[fix] Ensure VpnClient post_delete signal fires on template removal openwisp#1221

Replaced QuerySet.delete() with per-instance .delete() calls
so that post_delete signals fire correctly for each VpnClient.

Wrapped both deletion loops in transaction.atomic() to ensure
atomicity and prevent partial deletions on failure, consistent
with the pattern already used in serializers.py.

Used .iterator() for memory-safe iteration over potentially
large querysets.

Signed-off-by: prakash-kalwaniya <kalwaniyaprakash1@gmail.com>

Author: mn-ram

openwisp_controller/config/api/serializers.py

@@ -202,7 +202,10 @@ def _update_config(self, device, config_data):
                 with transaction.atomic():
                     vpn_list = config.templates.filter(type="vpn").values_list("vpn")
                     if vpn_list:
-                        config.vpnclient_set.exclude(vpn__in=vpn_list).delete()
+                        for vpnclient in config.vpnclient_set.exclude(
+                            vpn__in=vpn_list
+                        ).iterator():
+                            vpnclient.delete()
                     config.templates.set(config_templates, clear=True)
             config.save()
         except ValidationError as error:

openwisp_controller/config/base/config.py

@@ -338,7 +338,9 @@ def manage_vpn_clients(cls, action, instance, pk_set, **kwargs):
             if instance.is_deactivating_or_deactivated():
                 # If the device is deactivated or in the process of deactivating, then
                 # delete all vpn clients and return.
-                instance.vpnclient_set.all().delete()
+                with transaction.atomic():
+                    for vpnclient in instance.vpnclient_set.all().iterator():
+                        vpnclient.delete()
             return
 
         vpn_client_model = cls.vpn.through
@@ -370,9 +372,11 @@ def manage_vpn_clients(cls, action, instance, pk_set, **kwargs):
             # signal is triggered again—after all templates, including the required
             # ones, have been fully added. At that point, we can identify and
             # delete VpnClient objects not linked to the final template set.
-            instance.vpnclient_set.exclude(
-                template_id__in=instance.templates.values_list("id", flat=True)
-            ).delete()
+            with transaction.atomic():
+                for vpnclient in instance.vpnclient_set.exclude(
+                    template_id__in=instance.templates.values_list("id", flat=True)
+                ).iterator():
+                    vpnclient.delete()
 
         if action == "post_add":
             for template in templates.filter(type="vpn"):