Django-ORM 数据库连接在每次查询前刷新

Question

我的 python 模块之一（与 Django 应用程序不直接关联，尽管是同一项目）应该使用 Django 模型（属于原始 Django 应用程序）通过 Django-ORM 进行方便的数据库查询。 但是，只有在出现数据库或站点到站点连接问题时，此方法才有效。

通过以下步骤复制 100% 次：

1. 创建模型。
2. 通过在任何 python 模块中设置 Django 来导入模型

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

3. 通过 django ORM 使用模型在服务启动时从数据库中获取一些数据（我们称之为步骤 1），稍后通过一些触发器（我们称之为步骤 2）。在我的例子中，数据在启动时获取一次，并在特定的 Kafka 事件上获取所有后续时间。 例如

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

4. 在步骤 1 之后、步骤 2 之前关闭 PostgreSQL 实例 不确定是否与该问题相关，但我们使用 pg-bouncer 作为连接点。

5.启动PostgreSQL，触发step2。

第一次尝试获取数据失败，并显示以下跟踪：

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

所有后续尝试获取数据均失败，并显示：

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。

我不会在任何地方手动设置与数据库的连接（我只设置数据库凭据），所有连接均由 Django ORM 处理。 是否可以在项目内配置任何 django/psycopg 设置，以便每次需要数据库查询时建立新连接？

姜戈==3.2.6

Answer 1

from django import db

以前

db.close_old_connections()

做到了

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

这一点。
COLLES_OLD_CONNECTIONS（）方法不仅关闭旧连接，还可以检查当前连接是否仍然可用。如果连接返回错误，则将关闭它。新连接会自动打开。