[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.
# pylint: disable-msg=W0401,W0614
# 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/>.
"""exceptions used in the core of the CubicWeb web application
"""
__docformat__ = "restructuredtext en"
from cubicweb._exceptions import *
class PublishException(CubicWebException):
"""base class for publishing related exception"""
class RequestError(PublishException):
"""raised when a request can't be served because of a bad input"""
class NothingToEdit(RequestError):
"""raised when an edit request doesn't specify any eid to edit"""
class ProcessFormError(RequestError):
"""raised when posted data can't be processed by the corresponding field
"""
class NotFound(RequestError):
"""raised when a 404 error should be returned"""
class Redirect(PublishException):
"""raised to redirect the http request"""
def __init__(self, location):
self.location = location
class DirectResponse(Exception):
def __init__(self, response):
self.response = response
class StatusResponse(Exception):
def __init__(self, status, content=''):
self.status = int(status)
self.content = content
class InvalidSession(CubicWebException):
"""raised when a session id is found but associated session is not found or
invalid
"""
class RemoteCallFailed(RequestError):
"""raised when a json remote call fails
"""
def __init__(self, reason=''):
super(RequestError, self).__init__()
self.reason = reason
def dumps(self):
from cubicweb.web import json
return json.dumps({'reason': self.reason})
class LogOut(PublishException):
"""raised to ask for deauthentication of a logged in user"""
def __init__(self, url):
super(LogOut, self).__init__()
self.url = url