Fix race condition in version slug generation (#133)

The previous use of `select_for_update` fell out of scope too quickly and caused the lock on the database to be removed too quickly. This potentially allowed a race condition if, for example, a user hit the "Create new version" button too many times and the queries were evaluated at the same time. It is possible that this caused the duplicate slug issue that we've observed before, in some cases.
ChameleonCloud · Aug 2, 2023 · 7ab2554 · 7ab2554
1 parent 6fecb08
commit 7ab2554
Showing 1 changed file with 6 additions and 8 deletions.
diff --git a/trovi/models.py b/trovi/models.py
@@ -299,14 +299,12 @@ def generate_slug(instance: "ArtifactVersion", created: bool = False, **_):
             time_stamp = instance.created_at.strftime("%Y-%m-%d")
             with transaction.atomic():
                 if instance.artifact:
-                    versions_today = (
-                        instance.artifact.versions.filter(
-                            artifact__created_at__date=instance.created_at.date(),
-                        )
-                        .exclude(slug__exact="")
-                        .select_for_update()
-                        .count()
-                    )
+                    versions_today_query = instance.artifact.versions.filter(
+                        artifact__created_at__date=instance.created_at.date(),
+                    ).select_for_update()
+                    versions_today = versions_today_query.exclude(
+                        slug__exact=""
+                    ).count()
                 else:
                     versions_today = 0
                 if versions_today: