text: #    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.
  
  from __future__ import with_statement
  from logging import config as logging_config
  import sys
  
  from alembic import context
  from sqlalchemy import create_engine
  from sqlalchemy import pool
  # this is the Alembic Config object, which provides
  # access to the values within the .ini file in use.
  config = context.config
  try:
      octavia_config = config.octavia_config
  except AttributeError:
      print("Error: Please use the octavia-db-manage command for octavia"
            " alembic actions.")
      sys.exit(1)
  
  # Interpret the config file for Python logging.
  # This line sets up loggers basically.
  logging_config.fileConfig(config.config_file_name)
  
  # add your model's MetaData object here
  # for 'autogenerate' support
  # from myapp import mymodel
  # target_metadata = mymodel.Base.metadata
  target_metadata = None
  
  # other values from the config, defined by the needs of env.py,
  # can be acquired:
  # my_important_option = config.get_main_option("my_important_option")
  # ... etc.
  
  
  def run_migrations_offline():
      """Run migrations in 'offline' mode.
  
      This configures the context with just a URL
      and not an Engine, though an Engine is acceptable
      here as well.  By skipping the Engine creation
      we don't even need a DBAPI to be available.
  
      Calls to context.execute() here emit the given string to the
      script output.
  
      """
      context.configure(url=octavia_config.database.connection,
                        target_metadata=target_metadata)
  
      with context.begin_transaction():
          context.run_migrations()
  
  
  def run_migrations_online():
      """Run migrations in 'online' mode.
  
      In this scenario we need to create an Engine
      and associate a connection with the context.
  
      """
      engine = create_engine(
          octavia_config.database.connection,
          poolclass=pool.NullPool)
  
      connection = engine.connect()
      context.configure(
          connection=connection,
          target_metadata=target_metadata)
  
      try:
          with context.begin_transaction():
              context.run_migrations()
      finally:
          connection.close()
  
  if context.is_offline_mode():
      run_migrations_offline()
  else:
      run_migrations_online()
  