126 lines
4.4 KiB
Python
126 lines
4.4 KiB
Python
# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain 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,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
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# implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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import sys
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from oslo_concurrency import lockutils
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from oslo_log import log as logging
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from oslo_utils import importutils
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from stevedore import driver
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from stevedore import enabled
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from neutron_lib._i18n import _
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LOG = logging.getLogger(__name__)
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SYNCHRONIZED_PREFIX = 'neutron-'
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# common synchronization decorator
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synchronized = lockutils.synchronized_with_prefix(SYNCHRONIZED_PREFIX)
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class NamespacedPlugins(object):
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"""Wraps a stevedore plugin namespace to load/access its plugins."""
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def __init__(self, namespace):
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self.namespace = namespace
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self._extension_manager = None
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self._extensions = {}
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self.reload()
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def reload(self):
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"""Force a reload of the plugins for this instances namespace.
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:returns: None.
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"""
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self._extensions = {}
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self._extension_manager = enabled.EnabledExtensionManager(
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self.namespace, lambda x: True,
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invoke_on_load=False)
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if not self._extension_manager.names():
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LOG.debug("No plugins found in namespace: ", self.namespace)
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return
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self._extension_manager.map(self._add_extension)
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def _add_extension(self, ext):
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if ext.name in self._extensions:
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msg = _("Plugin '%(p)s' already in namespace: %(ns)s") % {
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'p': ext.name, 'ns': self.namespace}
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raise KeyError(msg)
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LOG.debug("Loaded plugin '%s' from namespace: %s",
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ext.name, self.namespace)
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self._extensions[ext.name] = ext
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def _assert_plugin_loaded(self, plugin_name):
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if plugin_name not in self._extensions:
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msg = _("Plugin '%(p)s' not in namespace: %(ns)s") % {
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'p': plugin_name, 'ns': self.namespace}
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raise KeyError(msg)
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def get_plugin_class(self, plugin_name):
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"""Gets a reference to a loaded plugin's class.
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:param plugin_name: The name of the plugin to get the class for.
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:returns: A reference to the loaded plugin's class.
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:raises: KeyError if plugin_name is not loaded.
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"""
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self._assert_plugin_loaded(plugin_name)
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return self._extensions[plugin_name].plugin
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def new_plugin_instance(self, plugin_name, *args, **kwargs):
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"""Create a new instance of a plugin.
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:param plugin_name: The name of the plugin to instantiate.
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:param args: Any args to pass onto the constructor.
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:param kwargs: Any kwargs to pass onto the constructor.
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:returns: A new instance of plugin_name.
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:raises: KeyError if plugin_name is not loaded.
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"""
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self._assert_plugin_loaded(plugin_name)
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return self.get_plugin_class(plugin_name)(*args, **kwargs)
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@property
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def loaded_plugin_names(self):
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return self._extensions.keys()
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def load_class_by_alias_or_classname(namespace, name):
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"""Load a class using stevedore alias or the class name.
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:param namespace: The namespace where the alias is defined.
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:param name: The alias or class name of the class to be loaded.
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:returns: Class if it can be loaded.
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:raises ImportError: if class cannot be loaded.
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"""
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if not name:
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LOG.error("Alias or class name is not set")
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raise ImportError(_("Class not found."))
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try:
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# Try to resolve class by alias
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mgr = driver.DriverManager(
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namespace, name, warn_on_missing_entrypoint=False)
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class_to_load = mgr.driver
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except RuntimeError:
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e1_info = sys.exc_info()
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# Fallback to class name
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try:
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class_to_load = importutils.import_class(name)
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except (ImportError, ValueError):
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LOG.error("Error loading class by alias",
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exc_info=e1_info)
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LOG.error("Error loading class by class name",
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exc_info=True)
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raise ImportError(_("Class not found."))
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return class_to_load
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