Source code for ironic.common.hash_ring

# Copyright 2013 Hewlett-Packard Development Company, L.P.
# 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.

import threading
import time

from oslo_log import log
from tooz import hashring

from ironic.common import exception
from ironic.common.i18n import _
from ironic.conf import CONF
from ironic.db import api as dbapi


LOG = log.getLogger(__name__)


[docs]class HashRingManager(object): _hash_rings = None _lock = threading.Lock() def __init__(self, use_groups=True, cache=True): self.dbapi = dbapi.get_instance() self.updated_at = time.time() self.use_groups = use_groups self.cache = cache @property def ring(self): interval = CONF.hash_ring_reset_interval limit = time.time() - interval if not self.cache: return self._load_hash_rings() # Hot path, no lock. Using a local variable to avoid races with code # changing the class variable. hash_rings = self.__class__._hash_rings if hash_rings is not None and self.updated_at >= limit: return hash_rings with self._lock: if self.__class__._hash_rings is None or self.updated_at < limit: LOG.debug('Rebuilding cached hash rings') rings = self._load_hash_rings() self.__class__._hash_rings = rings self.updated_at = time.time() LOG.debug('Finished rebuilding hash rings, available drivers ' 'are %s', ', '.join(rings)) return self.__class__._hash_rings def _load_hash_rings(self): rings = {} d2c = self.dbapi.get_active_hardware_type_dict( use_groups=self.use_groups) for driver_name, hosts in d2c.items(): rings[driver_name] = hashring.HashRing( hosts, partitions=2 ** CONF.hash_partition_exponent, hash_function=CONF.hash_ring_algorithm) return rings
[docs] @classmethod def reset(cls): with cls._lock: LOG.debug('Resetting cached hash rings') cls._hash_rings = None
[docs] def get_ring(self, driver_name, conductor_group): try: return self._get_ring(driver_name, conductor_group) except (exception.DriverNotFound, exception.TemporaryFailure): # NOTE(dtantsur): we assume that this case is more often caused by # conductors coming and leaving, so we try to rebuild the rings. LOG.debug('No conductor from group %(group)s found for driver ' '%(driver)s, trying to rebuild the hash rings', {'driver': driver_name, 'group': conductor_group or '<none>'}) self.__class__.reset() return self._get_ring(driver_name, conductor_group)
def _get_ring(self, driver_name, conductor_group): # There are no conductors, temporary failure - 503 Service Unavailable if not self.ring: raise exception.TemporaryFailure() try: if self.use_groups: return self.ring['%s:%s' % (conductor_group, driver_name)] return self.ring[driver_name] except KeyError: raise exception.DriverNotFound( _("The driver '%s' is unknown.") % driver_name)