[bug] Changing DeviceGroup.context invalidates config checksum cache #798

Closes #798

Author: pandafy

openwisp_controller/config/base/device_group.py

@@ -15,6 +15,7 @@
 from .. import settings as app_settings
 from ..signals import group_templates_changed
 from ..sortedm2m.fields import SortedManyToManyField
+from ..tasks import bulk_invalidate_config_get_cached_checksum
 from .config import TemplatesThrough
 
 
@@ -75,6 +76,19 @@ def clean(self):
         except SchemaError as e:
             raise ValidationError({'input': e.message})
 
+    def save(
+        self, force_insert=False, force_update=False, using=None, update_fields=None
+    ):
+        context_changed = False
+        if not self._state.adding:
+            db_instance = self.__class__.objects.only('context').get(id=self.id)
+            context_changed = db_instance.context != self.context
+        super().save(force_insert, force_update, using, update_fields)
+        if context_changed:
+            bulk_invalidate_config_get_cached_checksum.delay(
+                {'device__group_id': str(self.id)}
+            )
+
     def get_context(self):
         return deepcopy(self.context)
 

openwisp_controller/config/tests/test_device.py

@@ -394,6 +394,31 @@ def test_changing_org_variable_invalidates_cache(self):
         new_checksum = config.get_cached_checksum()
         self.assertNotEqual(old_checksum, new_checksum)
 
+    def test_changing_group_variable_invalidates_cache(self):
+        org = self._get_org()
+        device_group = self._create_device_group(organization=org, context={})
+        device = self._create_device(organization=org, group=device_group)
+        config = self._create_config(device=device)
+        template = self._create_template(
+            config={'interfaces': [{'name': 'eth0', 'type': '{{ interface_type }}'}]},
+            default_values={'interface_type': 'ethernet'},
+        )
+        config.templates.add(template)
+        old_checksum = config.get_cached_checksum()
+
+        # Changing DeviceGroup.context should invalidate the cache
+        # and a new checksum should be returned in the following request.
+        device_group.context = {'interface_type': 'virtual'}
+        device_group.full_clean()
+        device_group.save()
+
+        # Config.backend_instance is a "cached_property", hence deleting
+        # the attribute is required for testing.
+        del config.backend_instance
+
+        new_checksum = config.get_cached_checksum()
+        self.assertNotEqual(old_checksum, new_checksum)
+
     def test_management_ip_changed_not_emitted_on_creation(self):
         with catch_signal(management_ip_changed) as handler:
             self._create_device(organization=self._get_org())