old_contents: # vim: tabstop=4 shiftwidth=4 softtabstop=4
  
  # 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 sqlalchemy import create_engine
  from sqlalchemy.orm import sessionmaker
  
  from nova import flags
  
  FLAGS = flags.FLAGS
  
  _ENGINE = None
  _MAKER = None
  
  
  def get_session(autocommit=True, expire_on_commit=False):
      """Helper method to grab session"""
      global _ENGINE
      global _MAKER
      if not _MAKER:
          if not _ENGINE:
              _ENGINE = create_engine(FLAGS.sql_connection, echo=False)
          _MAKER = (sessionmaker(bind=_ENGINE,
                                  autocommit=autocommit,
                                  expire_on_commit=expire_on_commit))
      session = _MAKER()
      return session
  
new_contents: # vim: tabstop=4 shiftwidth=4 softtabstop=4
  
  # 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 sqlalchemy import create_engine
  from sqlalchemy.orm import sessionmaker
  
  from nova import flags
  
  FLAGS = flags.FLAGS
  
  _ENGINE = None
  _MAKER = None
  
  
  def get_session(autocommit=True, expire_on_commit=False):
      """Helper method to grab session"""
      global _ENGINE
      global _MAKER
      if not _MAKER:
          if not _ENGINE:
              _ENGINE = create_engine(FLAGS.sql_connection, pool_recycle=3600, echo=False)
          _MAKER = (sessionmaker(bind=_ENGINE,
                                  autocommit=autocommit,
                                  expire_on_commit=expire_on_commit))
      session = _MAKER()
      return session
  
subject: Add the pool_recycle setting to enable connection pooling features for the sql engine. The setting is hard-coded to 3600 seconds (one hour) per the recommendation provided on sqlalchemy's site