Fixes #3489: Prevent exception triggered by webhook upon object deletion

CHANGELOG.md

@@ -7,6 +7,10 @@ v2.6.4 (FUTURE)
 * [#3318](https://github.com/netbox-community/netbox/issues/3318) - Increase length of platform name and slug to 64 characters
 * [#3341](https://github.com/netbox-community/netbox/issues/3341) - Add Inline Vlan Editing
 
+## Bug Fixes
+
+* [#3489](https://github.com/netbox-community/netbox/issues/3489) - Prevent exception triggered by webhook upon object deletion
+
 v2.6.3 (2019-09-04)
 
 ## New Features

netbox/extras/middleware.py

@@ -6,6 +6,7 @@ from datetime import timedelta
 from django.conf import settings
 from django.db.models.signals import post_delete, post_save
 from django.utils import timezone
+from django.utils.functional import curry
 from django_prometheus.models import model_deletes, model_inserts, model_updates
 
 from .constants import (
@@ -18,10 +19,11 @@ from .webhooks import enqueue_webhooks
 _thread_locals = threading.local()
 
 
-def cache_changed_object(sender, instance, **kwargs):
+def handle_changed_object(sender, instance, **kwargs):
     """
-    Cache an object being created or updated for the changelog.
+    Fires when an object is created or updated
     """
+    # Queue the object and a new ObjectChange for processing once the request completes
     if hasattr(instance, 'to_objectchange'):
         action = OBJECTCHANGE_ACTION_CREATE if kwargs['created'] else OBJECTCHANGE_ACTION_UPDATE
         objectchange = instance.to_objectchange(action)
@@ -30,15 +32,22 @@ def cache_changed_object(sender, instance, **kwargs):
         )
 
 
-def cache_deleted_object(sender, instance, **kwargs):
+def _handle_deleted_object(request, sender, instance, **kwargs):
     """
-    Cache an object being deleted for the changelog.
+    Fires when an object is deleted
     """
+    # Record an Object Change
     if hasattr(instance, 'to_objectchange'):
         objectchange = instance.to_objectchange(OBJECTCHANGE_ACTION_DELETE)
-        _thread_locals.changed_objects.append(
-            (instance, objectchange)
-        )
+        objectchange.user = request.user
+        objectchange.request_id = request.id
+        objectchange.save()
+
+    # Enqueue webhooks
+    enqueue_webhooks(instance, request.user, request.id, OBJECTCHANGE_ACTION_DELETE)
+
+    # Increment metric counters
+    model_deletes.labels(instance._meta.model_name).inc()
 
 
 def purge_objectchange_cache(sender, **kwargs):
@@ -54,7 +63,7 @@ class ObjectChangeMiddleware(object):
 
         1. Create an ObjectChange to reflect the modification to the object in the changelog.
         2. Enqueue any relevant webhooks.
-        3. Increment metric counter for the event type
+        3. Increment the metric counter for the event type.
 
     The post_save and post_delete signals are employed to catch object modifications, however changes are recorded a bit
     differently for each. Objects being saved are cached into thread-local storage for action *after* the response has
@@ -74,9 +83,12 @@ class ObjectChangeMiddleware(object):
         # the same request.
         request.id = uuid.uuid4()
 
+        # Signals don't include the request context, so we're currying it into the post_delete function ahead of time.
+        handle_deleted_object = curry(_handle_deleted_object, request)
+
         # Connect our receivers to the post_save and post_delete signals.
-        post_save.connect(cache_changed_object, dispatch_uid='cache_changed_object')
-        post_delete.connect(cache_deleted_object, dispatch_uid='cache_deleted_object')
+        post_save.connect(handle_changed_object, dispatch_uid='cache_changed_object')
+        post_delete.connect(handle_deleted_object, dispatch_uid='cache_deleted_object')
 
         # Provide a hook for purging the change cache
         purge_changelog.connect(purge_objectchange_cache)
@@ -104,8 +116,6 @@ class ObjectChangeMiddleware(object):
                 model_inserts.labels(obj._meta.model_name).inc()
             elif objectchange.action == OBJECTCHANGE_ACTION_UPDATE:
                 model_updates.labels(obj._meta.model_name).inc()
-            elif objectchange.action == OBJECTCHANGE_ACTION_DELETE:
-                model_deletes.labels(obj._meta.model_name).inc()
 
         # Housekeeping: 1% chance of clearing out expired ObjectChanges. This applies only to requests which result in
         # one or more changes being logged.