB_CACHE_CONFIGS = os.getenv(
+    'DB_CACHE_CONFIGS',
+    {
+        'CACHE_TTL': 600,
+        'BACKEND': 'django_redis.cache.RedisCache',
+        'LOCATION': os.getenv('REDIS_URL', 'redis://redis:6379/1'),
+        'CACHE_KEY_PREFIX': 'app_explorer',
+        'CACHE_OPTIONS': {
+            'CLIENT_CLASS': 'django_redis.client.DefaultClient',
+            'PASSWORD': os.getenv('REDIS_PASS')
+        }
+    }
+)
 
 CACHES = {
     'default': {
@@ -171,6 +177,8 @@
     }
 }
 
+SESSION_ENGINE = 'django.contrib.sessions.backends.cache'
+
 LOGGING = {
     'version': 1,
     'disable_existing_loggers': False,

docker-compose.yml

@@ -35,3 +35,8 @@ services:
       - .env
     environment:
       - DEBUG=True
+  redis:
+    image: redis:7
+    volumes:
+      - ./redis.conf:/usr/local/etc/redis/redis.conf
+    command: [ "redis-server", "--include /usr/local/etc/redis/redis.conf" ]

redis.conf.sample

@@ -0,0 +1,2 @@
+loglevel debug
+requirepass 'some password here'

requirements.txt

@@ -6,12 +6,14 @@ Django==4.2.16
 django-csp==3.8 # For Content Security Policy
 django-db-file-storage==0.5.6.1 # Support for storage in the database
 django-mysql==4.15.0
+django-redis==5.4.0
 django-tinymce==4.1.0 # Rich text editor
 django-watchman==1.3
 django-webpack-loader==3.1.1
 Pillow==11.0.0
 whitenoise==6.8.2 # For serving static files
 
+
 # DRF
 djangorestframework==3.15.2
 django-filter==24.3 # Filtering support