ec2-api/ec2api/db/migration.py

77 lines
2.4 KiB
Python

# Copyright 2013 Cloudscaling Group, Inc
#
# 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.
"""Database setup and migration commands."""
from oslo_config import cfg
from ec2api import exception
from ec2api.i18n import _
CONF = cfg.CONF
class LazyPluggable(object):
"""A pluggable backend loaded lazily based on some value."""
def __init__(self, pivot, config_group=None, **backends):
self.__backends = backends
self.__pivot = pivot
self.__backend = None
self.__config_group = config_group
def __get_backend(self):
if not self.__backend:
if self.__config_group is None:
backend_name = CONF[self.__pivot]
else:
backend_name = CONF[self.__config_group][self.__pivot]
if backend_name not in self.__backends:
msg = _('Invalid backend: %s') % backend_name
raise exception.EC2Exception(msg)
backend = self.__backends[backend_name]
if isinstance(backend, tuple):
name = backend[0]
fromlist = backend[1]
else:
name = backend
fromlist = backend
self.__backend = __import__(name, None, None, fromlist)
return self.__backend
def __getattr__(self, key):
backend = self.__get_backend()
return getattr(backend, key)
IMPL = LazyPluggable('backend',
config_group='database',
sqlalchemy='ec2api.db.sqlalchemy.migration')
def db_sync(version=None):
"""Migrate the database to `version` or the most recent version."""
return IMPL.db_sync(version=version)
def db_version():
"""Display the current database version."""
return IMPL.db_version()
def db_initial_version():
"""The starting version for the database."""
return IMPL.db_initial_version()