49f1efc773
Add unit tests and '# pragma: no cover' for exclude some code that doesn't require test. Change-Id: Ib071208bd38c7b1102aa341be0d6bf803b647596
53 lines
1.7 KiB
Python
53 lines
1.7 KiB
Python
# Copyright (c) 2015 Mirantis, Inc.
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# All Rights Reserved.
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#
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# Licensed under the Apache License, Version 2.0 (the "License"); you may
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# not use this file except in compliance with the License. You may obtain
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# a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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# License for the specific language governing permissions and limitations
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# under the License.
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"""Utilities for database."""
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from oslo_config import cfg
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from oslo_log import log
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CONF = cfg.CONF
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LOG = log.getLogger(__name__)
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class PluggableBackend(object):
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"""A pluggable backend loaded lazily based on some value."""
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def __init__(self, pivot, **backends):
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self.__backends = backends
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self.__pivot = pivot
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self.__backend = None
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def __get_backend(self):
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if not self.__backend:
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backend_name = CONF[self.__pivot]
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if backend_name not in self.__backends: # pragma: no cover
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raise Exception('Invalid backend: %s' % backend_name)
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backend = self.__backends[backend_name]
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if isinstance(backend, tuple): # pragma: no cover
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name = backend[0]
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fromlist = backend[1]
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else:
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name = backend
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fromlist = backend
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self.__backend = __import__(name, None, None, fromlist)
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LOG.debug('backend %s', self.__backend)
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return self.__backend
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def __getattr__(self, key):
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backend = self.__get_backend()
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return getattr(backend, key)
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