perf: 优化 Session 支持 duration 字段

apps/terminal/models/session/session.py

@@ -2,6 +2,7 @@ from __future__ import unicode_literals
 
 import os
 import uuid
+from datetime import timedelta
 
 from django.conf import settings
 from django.core.cache import cache
@@ -233,6 +234,14 @@ class Session(OrgModelMixin):
         target_ip = instance.get_target_ip() if instance else ''
         return target_ip
 
+    @property
+    def duration(self):
+        date_end = self.date_end or timezone.now()
+        delta = date_end - self.date_start
+        # 去掉毫秒的显示
+        delta = timedelta(seconds=int(delta.total_seconds()))
+        return str(delta)
+
     @classmethod
     def generate_fake(cls, count=100, is_finished=True):
         import random