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# -*- coding: utf-8 -*-
#
# Copyright (C) 2016 Red Hat, Inc.
#
# 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 six
from tooz import hashring
class Partitioner(object):
"""Partition set of objects across several members.
Objects to be partitioned should implement the __tooz_hash__ method to
identify themselves across the consistent hashring. This should method
return bytes.
"""
DEFAULT_PARTITION_NUMBER = hashring.HashRing.DEFAULT_PARTITION_NUMBER
def __init__(self, coordinator, group_id,
partitions=DEFAULT_PARTITION_NUMBER):
members = coordinator.get_members(group_id)
self.partitions = partitions
self.group_id = group_id
self._coord = coordinator
caps = [(m, self._coord.get_member_capabilities(self.group_id, m))
for m in members.get()]
self._coord.watch_join_group(self.group_id, self._on_member_join)
self._coord.watch_leave_group(self.group_id, self._on_member_leave)
self.ring = hashring.HashRing([], partitions=self.partitions)
for m_id, cap in caps:
self.ring.add_node(m_id, cap.get().get("weight", 1))
def _on_member_join(self, event):
weight = self._coord.get_member_capabilities(
self.group_id, event.member_id).get().get("weight", 1)
self.ring.add_node(event.member_id, weight)
def _on_member_leave(self, event):
self.ring.remove_node(event.member_id)
@staticmethod
def _hash_object(obj):
if hasattr(obj, "__tooz_hash__"):
return obj.__tooz_hash__()
return six.text_type(obj).encode('utf8')
def members_for_object(self, obj, ignore_members=None, replicas=1):
"""Return the members responsible for an object.
:param obj: The object to check owning for.
:param member_id: The member to check if it owns the object.
:param ignore_members: Group members to ignore.
:param replicas: Number of replicas for the object.
"""
return self.ring.get_nodes(self._hash_object(obj),
ignore_nodes=ignore_members,
replicas=replicas)
def belongs_to_member(self, obj, member_id,
ignore_members=None, replicas=1):
"""Return whether an object belongs to a member.
:param obj: The object to check owning for.
:param member_id: The member to check if it owns the object.
:param ignore_members: Group members to ignore.
:param replicas: Number of replicas for the object.
"""
return member_id in self.members_for_object(
obj, ignore_members=ignore_members, replicas=replicas)
def belongs_to_self(self, obj, ignore_members=None, replicas=1):
"""Return whether an object belongs to this coordinator.
:param obj: The object to check owning for.
:param ignore_members: Group members to ignore.
:param replicas: Number of replicas for the object.
"""
return self.belongs_to_member(obj, self._coord._member_id,
ignore_members=ignore_members,
replicas=replicas)
def stop(self):
"""Stop the partitioner."""
self._coord.unwatch_join_group(self.group_id, self._on_member_join)
self._coord.unwatch_leave_group(self.group_id, self._on_member_leave)
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