text: # Copyright 2012 New Dream Network, LLC (DreamHost)
  #
  #    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 logging import config as logging_config
  
  from alembic import context
  from sqlalchemy import create_engine, pool
  
  from tacker.db import model_base
  
  
  # this is the Alembic Config object, which provides
  # access to the values within the .ini file in use.
  config = context.config
  tacker_config = config.tacker_config
  
  # Interpret the config file for Python logging.
  # This line sets up loggers basically.
  logging_config.fileConfig(config.config_file_name)
  
  # set the target for 'autogenerate' support
  target_metadata = model_base.BASE.metadata
  
  
  def run_migrations_offline():
      """Run migrations in 'offline' mode.
  
      This configures the context with either a URL
      or an Engine.
  
      Calls to context.execute() here emit the given string to the
      script output.
  
      """
      kwargs = dict()
      if tacker_config.database.connection:
          kwargs['url'] = tacker_config.database.connection
      else:
          kwargs['dialect_name'] = tacker_config.database.engine
      context.configure(**kwargs)
  
      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(
          tacker_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()
  