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# 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__)
class HashRingManager(object):
_hash_rings = (None, 0)
_lock = threading.Lock()
def __init__(self, use_groups=True, cache=True):
self.dbapi = dbapi.get_instance()
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, updated_at = self.__class__._hash_rings
if hash_rings is not None and updated_at >= limit:
return hash_rings
with self._lock:
hash_rings, updated_at = self.__class__._hash_rings
if hash_rings is None or updated_at < limit:
LOG.debug('Rebuilding cached hash rings')
hash_rings = self._load_hash_rings()
self.__class__._hash_rings = hash_rings, time.time()
LOG.debug('Finished rebuilding hash rings, available drivers '
'are %s', ', '.join(hash_rings))
return 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
@classmethod
def reset(cls):
with cls._lock:
LOG.debug('Resetting cached hash rings')
cls._hash_rings = (None, 0)
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
ring = self.ring # a property, don't load twice
if not ring:
raise exception.TemporaryFailure()
try:
if self.use_groups:
return ring['%s:%s' % (conductor_group, driver_name)]
return ring[driver_name]
except KeyError:
raise exception.DriverNotFound(
_("The driver '%s' is unknown.") % driver_name)
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