7fe6bf0d6b
In order to make it simpler (and less code) just prefer to use object types that already exist instead of trying to make dictionaries also behave like objects. For those that really need this kind of functionality: https://pypi.python.org/pypi/attrdict Change-Id: Ib7ddfa517f0500082fafac2c3e53fd6a158a6ddf
85 lines
3.1 KiB
Python
85 lines
3.1 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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from stevedore import driver
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from taskflow import exceptions as exc
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from taskflow.utils import misc
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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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LOG = logging.getLogger(__name__)
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def fetch(conf, namespace=BACKEND_NAMESPACE, **kwargs):
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"""Fetch a persistence backend with the given configuration.
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This fetch method will look for the entrypoint name in the entrypoint
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namespace, and then attempt to instantiate that entrypoint using the
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provided configuration and any persistence backend specific kwargs.
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NOTE(harlowja): to aid in making it easy to specify configuration and
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options to a backend the configuration (which is typical just a dictionary)
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can also be a uri string that identifies the entrypoint name and any
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configuration specific to that backend.
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For example, given the following configuration uri:
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mysql://<not-used>/?a=b&c=d
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This will look for the entrypoint named 'mysql' and will provide
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a configuration object composed of the uris parameters, in this case that
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is {'a': 'b', 'c': 'd'} to the constructor of that persistence backend
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instance.
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"""
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backend_name = conf['connection']
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try:
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uri = misc.parse_uri(backend_name)
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except (TypeError, ValueError):
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pass
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else:
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backend_name = uri.scheme
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conf = misc.merge_uri(uri, conf.copy())
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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 backend, connects, upgrades, then closes it on completion.
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This allows a backend instance to be fetched, connected to, have its schema
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upgraded (if the schema is already up to date this is a no-op) and then
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used in a context manager statement with the backend being closed upon
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context manager exit.
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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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