146 lines
5.8 KiB
Python
146 lines
5.8 KiB
Python
# Copyright 2013 Red Hat, Inc.
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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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from oslo_concurrency import lockutils
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from oslo_config import cfg
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from oslo_log import log
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from stevedore import dispatch
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from ironic.common import exception
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from ironic.common.i18n import _
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from ironic.common.i18n import _LI
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LOG = log.getLogger(__name__)
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driver_opts = [
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cfg.ListOpt('enabled_drivers',
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default=['pxe_ipmitool'],
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help=_('Specify the list of drivers to load during service '
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'initialization. Missing drivers, or drivers which '
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'fail to initialize, will prevent the conductor '
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'service from starting. The option default is a '
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'recommended set of production-oriented drivers. A '
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'complete list of drivers present on your system may '
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'be found by enumerating the "ironic.drivers" '
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'entrypoint. An example may be found in the '
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'developer documentation online.')),
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]
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CONF = cfg.CONF
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CONF.register_opts(driver_opts)
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EM_SEMAPHORE = 'extension_manager'
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def get_driver(driver_name):
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"""Simple method to get a ref to an instance of a driver.
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Driver loading is handled by the DriverFactory class. This method
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conveniently wraps that class and returns the actual driver object.
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:param driver_name: the name of the driver class to load
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:returns: An instance of a class which implements
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ironic.drivers.base.BaseDriver
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:raises: DriverNotFound if the requested driver_name could not be
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found in the "ironic.drivers" namespace.
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"""
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try:
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factory = DriverFactory()
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return factory[driver_name].obj
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except KeyError:
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raise exception.DriverNotFound(driver_name=driver_name)
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def drivers():
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"""Get all drivers as a dict name -> driver object."""
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factory = DriverFactory()
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return {name: factory[name].obj for name in factory.names}
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class DriverFactory(object):
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"""Discover, load and manage the drivers available."""
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# NOTE(deva): loading the _extension_manager as a class member will break
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# stevedore when it loads a driver, because the driver will
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# import this file (and thus instantiate another factory).
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# Instead, we instantiate a NameDispatchExtensionManager only
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# once, the first time DriverFactory.__init__ is called.
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_extension_manager = None
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def __init__(self):
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if not DriverFactory._extension_manager:
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DriverFactory._init_extension_manager()
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def __getitem__(self, name):
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return self._extension_manager[name]
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# NOTE(deva): Use lockutils to avoid a potential race in eventlet
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# that might try to create two driver factories.
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@classmethod
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@lockutils.synchronized(EM_SEMAPHORE, 'ironic-')
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def _init_extension_manager(cls):
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# NOTE(deva): In case multiple greenthreads queue up on this lock
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# before _extension_manager is initialized, prevent
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# creation of multiple NameDispatchExtensionManagers.
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if cls._extension_manager:
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return
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# NOTE(deva): Drivers raise "DriverLoadError" if they are unable to be
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# loaded, eg. due to missing external dependencies.
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# We capture that exception, and, only if it is for an
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# enabled driver, raise it from here. If enabled driver
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# raises other exception type, it is wrapped in
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# "DriverLoadError", providing the name of the driver that
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# caused it, and raised. If the exception is for a
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# non-enabled driver, we suppress it.
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def _catch_driver_not_found(mgr, ep, exc):
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# NOTE(deva): stevedore loads plugins *before* evaluating
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# _check_func, so we need to check here, too.
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if ep.name in CONF.enabled_drivers:
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if not isinstance(exc, exception.DriverLoadError):
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raise exception.DriverLoadError(driver=ep.name, reason=exc)
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raise exc
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def _check_func(ext):
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return ext.name in CONF.enabled_drivers
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cls._extension_manager = (
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dispatch.NameDispatchExtensionManager(
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'ironic.drivers',
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_check_func,
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invoke_on_load=True,
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on_load_failure_callback=_catch_driver_not_found))
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# NOTE(deva): if we were unable to load any configured driver, perhaps
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# because it is not present on the system, raise an error.
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if (sorted(CONF.enabled_drivers) !=
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sorted(cls._extension_manager.names())):
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found = cls._extension_manager.names()
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names = [n for n in CONF.enabled_drivers if n not in found]
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# just in case more than one could not be found ...
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names = ', '.join(names)
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raise exception.DriverNotFound(driver_name=names)
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LOG.info(_LI("Loaded the following drivers: %s"),
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cls._extension_manager.names())
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@property
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def names(self):
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"""The list of driver names available."""
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return self._extension_manager.names()
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