/
api.py
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/
api.py
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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
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# 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 time
from sqlalchemy.sql.expression import select
from oslo_config import cfg
from oslo_db.sqlalchemy import enginefacade
from oslo_log import log as logging
LOG = logging.getLogger(__name__)
_FACADE = None
def _create_facade_lazily():
global _FACADE
if _FACADE is None:
_FACADE = True
enginefacade.configure(sqlite_fk=True, expire_on_commit=True)
def _get_transaction_context(reader=False):
_create_facade_lazily()
# TODO(gthiemonge) Create and use new functions to get read-only sessions
if reader:
context = enginefacade.reader
else:
context = enginefacade.writer
return context
def _get_sessionmaker(reader=False):
context = _get_transaction_context(reader)
return context.get_sessionmaker()
def get_engine():
context = _get_transaction_context()
return context.get_engine()
def get_session():
"""Helper method to grab session."""
return _get_sessionmaker()()
def session():
return _get_sessionmaker()
def wait_for_connection(exit_event):
"""Helper method to wait for DB connection"""
down = True
while down and not exit_event.is_set():
try:
LOG.debug('Trying to re-establish connection to database.')
get_engine().scalar(select([1]))
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)
time.sleep(retry_interval)