93 lines
2.9 KiB
Python
93 lines
2.9 KiB
Python
# 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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r"""
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Environment
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-----------
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The **environment** backend driver provides a method of accessing
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configuration data in environment variables. It is enabled by default
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and requires no additional configuration to use. The environment is
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checked after command line options, but before configuration files.
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Environment variables are checked for any configuration data. The variable
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names take the form:
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* A prefix of ``OS_``
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* The group name, uppercased
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* Separated from the option name by a `__` (double underscore)
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* Followed by the name
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For an option that looks like this in the usual INI format::
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[placement_database]
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connection = sqlite:///
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the corresponding environment variable would be
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``OS_PLACEMENT_DATABASE__CONNECTION``.
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The Driver Class
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================
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.. autoclass:: EnvironmentConfigurationSourceDriver
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The Configuration Source Class
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==============================
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.. autoclass:: EnvironmentConfigurationSource
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"""
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import os
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# Avoid circular import
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import oslo_config.cfg
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from oslo_config import sources
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# In current practice this class is not used because the
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# EnvironmentConfigurationSource is loaded by default, but we keep it
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# here in case we choose to change that behavior in the future.
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class EnvironmentConfigurationSourceDriver(sources.ConfigurationSourceDriver):
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"""A backend driver for environment variables.
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This configuration source is available by default and does not need special
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configuration to use. The sample config is generated automatically but is
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not necessary.
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"""
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def list_options_for_discovery(self):
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"""There are no options for this driver."""
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return []
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def open_source_from_opt_group(self, conf, group_name):
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return EnvironmentConfigurationSource()
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class EnvironmentConfigurationSource(sources.ConfigurationSource):
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"""A configuration source for options in the environment."""
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@staticmethod
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def _make_name(group_name, option_name):
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group_name = group_name or 'DEFAULT'
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return 'OS_{}__{}'.format(group_name.upper(), option_name.upper())
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def get(self, group_name, option_name, opt):
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env_name = self._make_name(group_name, option_name)
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try:
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value = os.environ[env_name]
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loc = oslo_config.cfg.LocationInfo(
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oslo_config.cfg.Locations.environment, env_name)
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return (value, loc)
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except KeyError:
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return (sources._NoValue, None)
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