text: # Copyright 2010 United States Government as represented by the
  #   Administrator of the National Aeronautics and Space Administration.
  #   All Rights Reserved.
  #
  # 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.
  
  """Session Handling for SQLAlchemy backend."""
  
  from oslo.config import cfg
  from oslo_db.sqlalchemy import session
  from oslo_log import log as logging
  
  
  LOG = logging.getLogger(__name__)
  
  CONF = cfg.CONF
  
  
  _FACADES = {}
  
  
  def _create_facade_lazily(cfg_group, connection=None, discriminator=None):
      connection = connection or cfg.CONF[cfg_group].connection
      cache_name = "%s:%s" % (cfg_group, discriminator)
  
      if cache_name not in _FACADES:
          _FACADES[cache_name] = session.EngineFacade(
              connection,
              **dict(cfg.CONF[cfg_group].iteritems()))
  
      return _FACADES[cache_name]
  
  
  def get_engine(cfg_group):
      facade = _create_facade_lazily(cfg_group)
      return facade.get_engine()
  
  
  def get_session(cfg_group, connection=None, discriminator=None, **kwargs):
      facade = _create_facade_lazily(cfg_group, connection, discriminator)
      return facade.get_session(**kwargs)
  