From 166387b6908f2e107d09c5649a204d0eba875456 Mon Sep 17 00:00:00 2001
From: Lennard Strohmeyer <lennard.strohmeyer@digitallearning.gmbh>
Date: Tue, 17 Dec 2024 10:51:34 +0100
Subject: [PATCH] #87: added mutex to hopefully prevent rare race condition
when creating a new user from a shibboleth account
---
src/backend/.env.dist | 5 ++++-
src/backend/.env.test | 5 ++++-
src/backend/settings.py | 9 +++++++++
src/consents/views.py | 38 ++++++++++++++++++++++++++++++--------
src/xapi/views.py | 2 +-
5 files changed, 48 insertions(+), 11 deletions(-)
diff --git a/src/backend/.env.dist b/src/backend/.env.dist
index cf392f8..add1bca 100644
--- a/src/backend/.env.dist
+++ b/src/backend/.env.dist
@@ -18,4 +18,7 @@ IDP_ENABLED=
SP_HOST=
ANONYMIZATION_HASH_PREFIX=anon
-ANONYMIZATION_DEFAULT_MINIMUM_COUNT=10
\ No newline at end of file
+ANONYMIZATION_DEFAULT_MINIMUM_COUNT=10
+
+CACHE_BACKEND='redis'
+CACHE_URI='redis://127.0.0.1:6379'
\ No newline at end of file
diff --git a/src/backend/.env.test b/src/backend/.env.test
index 74be673..803a7a2 100644
--- a/src/backend/.env.test
+++ b/src/backend/.env.test
@@ -17,4 +17,7 @@ IDP_SERVER=https://aai-test-v3.ruhr-uni-bochum.de
SP_HOST=
ANONYMIZATION_HASH_PREFIX=anon
-ANONYMIZATION_DEFAULT_MINIMUM_COUNT=10
\ No newline at end of file
+ANONYMIZATION_DEFAULT_MINIMUM_COUNT=10
+
+CACHE_BACKEND='redis'
+CACHE_URI='redis://127.0.0.1:6379'
\ No newline at end of file
diff --git a/src/backend/settings.py b/src/backend/settings.py
index 258d1fc..e3bd093 100644
--- a/src/backend/settings.py
+++ b/src/backend/settings.py
@@ -127,6 +127,15 @@ else:
}
}
+# Cache(s)
+# https://docs.djangoproject.com/en/4.1/topics/cache/
+CACHES = {
+ 'default': {
+ 'BACKEND': 'django.core.cache.backends.redis.RedisCache' if env("CACHE_BACKEND", default="file") == "redis"
+ else 'django.core.cache.backends.filebased.FileBasedCache',
+ 'LOCATION': '/tmp/django_cache' if env("CACHE_BACKEND", default="file") == 'file' else env("CACHE_URI", default='redis://127.0.0.1:6379') ,
+ }
+}
# Password validation
# https://docs.djangoproject.com/en/4.1/ref/settings/#auth-password-validators
diff --git a/src/consents/views.py b/src/consents/views.py
index 22ebda2..680047a 100644
--- a/src/consents/views.py
+++ b/src/consents/views.py
@@ -3,7 +3,9 @@ import string
import random
import os
import secrets
+import time
+from django.core.cache import cache
from django.conf import settings
from django.core.exceptions import ObjectDoesNotExist
from django.http.response import JsonResponse
@@ -391,18 +393,38 @@ class CreateUserConsentViaConnectServiceView(APIView):
shib_id = shib_connector_resolver_to_pairwaise_id(email=email, provider=provider)
user = CustomUser.objects.filter(shibboleth_connector_identifier=shib_id).first()
-
+
+ message = "user exists"
if not user:
- user = CustomUser.objects.create(
- shibboleth_connector_identifier=shib_id, # this is the pairwaise id
- email=''.join(random.choices(string.ascii_uppercase + string.digits, k=8)) + "@manual-created.polaris",
- first_name=''.join(random.choices(string.ascii_uppercase + string.digits, k=8)),
- last_name=''.join(random.choices(string.ascii_uppercase + string.digits, k=8))
- )
+ lock_key = f"user_creation_lock_{shib_id}" # "mutex" to prevent race conditions using a cache entry
+ if cache.add(lock_key, "locked", 2): # 2 is a timeout value, after wich the cache entry is deleted
+ try:
+ user = CustomUser.objects.create(
+ shibboleth_connector_identifier=shib_id, # this is the pairwise id
+ email=''.join(random.choices(string.ascii_uppercase + string.digits, k=8)) + "@manual-created.polaris",
+ first_name=''.join(random.choices(string.ascii_uppercase + string.digits, k=8)),
+ last_name=''.join(random.choices(string.ascii_uppercase + string.digits, k=8))
+ )
+ except Exception as e:
+ return JsonResponse({"message": "user could not be created"}, safe=False,
+ status=status.HTTP_500_INTERNAL_SERVER_ERROR)
+ finally:
+ message = "user has been created"
+ cache.delete(lock_key)
+ else:
+ for _ in range(4): # Wait up to 2x lock_timeout
+ time.sleep(0.1)
+ if not cache.get(lock_key):
+ break
+ # Fetch the user created by another process
+ user = CustomUser.objects.filter(shibboleth_connector_identifier=shib_id).first()
+ if not user:
+ return JsonResponse({"message": "user could not be created"}, safe=False,
+ status=status.HTTP_500_INTERNAL_SERVER_ERROR)
return JsonResponse(
{
- "message": "user is created",
+ "message": message,
},
safe=False,
status=status.HTTP_200_OK,
diff --git a/src/xapi/views.py b/src/xapi/views.py
index ed18d1d..00262b4 100644
--- a/src/xapi/views.py
+++ b/src/xapi/views.py
@@ -85,7 +85,7 @@ def shib_connector_resolver_to_pairwaise_id(email, provider):
additionalData = None
shib_id = client.service.GetOrGenerateIdAndConnect(app_secret, user_id, lrs_type, linkType, processId, additionalData)
if len(shib_id) != 1:
- print("Multiple pairwaise ids found, only use the first one!")
+ print("Multiple pairwise ids found, only use the first one!")
shib_id = shib_id[0]
if settings.DEBUG:
print("Result shib_id: {0}".format(shib_id))
--
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