This is not a feature request per se, but it is not exactly a bug report
either.
We are recently upgrading from Django 1.5 to Django 1.6.7. One other
relevant package version of interest is psycopg2 which is at 2.5.4.
After upgrade, many test cases were failing with the classic
"InterfaceError: connection already closed" originating from psycopg2. Here
is a typical stack trace in which user-name and app-name have been obscured.
File "/home/user1/sme-appname/src/session_csrf/__init__.py", line 68, in
process_view
token = cache.get(PREFIX + key, '')
File
"/home/user1/sme-appname/lib/python2.7/site-packages/django/core/cache/backends/db.py",
line 61, in get
cursor = connections[db].cursor()
File
"/home/user1/sme-appname/lib/python2.7/site-packages/django/db/backends/__init__.py",
line 162, in cursor
cursor = util.CursorWrapper(self._cursor(), self)
File
"/home/user1/sme-appname/lib/python2.7/site-packages/django/db/backends/__init__.py",
line 134, in _cursor
return self.create_cursor()
File
"/home/user1/sme-appname/lib/python2.7/site-packages/django/db/utils.py",
line 99, in __exit__
six.reraise(dj_exc_type, dj_exc_value, traceback)
File
"/home/user1/sme-appname/lib/python2.7/site-packages/django/db/backends/__init__.py",
line 134, in _cursor
return self.create_cursor()
File
"/home/user1/sme-appname/lib/python2.7/site-packages/django/db/backends/postgresql_psycopg2/base.py",
line 138, in create_cursor
cursor = self.connection.cursor()
InterfaceError: connection already closed
I posted this on psycopg2 mailing list, but was told to contact you Django
guys. Anyway, after tinkering around with some code in the django/db
directory, I generated the following "fix" that helped most of our test
cases to pass. The fix is in two files:
(1) django/db/backends/__init__.py --> comment out the code that compares
two autocommit values.
def close_if_unusable_or_obsolete(self):
"""
Closes the current connection if unrecoverable errors have occurred,
or if it outlived its maximum age.
"""
if self.connection is not None:
# If the application didn't restore the original autocommit
setting,
# don't take chances, drop the connection.
#if self.get_autocommit() != self.settings_dict['AUTOCOMMIT']:
# print("---- from within close_if_unusable_or_obsolete
method ----")
# print("---- two autocommit settings not equal ----")
# print(self.get_autocommit())
# print(self.settings_dict['AUTOCOMMIT'])
# self.close()
# return
if self.errors_occurred:
if self.is_usable():
self.errors_occurred = False
else:
print("---- from within close_if_unusable_or_obsolete
method ----")
self.close()
return
if self.close_at is not None and time.time() >= self.close_at:
print("---- from within close_if_unusable_or_obsolete
method ----")
self.close()
return
(2) django/db/__init__.py --> simply call the recommended
close_old_connections() as the comment in close_connection suggests, and
comment out the old code.
def close_connection(**kwargs):
#warnings.warn(
# "close_connection is superseded by close_old_connections.",
# PendingDeprecationWarning, stacklevel=2)
## Avoid circular imports
#from django.db import transaction
#for conn in connections:
# # If an error happens here the connection will be left in broken
# # state. Once a good db connection is again available, the
# # connection state will be cleaned up.
# transaction.abort(conn)
# print("---- from within close_connection method ----")
# connections[conn].close()
close_old_connections()
I am not a Django expert, much less a Django/db expert. Could somebody
investigate whether something like this can be done and released in Django
1.6.8? I am especially puzzled by why the two autocommit values are
different. Should I do something else (in Django test
client/settings/elsewhere) to make the two autocommit values the same? If
this "fix" helps you guys, fine; we are interested in some proper fix
coming from Django directly rather than patching things up ourselves.
Thanks,
Arun
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