e630907563
Allow the persistence backends to be fetched using a new helper method that can be used as a context manager, it will fetch the backend, ensure it's upgraded and upon context manager exit will close the backend automatically. Change-Id: I1bf8e43dcce25c02823cca92e3e7ed3ef254a847
68 lines
2.3 KiB
Python
68 lines
2.3 KiB
Python
# -*- coding: utf-8 -*-
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# Copyright (C) 2013 Rackspace Hosting Inc. 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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import contextlib
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import logging
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import re
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from stevedore import driver
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from taskflow import exceptions as exc
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# NOTE(harlowja): this is the entrypoint namespace, not the module namespace.
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BACKEND_NAMESPACE = 'taskflow.persistence'
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# NOTE(imelnikov): regular expression to get scheme from URI,
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# see RFC 3986 section 3.1
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SCHEME_REGEX = re.compile(r"^([A-Za-z]{1}[A-Za-z0-9+.-]*):")
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LOG = logging.getLogger(__name__)
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def fetch(conf, namespace=BACKEND_NAMESPACE, **kwargs):
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"""Fetches a given backend using the given configuration (and any backend
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specific kwargs) in the given entrypoint namespace.
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"""
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connection = conf['connection']
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match = SCHEME_REGEX.match(connection)
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if match:
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backend_name = match.group(1)
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else:
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backend_name = connection
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LOG.debug('Looking for %r backend driver in %r', backend_name, namespace)
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try:
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mgr = driver.DriverManager(namespace, backend_name,
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invoke_on_load=True,
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invoke_args=(conf,),
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invoke_kwds=kwargs)
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return mgr.driver
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except RuntimeError as e:
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raise exc.NotFound("Could not find backend %s: %s" % (backend_name, e))
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@contextlib.contextmanager
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def backend(conf, namespace=BACKEND_NAMESPACE, **kwargs):
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"""Fetches a persistence backend, ensures that it is upgraded and upon
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context manager completion closes the backend.
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"""
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with contextlib.closing(fetch(conf, namespace=namespace, **kwargs)) as be:
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with contextlib.closing(be.get_connection()) as conn:
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conn.upgrade()
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yield be
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