perf: 优化 celery 任务中的数据库连接问题

perf: add comment

apps/ops/signals_handler.py

@@ -1,6 +1,8 @@
 from django.utils import translation
 from django.core.cache import cache
-from celery.signals import task_prerun, before_task_publish
+from celery.signals import task_prerun, task_postrun, before_task_publish
+
+from common.db.utils import close_old_connections
 
 
 TASK_LANG_CACHE_KEY = 'TASK_LANG_{}'
@@ -17,7 +19,16 @@ def before_task_publish(headers=None, **kwargs):
 
 @task_prerun.connect()
 def on_celery_task_pre_run(task_id='', **kwargs):
+    # 关闭之前的数据库连接
+    close_old_connections()
+
+    # 保存 Lang context
     key = TASK_LANG_CACHE_KEY.format(task_id)
     task_lang = cache.get(key)
     if task_lang:
         translation.activate(task_lang)
+
+
+@task_postrun.connect()
+def on_celery_task_post_run(**kwargs):
+    close_old_connections()