107 lines
3.7 KiB
Python
107 lines
3.7 KiB
Python
# vim: tabstop=4 shiftwidth=4 softtabstop=4
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# Copyright (c) 2013 Rackspace Hosting
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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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"""Multiple DB API backend support.
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Supported configuration options:
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The following two parameters are in the 'database' group:
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`backend`: DB backend name or full module path to DB backend module.
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`use_tpool`: Enable thread pooling of DB API calls.
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A DB backend module should implement a method named 'get_backend' which
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takes no arguments. The method can return any object that implements DB
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API methods.
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*NOTE*: There are bugs in eventlet when using tpool combined with
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threading locks. The python logging module happens to use such locks. To
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work around this issue, be sure to specify thread=False with
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eventlet.monkey_patch().
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A bug for eventlet has been filed here:
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https://bitbucket.org/eventlet/eventlet/issue/137/
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"""
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import functools
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from oslo.config import cfg
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from storyboard.openstack.common import importutils
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from storyboard.openstack.common import lockutils
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db_opts = [
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cfg.StrOpt('backend',
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default='sqlalchemy',
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deprecated_name='db_backend',
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deprecated_group='DEFAULT',
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help='The backend to use for db'),
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cfg.BoolOpt('use_tpool',
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default=False,
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deprecated_name='dbapi_use_tpool',
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deprecated_group='DEFAULT',
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help='Enable the experimental use of thread pooling for '
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'all DB API calls')
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]
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CONF = cfg.CONF
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CONF.register_opts(db_opts, 'database')
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class DBAPI(object):
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def __init__(self, backend_mapping=None):
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if backend_mapping is None:
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backend_mapping = {}
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self.__backend = None
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self.__backend_mapping = backend_mapping
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@lockutils.synchronized('dbapi_backend', 'storyboard-')
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def __get_backend(self):
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"""Get the actual backend. May be a module or an instance of
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a class. Doesn't matter to us. We do this synchronized as it's
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possible multiple greenthreads started very quickly trying to do
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DB calls and eventlet can switch threads before self.__backend gets
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assigned.
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"""
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if self.__backend:
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# Another thread assigned it
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return self.__backend
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backend_name = CONF.database.backend
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self.__use_tpool = CONF.database.use_tpool
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if self.__use_tpool:
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from eventlet import tpool
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self.__tpool = tpool
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# Import the untranslated name if we don't have a
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# mapping.
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backend_path = self.__backend_mapping.get(backend_name,
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backend_name)
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backend_mod = importutils.import_module(backend_path)
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self.__backend = backend_mod.get_backend()
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return self.__backend
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def __getattr__(self, key):
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backend = self.__backend or self.__get_backend()
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attr = getattr(backend, key)
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if not self.__use_tpool or not hasattr(attr, '__call__'):
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return attr
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def tpool_wrapper(*args, **kwargs):
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return self.__tpool.execute(attr, *args, **kwargs)
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functools.update_wrapper(tpool_wrapper, attr)
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return tpool_wrapper
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