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# Copyright 2014 Rackspace
# Licensed under the Apache License, Version 2.0 (the "License"); you may
# not use this file except in compliance with the License. You may obtain
# a copy of the License at
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
# License for the specific language governing permissions and limitations
# under the License.
import contextlib
import time
from sqlalchemy.sql.expression import select
from oslo_config import cfg
from oslo_db.sqlalchemy import session as db_session
from oslo_log import log as logging
from oslo_utils import excutils
LOG = logging.getLogger(__name__)
_FACADE = None
def _create_facade_lazily():
global _FACADE
if _FACADE is None:
_FACADE = db_session.EngineFacade.from_config(cfg.CONF, sqlite_fk=True)
return _FACADE
def get_engine():
facade = _create_facade_lazily()
return facade.get_engine()
def get_session(expire_on_commit=True, autocommit=True):
"""Helper method to grab session."""
facade = _create_facade_lazily()
return facade.get_session(expire_on_commit=expire_on_commit,
def get_lock_session():
"""Context manager for using a locking (not auto-commit) session."""
lock_session = get_session(autocommit=False)
yield lock_session
except Exception:
with excutils.save_and_reraise_exception():
def wait_for_connection(exit_event):
"""Helper method to wait for DB connection"""
down = True
while down and not exit_event.is_set():
LOG.debug('Trying to re-establish connection to database.')
down = False
LOG.debug('Connection to database re-established.')
except Exception:
retry_interval = cfg.CONF.database.retry_interval
LOG.exception('Connection to database failed. Retrying in %s '
'seconds.', retry_interval)