Django-ORM连接在每次查询之前刷新

Question

我的python模块之一(虽然与Django应用程序没有直接关联)应该使用Django模型(属于原始Django应用程序)通过Django-ORM进行方便的DB查询。但是，只有在出现DB或站点到站点连接问题之前，这才能正常工作。

按以下步骤复制100%：

1. 通过在任何python模块

中设置Django创建模型.

• 导入模型

 os.environ['DJANGO_SETTINGS_MODULE'] = 'ServiceName.settings'
 django.setup()
 from ServiceName.models import ModelName

1. 通过django使用模型在服务启动时从DB中获取一些数据(让我们称之为步骤1)，稍后通过一些触发器(让我们称之为步骤2)。在我的例子中，数据是在启动时获取一次，然后在某些Kafka事件上获取所有后续的时间。例如

query_results = ModelName.objects.filter(your_filter=some_value)

4.在第一步之后关闭PostgreSQL实例，但在第二步之前不确定是否与该问题有关，但我们使用pg-保镖作为连接点。

5.启动PostgreSQL，触发step2。

首先，获取数据的attemp在以下跟踪中失败：

Traceback (most recent call last):
File "/opt/services/_init_.py", line 113, in observe_events
if callback(event):
File "services_logparser_core.py", line 193, in process_event
r_handler.update_rules()
File "services_logparser_core.py", line 48, in update_rules
self.rules_list = self._fetch_enabled_rules()
File "services_logparser_core.py", line 69, in _fetch_enabled_rules
for sr in enabled_search_rules:
File "/usr/local/lib/python3.8/dist-packages/django/db/models/query.py", line 280, in _iter_
self._fetch_all()
File "/usr/local/lib/python3.8/dist-packages/django/db/models/query.py", line 1324, in _fetch_all
self._result_cache = list(self._iterable_class(self))
File "/usr/local/lib/python3.8/dist-packages/django/db/models/query.py", line 51, in _iter_
results = compiler.execute_sql(chunked_fetch=self.chunked_fetch, chunk_size=self.chunk_size)
File "/usr/local/lib/python3.8/dist-packages/django/db/models/sql/compiler.py", line 1175, in execute_sql
cursor.execute(sql, params)
File "/usr/local/lib/python3.8/dist-packages/django/db/backends/utils.py", line 66, in execute
return self._execute_with_wrappers(sql, params, many=False, executor=self._execute)
File "/usr/local/lib/python3.8/dist-packages/django/db/backends/utils.py", line 75, in _execute_with_wrappers
return executor(sql, params, many, context)
File "/usr/local/lib/python3.8/dist-packages/django/db/backends/utils.py", line 84, in _execute
return self.cursor.execute(sql, params)
File "/usr/local/lib/python3.8/dist-packages/django/db/utils.py", line 90, in _exit_
raise dj_exc_value.with_traceback(traceback) from exc_value
File "/usr/local/lib/python3.8/dist-packages/django/db/backends/utils.py", line 84, in _execute
return self.cursor.execute(sql, params)
django.db.utils.OperationalError: SSL SYSCALL error: EOF detected

随后所有获取数据的尝试都失败了，原因如下：

Traceback (most recent call last):
  File "/opt/services/__init__.py", line 113, in observe_events
    if callback(event):
  File "services_logparser_core.py", line 193, in process_event
    r_handler.update_rules()
  File "services_logparser_core.py", line 48, in update_rules
    self.rules_list = self._fetch_enabled_rules()
  File "services_logparser_core.py", line 69, in _fetch_enabled_rules
    for sr in enabled_search_rules:
  File "/usr/local/lib/python3.8/dist-packages/django/db/models/query.py", line 280, in __iter__
    self._fetch_all()
  File "/usr/local/lib/python3.8/dist-packages/django/db/models/query.py", line 1324, in _fetch_all
    self._result_cache = list(self._iterable_class(self))
  File "/usr/local/lib/python3.8/dist-packages/django/db/models/query.py", line 51, in __iter__
    results = compiler.execute_sql(chunked_fetch=self.chunked_fetch, chunk_size=self.chunk_size)
  File "/usr/local/lib/python3.8/dist-packages/django/db/models/sql/compiler.py", line 1173, in execute_sql
    cursor = self.connection.cursor()
  File "/usr/local/lib/python3.8/dist-packages/django/utils/asyncio.py", line 26, in inner
    return func(*args, **kwargs)
  File "/usr/local/lib/python3.8/dist-packages/django/db/backends/base/base.py", line 259, in cursor
    return self._cursor()
  File "/usr/local/lib/python3.8/dist-packages/django/db/backends/base/base.py", line 237, in _cursor
    return self._prepare_cursor(self.create_cursor(name))
  File "/usr/local/lib/python3.8/dist-packages/django/db/utils.py", line 90, in __exit__
    raise dj_exc_value.with_traceback(traceback) from exc_value
  File "/usr/local/lib/python3.8/dist-packages/django/db/backends/base/base.py", line 237, in _cursor
    return self._prepare_cursor(self.create_cursor(name))
  File "/usr/local/lib/python3.8/dist-packages/django/utils/asyncio.py", line 26, in inner
    return func(*args, **kwargs)
  File "/usr/local/lib/python3.8/dist-packages/django/db/backends/postgresql/base.py", line 236, in create_cursor
    cursor = self.connection.cursor()
django.db.utils.InterfaceError: connection already closed

应用程序重新启动修复了问题。

我没有在任何地方手动设置到数据库的连接(我只设置了db凭据)，所有的连接都由Django ORM处理。在项目中是否可以配置任何django/psycopg设置，以便每次需要db查询时都建立新的连接？

Django==3.2.6

Answer 1

from django import db

和

db.close_old_connections()

在此之前

query_results = ModelName.objects.filter(your_filter=some_value)

成功了。close_old_connections()方法不仅关闭旧连接，还检查当前连接是否仍然可用。如果连接返回错误，它将被关闭。新连接自动打开。