46d30eeb29
Also fixes up some inline-code/examples docs to correctly display in the generated docs (and tweaks some URI capitalization). Change-Id: I001ef2460eb5e9a884ca6db6e8d6f72864191fe7
93 lines
3.5 KiB
Python
93 lines
3.5 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 six
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from stevedore import driver
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from taskflow import exceptions as exc
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from taskflow import logging
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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 URI's components, 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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if isinstance(conf, six.string_types):
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conf = {'connection': conf}
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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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# If the backend is like 'mysql+pymysql://...' which informs the
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# backend to use a dialect (supported by sqlalchemy at least) we just want
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# to look at the first component to find our entrypoint backend name...
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if backend_name.find("+") != -1:
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backend_name = backend_name.split("+", 1)[0]
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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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