132 lines
4.5 KiB
Python
132 lines
4.5 KiB
Python
# Copyright (c) 2015 Mirantis Inc.
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
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# implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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import bisect
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import hashlib
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from oslo_config import cfg
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from oslo_log import log
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from oslo_utils import uuidutils
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from tooz import coordination
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LOG = log.getLogger(__name__)
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coordinator_opts = [
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cfg.IntOpt('coordinator_heartbeat_interval',
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default=1,
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help='Interval size between heartbeat execution in seconds. '
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'Heartbeats are executed to make sure that connection to '
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'the coordination server is active.'),
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cfg.IntOpt('hash_ring_replicas_count',
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default=40,
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help='Number of points that belongs to each member on a hash '
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'ring. The larger number leads to a better distribution.')
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]
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CONF = cfg.CONF
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CONF.register_opts(coordinator_opts)
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class Coordinator(object):
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def __init__(self, backend_url):
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self.coordinator = None
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self.member_id = uuidutils.generate_uuid()
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if backend_url:
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try:
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self.coordinator = coordination.get_coordinator(
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backend_url, self.member_id)
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self.coordinator.start()
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LOG.info('Coordination backend loaded successfully.')
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except coordination.ToozError:
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LOG.error('Error connecting to coordination backend.')
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raise
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def is_started(self):
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if self.coordinator:
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return self.coordinator.is_started
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return False
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def heartbeat(self):
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if self.coordinator:
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self.coordinator.heartbeat()
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def join_group(self, group_id):
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if self.coordinator:
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try:
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self.coordinator.join_group(group_id).get()
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except coordination.GroupNotCreated:
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try:
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self.coordinator.create_group(group_id).get()
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except coordination.GroupAlreadyExist:
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pass
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self.coordinator.join_group(group_id).get()
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def get_members(self, group_id):
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if self.coordinator:
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for i in range(2):
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try:
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members = self.coordinator.get_members(group_id).get()
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if self.member_id in members:
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return members
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self.join_group(group_id)
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except coordination.GroupNotCreated:
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self.join_group(group_id)
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except coordination.ToozError as e:
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LOG.error("Couldn't get members of {group} group. "
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"Reason: {ex}".format(
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group=group_id, ex=str(e)))
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return []
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class HashRing(Coordinator):
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def __init__(self, backend_url, group_id):
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self.group_id = group_id
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self.replicas = CONF.hash_ring_replicas_count
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super(HashRing, self).__init__(backend_url)
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self.join_group(group_id)
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@staticmethod
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def _hash(key):
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return int(
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hashlib.md5(str(key).encode('utf-8')).hexdigest(), 16) # nosec
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def _build_ring(self):
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ring = {}
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members = self.get_members(self.group_id)
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for member in members:
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for r in range(self.replicas):
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hashed_key = self._hash('%s:%s' % (member, r))
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ring[hashed_key] = member
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return ring, sorted(ring.keys())
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def _check_object(self, object, ring, sorted_keys):
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"""Checks if this object belongs to this member or not"""
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hashed_key = self._hash(object.id)
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position = bisect.bisect(sorted_keys, hashed_key)
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position = position if position < len(sorted_keys) else 0
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return ring[sorted_keys[position]] == self.member_id
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def get_subset(self, objects):
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"""Returns subset that belongs to this member"""
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if self.coordinator:
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ring, keys = self._build_ring()
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if ring:
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return [obj for obj in objects if self._check_object(
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obj, ring, keys)]
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return []
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return objects
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