164 lines
5.6 KiB
Python
164 lines
5.6 KiB
Python
# Copyright (c) 2012 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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"""Configuration support for all drivers.
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This module allows support for setting configurations either from default
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or from a particular FLAGS group, to be able to set multiple configurations
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for a given set of values.
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For instance, two lvm configurations can be set by naming them in groups as
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[lvm1]
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volume_group=lvm-group-1
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...
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[lvm2]
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volume_group=lvm-group-2
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...
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And the configuration group name will be passed in so that all calls to
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configuration.volume_group within that instance will be mapped to the proper
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named group.
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This class also ensures the implementation's configuration is grafted into the
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option group. This is due to the way cfg works. All cfg options must be defined
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and registered in the group in which they are used.
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"""
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from oslo_config import cfg
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CONF = cfg.CONF
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SHARED_CONF_GROUP = 'backend_defaults'
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class DefaultGroupConfiguration(object):
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"""Get config options from only DEFAULT."""
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def __init__(self):
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# set the local conf so that __call__'s know what to use
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self.local_conf = CONF
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def _ensure_config_values(self, volume_opts):
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CONF.register_opts(volume_opts, group=None)
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def append_config_values(self, volume_opts):
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self._ensure_config_values(volume_opts)
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def safe_get(self, value):
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try:
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return self.__getattr__(value)
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except cfg.NoSuchOptError:
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return None
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def __getattr__(self, value):
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# Don't use self.local_conf to avoid reentrant call to __getattr__()
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local_conf = object.__getattribute__(self, 'local_conf')
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return getattr(local_conf, value)
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class BackendGroupConfiguration(object):
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def __init__(self, volume_opts, config_group=None):
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"""Initialize configuration.
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This takes care of grafting the implementation's config
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values into the config group and shared defaults. We will try to
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pull values from the specified 'config_group', but fall back to
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defaults from the SHARED_CONF_GROUP.
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"""
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self.config_group = config_group
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# set the local conf so that __call__'s know what to use
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self._ensure_config_values(volume_opts)
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self.backend_conf = CONF._get(self.config_group)
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self.shared_backend_conf = CONF._get(SHARED_CONF_GROUP)
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def _safe_register(self, opt, group):
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try:
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CONF.register_opt(opt, group=group)
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except cfg.DuplicateOptError:
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pass # If it's already registered ignore it
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def _ensure_config_values(self, volume_opts):
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"""Register the options in the shared group.
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When we go to get a config option we will try the backend specific
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group first and fall back to the shared group. We override the default
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from all the config options for the backend group so we can know if it
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was set or not.
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"""
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for opt in volume_opts:
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self._safe_register(opt, SHARED_CONF_GROUP)
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# Assuming they aren't the same groups, graft on the options into
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# the backend group and override its default value.
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if self.config_group != SHARED_CONF_GROUP:
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self._safe_register(opt, self.config_group)
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CONF.set_default(opt.name, None, group=self.config_group)
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def append_config_values(self, volume_opts):
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self._ensure_config_values(volume_opts)
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def set_default(self, opt_name, default):
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CONF.set_default(opt_name, default, group=SHARED_CONF_GROUP)
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def get(self, key, default=None):
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return getattr(self, key, default)
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def safe_get(self, value):
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try:
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return self.__getattr__(value)
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except cfg.NoSuchOptError:
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return None
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def __getattr__(self, opt_name):
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# Don't use self.X to avoid reentrant call to __getattr__()
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backend_conf = object.__getattribute__(self, 'backend_conf')
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opt_value = getattr(backend_conf, opt_name)
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if opt_value is None:
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shared_conf = object.__getattribute__(self, 'shared_backend_conf')
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opt_value = getattr(shared_conf, opt_name)
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return opt_value
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class Configuration(object):
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def __init__(self, volume_opts, config_group=None):
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"""Initialize configuration.
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This shim will allow for compatibility with the DEFAULT
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style of backend configuration which is used by some of the users
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of this configuration helper, or by the volume drivers that have
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all been forced over to the config_group style.
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"""
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self.config_group = config_group
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if config_group:
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self.conf = BackendGroupConfiguration(volume_opts, config_group)
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else:
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self.conf = DefaultGroupConfiguration()
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def append_config_values(self, volume_opts):
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self.conf.append_config_values(volume_opts)
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def safe_get(self, value):
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return self.conf.safe_get(value)
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def __getattr__(self, value):
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# Don't use self.conf to avoid reentrant call to __getattr__()
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conf = object.__getattribute__(self, 'conf')
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return getattr(conf, value)
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