I am in the process of implementing a custom weigher class. I have created a weigher that prefers hosts which do not have other instances in the same group (think GroupAntiAffinityFilter but for weight).
Here is the code for the class: # Copyright (c) 2011 OpenStack Foundation # 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 """ AntiAffinityWeigher. Weigh hosts by whether or not they have another host in the same group. """ from oslo.config import cfg from nova import db from nova.openstack.common.gettextutils import _ from nova.scheduler import weights from nova.scheduler import filters from nova.openstack.common import log as logging LOG = logging.getLogger(__name__) anti_affinity_weight_opts = [ cfg.FloatOpt('antiAffinityWeigher_Multiplier', default=1000.0, help='Multiplier used for weighing hosts. Negative ' 'numbers mean to stack vs spread.'), ] CONF = cfg.CONF CONF.register_opts(anti_affinity_weight_opts) class AntiAffinityWeigher(weights.BaseHostWeigher): def _weight_multiplier(self): """Override the weight multiplier.""" return CONF.antiAffinityWeigher_Multiplier def _weigh_object(self, host_state, weight_properties): group_hosts = weight_properties.get('group_hosts') or [] LOG.debug(_("Group anti affinity Weigher: check if %(host)s not " "in %(configured)s"), {'host': host_state.host, 'configured': group_hosts}) if group_hosts: return group_hosts.amount() * 100000 # No groups configured return 0 I know the python is at least close to correct because the scheduler service wouldn't even restart until it was. After I got the bugs worked out of the module, I added modified the /etc/nova/nova.conf file to have the custom weigher like so: scheduler_weight_classes=nova.scheduler.weights.all_weighers,nova.scheduler.AntiAffinityWeigher After restarting the scheduler service I get the following error in the nova logs: <178>Aug 1 16:46:11 node-25 nova-nova CRITICAL: Class AntiAffinityWeigher cannot be found (['Traceback (most recent call last):\n', ' File "/usr/lib/python2.6/site-packages/nova/openstack/common/importutils.py", line 31, in import_class\n return getattr(sys.modules[mod_str], class_str)\n', "AttributeError: 'module' object has no attribute 'AntiAffinityWeigher'\n"]) Traceback (most recent call last): File "/usr/bin/nova-scheduler", line 10, in <module> sys.exit(main()) File "/usr/lib/python2.6/site-packages/nova/cmd/scheduler.py", line 39, in main topic=CONF.scheduler_topic) File "/usr/lib/python2.6/site-packages/nova/service.py", line 257, in create db_allowed=db_allowed) File "/usr/lib/python2.6/site-packages/nova/service.py", line 139, in __init__ self.manager = manager_class(host=self.host, *args, **kwargs) File "/usr/lib/python2.6/site-packages/nova/scheduler/manager.py", line 65, in __init__ self.driver = importutils.import_object(scheduler_driver) File "/usr/lib/python2.6/site-packages/nova/openstack/common/importutils.py", line 40, in import_object return import_class(import_str)(*args, **kwargs) File "/usr/lib/python2.6/site-packages/nova/scheduler/filter_scheduler.py", line 59, in __init__ super(FilterScheduler, self).__init__(*args, **kwargs) File "/usr/lib/python2.6/site-packages/nova/scheduler/driver.py", line 103, in __init__ CONF.scheduler_host_manager) File "/usr/lib/python2.6/site-packages/nova/openstack/common/importutils.py", line 40, in import_object return import_class(import_str)(*args, **kwargs) File "/usr/lib/python2.6/site-packages/nova/scheduler/host_manager.py", line 297, in __init__ CONF.scheduler_weight_classes) File "/usr/lib/python2.6/site-packages/nova/loadables.py", line 105, in get_matching_classes obj = importutils.import_class(cls_name) File "/usr/lib/python2.6/site-packages/nova/openstack/common/importutils.py", line 35, in import_class traceback.format_exception(*sys.exc_info()))) ImportError: Class AntiAffinityWeigher cannot be found (['Traceback (most recent call last):\n', ' File "/usr/lib/python2.6/site-packages/nova/openstack/common/importutils.py", line 31, in import_class\n return getattr(sys.modules[mod_str], class_str)\n', "AttributeError: 'module' object has no attribute 'AntiAffinityWeigher'\n"]) I have also tried a few different naming conventions such as "AntiAffinityWeigher.AntiAffinityWeigher" and "myWeigher.AntiAffinityWeigher" to no avail. Any help would be greatly appreciated. Thanks, Danny
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