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