Adapted change logging to queue changes in thread-local storage and record them at the end of the request

netbox/extras/middleware.py

@@ -2,20 +2,25 @@ from __future__ import unicode_literals
 
 from datetime import timedelta
 import random
+import threading
 import uuid
 
 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, SimpleLazyObject
 
 from .constants import OBJECTCHANGE_ACTION_CREATE, OBJECTCHANGE_ACTION_DELETE, OBJECTCHANGE_ACTION_UPDATE
 from .models import ObjectChange
 
 
-def record_object_change(user, request_id, instance, **kwargs):
+_thread_locals = threading.local()
+
+
+def mark_object_changed(instance, **kwargs):
     """
-    Create an ObjectChange in response to an object being created or deleted.
+    Mark an object as having been created, saved, or updated. At the end of the request, this change will be recorded.
+    We have to wait until the *end* of the request to the serialize the object, because related fields like tags and
+    custom fields have not yet been updated when the post_save signal is emitted.
     """
     if not hasattr(instance, 'log_change'):
         return
@@ -27,14 +32,7 @@ def record_object_change(user, request_id, instance, **kwargs):
     else:
         action = OBJECTCHANGE_ACTION_DELETE
 
-    instance.log_change(user, request_id, action)
-
-    # 1% chance of clearing out expired ObjectChanges
-    if settings.CHANGELOG_RETENTION and random.randint(1, 100) == 1:
-        cutoff = timezone.now() - timedelta(days=settings.CHANGELOG_RETENTION)
-        purged_count, _ = ObjectChange.objects.filter(
-            time__lt=cutoff
-        ).delete()
+    _thread_locals.changed_objects.append((instance, action))
 
 
 class ChangeLoggingMiddleware(object):
@@ -44,22 +42,30 @@ class ChangeLoggingMiddleware(object):
 
     def __call__(self, request):
 
-        def get_user(request):
-            return request.user
+        # Initialize the list of changed objects
+        _thread_locals.changed_objects = []
+
+        # Assign a random unique ID to the request. This will be used to associate multiple object changes made during
+        # the same request.
+        request.id = uuid.uuid4()
 
-        # DRF employs a separate authentication mechanism outside Django's normal request/response cycle, so calling
-        # request.user in middleware will always return AnonymousUser for API requests. To work around this, we point
-        # to a lazy object that doesn't resolve the user until after DRF's authentication has been called. For more
-        # detail, see https://stackoverflow.com/questions/26240832/
-        user = SimpleLazyObject(lambda: get_user(request))
+        # Connect mark_object_changed to the post_save and post_delete receivers
+        post_save.connect(mark_object_changed, dispatch_uid='record_object_saved')
+        post_delete.connect(mark_object_changed, dispatch_uid='record_object_deleted')
 
-        request_id = uuid.uuid4()
+        # Process the request
+        response = self.get_response(request)
 
-        # Django doesn't provide any request context with the post_save/post_delete signals, so we curry
-        # record_object_change() to include the user associated with the current request.
-        _record_object_change = curry(record_object_change, user, request_id)
+        # Record object changes
+        for obj, action in _thread_locals.changed_objects:
+            if obj.pk:
+                obj.log_change(request.user, request.id, action)
 
-        post_save.connect(_record_object_change, dispatch_uid='record_object_saved')
-        post_delete.connect(_record_object_change, dispatch_uid='record_object_deleted')
+        # Housekeeping: 1% chance of clearing out expired ObjectChanges
+        if _thread_locals.changed_objects and settings.CHANGELOG_RETENTION and random.randint(1, 100) == 1:
+            cutoff = timezone.now() - timedelta(days=settings.CHANGELOG_RETENTION)
+            purged_count, _ = ObjectChange.objects.filter(
+                time__lt=cutoff
+            ).delete()
 
-        return self.get_response(request)
+        return response