fix: stop rewriting the user row on every login (the actual cause of connection exhaustion)

api/utils/keycloak_utils.py

@@ -86,7 +86,11 @@ def validate_token(
                     from authorization.models import User
 
                     user = User.objects.get(id=user_id)
-                    user.save()
+                    # Deliberately no user.save() here. It rewrote every
+                    # column of an unchanged row on every authenticated
+                    # request, taking a row lock for no benefit - and since
+                    # concurrent requests for one user contend on that single
+                    # row, it serialized them against each other.
 
                     # NOTE: Organizations are managed in DataSpace database, not Keycloak
                     # Organization memberships should be created/managed through DataSpace's
@@ -412,13 +416,35 @@ def sync_user_from_keycloak(
                     )
 
             if user:
-                # Update existing user
-                user.keycloak_id = keycloak_id
-                user.username = username
-                user.email = email
-                user.first_name = user_info.get("given_name", "") or user.first_name
-                user.last_name = user_info.get("family_name", "") or user.last_name
-                user.is_active = True
+                # Update existing user, but only write when something actually
+                # changed. The unconditional save this replaces was the cause
+                # of the connection exhaustion: every login rewrote the same
+                # row, so concurrent logins for one user queued on a row lock
+                # (pg_stat_activity showed "Lock: tuple" and
+                # "Lock: transactionid" on UPDATE "ds_user"), each holding a
+                # database connection while it waited.
+                desired = {
+                    "keycloak_id": keycloak_id,
+                    "username": username,
+                    "email": email,
+                    "first_name": user_info.get("given_name", "") or user.first_name,
+                    "last_name": user_info.get("family_name", "") or user.last_name,
+                    "is_active": True,
+                    "is_staff": "admin" in roles,
+                    "is_superuser": "admin" in roles,
+                }
+                changed = [
+                    field
+                    for field, value in desired.items()
+                    if getattr(user, field) != value
+                ]
+                if changed:
+                    for field in changed:
+                        setattr(user, field, desired[field])
+                    # update_fields keeps the UPDATE narrow instead of
+                    # rewriting every column.
+                    user.save(update_fields=changed)
+                return user
             else:
                 # Create new user
                 user = User(