[win32] fix deadlock occuring on the sequence tables with SQLServer
actually, this deadlock would occur with any db backend other that PostgreSQL
as the previous code was heavily relying on PG's SEQUENCE facility, not available
elsewhere.
Deadlock description:
Thread1 starts creating entities (and therefore calls create_eid):
-> this creates a DB-level lock on the entities_id_seq table, which
will last until end of transaction
Thread2 calls create_eid, which acquires the Python lock object, but
updating the entities_id_seq is held by the DB lock
Thread1 wants to create a new entity, calls create_eid, and is stuck by
the Python lock object held by Thread2.
Solution:
use a separate connection to read and write the entities_id_seq table.
# copyright 2003-2010 LOGILAB S.A. (Paris, FRANCE), all rights reserved.
# contact http://www.logilab.fr/ -- mailto:contact@logilab.fr
#
# This file is part of CubicWeb.
#
# CubicWeb is free software: you can redistribute it and/or modify it under the
# terms of the GNU Lesser General Public License as published by the Free
# Software Foundation, either version 2.1 of the License, or (at your option)
# any later version.
#
# CubicWeb is distributed in the hope that it will be useful, but WITHOUT
# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
# FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more
# details.
#
# You should have received a copy of the GNU Lesser General Public License along
# with CubicWeb. If not, see <http://www.gnu.org/licenses/>.
"""core hooks
"""
__docformat__ = "restructuredtext en"
from datetime import timedelta, datetime
from cubicweb.server import hook
class ServerStartupHook(hook.Hook):
"""task to cleanup expirated auth cookie entities"""
__regid__ = 'cw_cleanup_transactions'
events = ('server_startup',)
def __call__(self):
# XXX use named args and inner functions to avoid referencing globals
# which may cause reloading pb
lifetime = timedelta(days=self.repo.config['keep-transaction-lifetime'])
def cleanup_old_transactions(repo=self.repo, lifetime=lifetime):
mindate = datetime.now() - lifetime
session = repo.internal_session()
try:
session.system_sql(
'DELETE FROM transactions WHERE tx_time < %(time)s',
{'time': mindate})
# cleanup deleted entities
session.system_sql(
'DELETE FROM deleted_entities WHERE dtime < %(time)s',
{'time': mindate})
session.commit()
finally:
session.close()
self.repo.looping_task(60*60*24, cleanup_old_transactions, self.repo)