diff --git a/apps/assets/models/asset.py b/apps/assets/models/asset.py
index a5e57876051bc0d6de88c724cfd581df8d6d850b..4aaa0287dbbca0cf7d4de5fb6d1328b5ef4217b3 100644
--- a/apps/assets/models/asset.py
+++ b/apps/assets/models/asset.py
@@ -49,7 +49,7 @@ class Asset(models.Model):
     ip = models.GenericIPAddressField(max_length=32, verbose_name=_('IP'), db_index=True)
     hostname = models.CharField(max_length=128, unique=True, verbose_name=_('Hostname'))
     port = models.IntegerField(default=22, verbose_name=_('Port'))
-    domain = models.ForeignKey("assets.Domain", null=True, blank=True, related_name='assets', verbose_name=_("Domain"))
+    domain = models.ForeignKey("assets.Domain", null=True, blank=True, related_name='assets', verbose_name=_("Domain"), on_delete=models.SET_NULL)
     nodes = models.ManyToManyField('assets.Node', default=default_node, related_name='assets', verbose_name=_("Nodes"))
     is_active = models.BooleanField(default=True, verbose_name=_('Is active'))
 
diff --git a/apps/ops/celery/signal_handler.py b/apps/ops/celery/signal_handler.py
index 8309c0246489d8b09072daefc6cf21e9a6f26386..c64befbb7faaba56c9fd6988129e07030053e45c 100644
--- a/apps/ops/celery/signal_handler.py
+++ b/apps/ops/celery/signal_handler.py
@@ -3,6 +3,7 @@
 import os
 import datetime
 import sys
+import time
 
 from django.conf import settings
 from django.utils import timezone
@@ -53,10 +54,19 @@ def after_task_publish_signal_handler(sender, headers=None, **kwargs):
     CeleryTask.objects.create(
         id=headers["id"], status=CeleryTask.WAITING, name=headers["task"]
     )
+    cache.set(headers["id"], True, 3600)
 
 
 @task_prerun.connect
 def pre_run_task_signal_handler(sender, task_id=None, task=None, **kwargs):
+    time.sleep(0.1)
+    for i in range(5):
+        if cache.get(task_id, False):
+            break
+        else:
+            time.sleep(0.1)
+            continue
+
     t = get_object_or_none(CeleryTask, id=task_id)
     if t is None:
         logger.warn("Not get the task: {}".format(task_id))
diff --git a/apps/users/api.py b/apps/users/api.py
index df2f2079cdd8414286b9bcb1ed01cd8042ac9106..69818f741b7af7d8e842b8835599689b73133dc0 100644
--- a/apps/users/api.py
+++ b/apps/users/api.py
@@ -28,7 +28,7 @@ class UserViewSet(IDInFilterMixin, BulkModelViewSet):
     queryset = User.objects.exclude(role="App")
     # queryset = User.objects.all().exclude(role="App").order_by("date_joined")
     serializer_class = UserSerializer
-    permission_classes = (IsSuperUser, IsAuthenticated)
+    permission_classes = (IsSuperUserOrAppUser, IsAuthenticated)
     filter_fields = ('username', 'email', 'name', 'id')