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Danny-

People have been thinking about affinity/anti-affinity scheduling so this is a good area to look at but we might want to think of a general approach that addresses this and other issues.  I know that Yathi & Debo have proposed a BP:

                https://blueprints.launchpad.net/nova/+spec/solver-scheduler

you might want to check it out and see how it relates to your issues.

--
Don Dugger
"Censeo Toto nos in Kansa esse decisse." - D. Gale
Ph: 303/443-3786

From: Danny Beutler [mailto:dannybeutler at gmail.com]
Sent: Friday, August 1, 2014 10:47 AM
To: openstack at lists.openstack.org
Subject: [Openstack] Custom Nova Scheduler Weigher

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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