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OpenStack Study: api.py**** CubicPower OpenStack Study ****
# vim: tabstop=4 shiftwidth=4 softtabstop=4 # Copyright (c) 2013 Rackspace Hosting # All Rights Reserved. # # Licensed under the Apache License, Version 2.0 (the "License"); you may # not use this file except in compliance with the License. You may obtain # a copy of the License at # # http://www.apache.org/licenses/LICENSE-2.0 # # Unless required by applicable law or agreed to in writing, software # distributed under the License is distributed on an "AS IS" BASIS, WITHOUT # WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the # License for the specific language governing permissions and limitations # under the License. """Multiple DB API backend support. Supported configuration options: The following two parameters are in the 'database' group: `backend`: DB backend name or full module path to DB backend module. `use_tpool`: Enable thread pooling of DB API calls. A DB backend module should implement a method named 'get_backend' which takes no arguments. The method can return any object that implements DB API methods. *NOTE*: There are bugs in eventlet when using tpool combined with threading locks. The python logging module happens to use such locks. To work around this issue, be sure to specify thread=False with eventlet.monkey_patch(). A bug for eventlet has been filed here: https://bitbucket.org/eventlet/eventlet/issue/137/ """ import functools from oslo.config import cfg from cinder.openstack.common import importutils from cinder.openstack.common import lockutils db_opts = [ cfg.StrOpt('backend', default='sqlalchemy', deprecated_name='db_backend', deprecated_group='DEFAULT', help='The backend to use for db'), cfg.BoolOpt('use_tpool', default=False, deprecated_name='dbapi_use_tpool', deprecated_group='DEFAULT', help='Enable the experimental use of thread pooling for ' 'all DB API calls') ] CONF = cfg.CONF CONF.register_opts(db_opts, 'database')
**** CubicPower OpenStack Study **** class DBAPI(object):
**** CubicPower OpenStack Study **** def __init__(self, backend_mapping=None): if backend_mapping is None: backend_mapping = {} self.__backend = None self.__backend_mapping = backend_mapping @lockutils.synchronized('dbapi_backend', 'cinder-')
**** CubicPower OpenStack Study **** def __get_backend(self): """Get the actual backend. May be a module or an instance of a class. Doesn't matter to us. We do this synchronized as it's possible multiple greenthreads started very quickly trying to do DB calls and eventlet can switch threads before self.__backend gets assigned. """ if self.__backend: # Another thread assigned it return self.__backend backend_name = CONF.database.backend self.__use_tpool = CONF.database.use_tpool if self.__use_tpool: from eventlet import tpool self.__tpool = tpool # Import the untranslated name if we don't have a # mapping. backend_path = self.__backend_mapping.get(backend_name, backend_name) backend_mod = importutils.import_module(backend_path) self.__backend = backend_mod.get_backend() return self.__backend
**** CubicPower OpenStack Study **** def __getattr__(self, key): backend = self.__backend or self.__get_backend() attr = getattr(backend, key) if not self.__use_tpool or not hasattr(attr, '__call__'): return attr def tpool_wrapper(*args, **kwargs): return self.__tpool.execute(attr, *args, **kwargs) functools.update_wrapper(tpool_wrapper, attr) return tpool_wrapper
**** CubicPower OpenStack Study **** def tpool_wrapper(*args, **kwargs): return self.__tpool.execute(attr, *args, **kwargs) functools.update_wrapper(tpool_wrapper, attr) return tpool_wrapper
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