OpenStack Orchestration (Heat)
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# vim: tabstop=4 shiftwidth=4 softtabstop=4
# 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.
"""Session Handling for SQLAlchemy backend."""
import logging
import sqlalchemy.interfaces
import sqlalchemy.orm
from sqlalchemy.exc import DisconnectionError
from heat.db import api as db_api
from heat.openstack.common import cfg
logger = logging.getLogger('heat.db.sqlalchemy.session')
_ENGINE = None
_MAKER = None
def get_session(autocommit=True, expire_on_commit=False):
"""Return a SQLAlchemy session."""
global _ENGINE, _MAKER
if _MAKER is None or _ENGINE is None:
_ENGINE = get_engine()
_MAKER = get_maker(_ENGINE, autocommit, expire_on_commit)
return _MAKER()
class SynchronousSwitchListener(sqlalchemy.interfaces.PoolListener):
"""Switch sqlite connections to non-synchronous mode"""
def connect(self, dbapi_con, con_record):
dbapi_con.execute("PRAGMA synchronous = OFF")
class MySQLPingListener(object):
Ensures that MySQL connections checked out of the
pool are alive.
Borrowed from:
def checkout(self, dbapi_con, con_record, con_proxy):
dbapi_con.cursor().execute('select 1')
except dbapi_con.OperationalError, ex:
if ex.args[0] in (2006, 2013, 2014, 2045, 2055):
logger.warn('Got mysql server has gone away: %s', ex)
raise DisconnectionError("Database server went away")
def get_engine():
"""Return a SQLAlchemy engine."""
connection_dict = sqlalchemy.engine.url.make_url(_get_sql_connection())
engine_args = {
"pool_recycle": _get_sql_idle_timeout(),
"echo": False,
'convert_unicode': True,
if 'mysql' in connection_dict.drivername:
engine_args['listeners'] = [MySQLPingListener()]
return sqlalchemy.create_engine(_get_sql_connection(), **engine_args)
def get_maker(engine, autocommit=True, expire_on_commit=False):
"""Return a SQLAlchemy sessionmaker using the given engine."""
ses = sqlalchemy.orm.sessionmaker(bind=engine,
return sqlalchemy.orm.scoped_session(ses)
def _get_sql_connection():
return db_api.SQL_CONNECTION
def _get_sql_idle_timeout():
return db_api.SQL_IDLE_TIMEOUT