Simplify the race condition fix using F()

apiserver/apiserver/api/views.py

@@ -4,7 +4,7 @@ logger = logging.getLogger(__name__)
 from django.contrib.auth.models import User, Group
 from django.shortcuts import get_object_or_404, redirect
 from django.db import transaction
-from django.db.models import Max
+from django.db.models import Max, F
 from django.db.utils import OperationalError
 from django.http import HttpResponse, Http404, FileResponse
 from django.core.files.base import File
@@ -505,8 +505,6 @@ class StatsViewSet(viewsets.ViewSet, List):
 
     @action(detail=False, methods=['post'])
     def track(self, request):
-        try:
-            with transaction.atomic():
         if 'name' not in request.data:
             raise exceptions.ValidationError(dict(name='This field is required.'))
 
@@ -539,15 +537,11 @@ class StatsViewSet(viewsets.ViewSet, List):
             )
             logging.info('New ' + devicename + ' session created for: ' + username)
         else:
-                    last_session.num_seconds += 10
-                    last_session.save()
+            last_session.num_seconds = F('num_seconds') + 10
+            last_session.save(update_fields=['num_seconds'])
 
         return Response(200)
 
-        # keep trying if we hit a "database locked" error
-        except OperationalError:
-            return self.track(request)
-
 
 class MemberCountViewSet(Base, List):
     pagination_class = None