事务管理错误 - 当'原子'块处于活动状态时这是被禁止的

Question

在把我的项目从django 1.5.1升级到1.6.5的时候，我遇到了一个奇怪的问题。

当一个“原子”块处于活动状态时，这是不允许的。

我知道django 1.6对数据库事务的变化，并且已经根据这些变化调整了设置。大部分情况下都能正常工作，但在访问request.user对象时就出问题了。

比如说，这段代码：

with transaction.atomic():
    if hasattr(request, 'user') and getattr(request.user, 'id', None):
        #blah

这是错误追踪信息：

Environment:


Request Method: GET
Request URL: <domain>/api/v1/browser_id/

Django Version: 1.6.5
Python Version: 2.7.3

<Installed Applications & Middlewares snipped for brevity>

Traceback:
File "/usr/local/virtualenvs/karthik-django165/local/lib/python2.7/site-packages/django/core/handlers/base.py" in get_response
  112.                     response = wrapped_callback(request, *callback_args, **callback_kwargs)
File "/usr/local/virtualenvs/karthik-django165/local/lib/python2.7/site-packages/django/db/transaction.py" in inner
  371.                 return func(*args, **kwargs)
File "/home/kravindra/workspace/puppysite/puppy/kennel/views/etag_session.py" in browser_id
  43.         if hasattr(request, 'user') and getattr(request.user, 'id', None):
File "/usr/local/virtualenvs/karthik-django165/local/lib/python2.7/site-packages/django/utils/functional.py" in inner
  213.             self._setup()
File "/usr/local/virtualenvs/karthik-django165/local/lib/python2.7/site-packages/django/utils/functional.py" in _setup
  298.         self._wrapped = self._setupfunc()
File "/usr/local/virtualenvs/karthik-django165/local/lib/python2.7/site-packages/django/contrib/auth/middleware.py" in <lambda>
  18.         request.user = SimpleLazyObject(lambda: get_user(request))
File "/usr/local/virtualenvs/karthik-django165/local/lib/python2.7/site-packages/django/contrib/auth/middleware.py" in get_user
  10.         request._cached_user = auth.get_user(request)
File "/usr/local/virtualenvs/karthik-django165/local/lib/python2.7/site-packages/django/contrib/auth/__init__.py" in get_user
  140.         user_id = request.session[SESSION_KEY]
File "/usr/local/virtualenvs/karthik-django165/local/lib/python2.7/site-packages/django/contrib/sessions/backends/base.py" in __getitem__
  47.         return self._session[key]
File "/usr/local/virtualenvs/karthik-django165/local/lib/python2.7/site-packages/django/contrib/sessions/backends/base.py" in _get_session
  173.                 self._session_cache = self.load()
File "/usr/local/virtualenvs/karthik-django165/local/lib/python2.7/site-packages/django/contrib/sessions/backends/cached_db.py" in load
  52.                 self.create()
File "/usr/local/virtualenvs/karthik-django165/local/lib/python2.7/site-packages/django/contrib/sessions/backends/db.py" in create
  40.                 self.save(must_create=True)
File "/usr/local/virtualenvs/karthik-django165/local/lib/python2.7/site-packages/django/contrib/sessions/backends/cached_db.py" in save
  62.         super(SessionStore, self).save(must_create)
File "/usr/local/virtualenvs/karthik-django165/local/lib/python2.7/site-packages/django/contrib/sessions/backends/db.py" in save
  63.                 obj.save(force_insert=must_create, using=using)
File "/usr/local/virtualenvs/karthik-django165/local/lib/python2.7/site-packages/django/db/models/base.py" in save
  545.                        force_update=force_update, update_fields=update_fields)
File "/usr/local/virtualenvs/karthik-django165/local/lib/python2.7/site-packages/django/db/models/base.py" in save_base
  582.                                    update_fields=update_fields, raw=raw, using=using)
File "/usr/local/virtualenvs/karthik-django165/local/lib/python2.7/site-packages/django/dispatch/dispatcher.py" in send
  185.             response = receiver(signal=self, sender=sender, **named)
File "/usr/local/virtualenvs/karthik-django165/local/lib/python2.7/site-packages/django/db/transaction.py" in inner
  430.             with self:
File "/usr/local/virtualenvs/karthik-django165/local/lib/python2.7/site-packages/django/db/transaction.py" in __enter__
  422.         self.entering(self.using)
File "/usr/local/virtualenvs/karthik-django165/local/lib/python2.7/site-packages/django/db/transaction.py" in entering
  483.         enter_transaction_management(using=using)
File "/usr/local/virtualenvs/karthik-django165/local/lib/python2.7/site-packages/django/db/transaction.py" in enter_transaction_management
  70.     get_connection(using).enter_transaction_management(managed, forced)
File "/usr/local/virtualenvs/karthik-django165/local/lib/python2.7/site-packages/django/db/backends/__init__.py" in enter_transaction_management
  287.         self.validate_no_atomic_block()
File "/usr/local/virtualenvs/karthik-django165/local/lib/python2.7/site-packages/django/db/backends/__init__.py" in validate_no_atomic_block
  367.                 "This is forbidden when an 'atomic' block is active.")

Exception Type: TransactionManagementError at /api/v1/browser_id/
Exception Value: This is forbidden when an 'atomic' block is active.

从错误追踪信息来看，

/usr/local/virtualenvs/karthik-django165/local/lib/python2.7/site-packages/django/contrib/sessions/backends/cached_db.py in load
                self.create() ...
▼ Local vars
Variable    Value
e   
DoesNotExist('Session matching query does not exist.',)
self    
<django.contrib.sessions.backends.cached_db.SessionStore object at 0x7f61d401c6d0>
data    
None

SessionStore引发了一个异常。

我使用的是POSTGRES作为后端数据库。与后端会话存储相关的设置是：

SESSION_ENGINE = 'django.contrib.sessions.backends.cached_db' #which is persistent storage

ATOMIC_REQUESTS = True

有没有什么建议可以解决这个问题？

我发现有很多关于TransactionManagementError的问题在SO和博客上讨论，但没有特别针对这个问题的解决方案。

Answer 1

从错误信息来看，你的某个 post_save 信号接收器还在使用一些已经不推荐使用的 transaction 接口：

• transaction.Transaction
• transaction.autocommit
• transaction.commit_on_success
• transaction.commit_manually
• commit_on_success_unless_managed

确保把这些替换成 transaction.atomic，这样你的问题就应该解决了。

如果你找不到问题的接收器，随时告诉我。