98 lines
3.9 KiB
Python
98 lines
3.9 KiB
Python
# -*- coding: utf-8 -*-
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#
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# Copyright (C) 2016 Red Hat, Inc.
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#
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# Licensed under the Apache License, Version 2.0 (the "License"); you may
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# not use this file except in compliance with the License. You may obtain
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# 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, WITHOUT
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# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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# License for the specific language governing permissions and limitations
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# under the License.
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from tooz import hashring
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class Partitioner(object):
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"""Partition set of objects across several members.
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Objects to be partitioned should implement the __tooz_hash__ method to
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identify themselves across the consistent hashring. This should method
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return bytes.
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"""
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DEFAULT_PARTITION_NUMBER = hashring.HashRing.DEFAULT_PARTITION_NUMBER
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def __init__(self, coordinator, group_id,
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partitions=DEFAULT_PARTITION_NUMBER):
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members = coordinator.get_members(group_id)
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self.partitions = partitions
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self.group_id = group_id
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self._coord = coordinator
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caps = [(m, self._coord.get_member_capabilities(self.group_id, m))
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for m in members.get()]
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self._coord.watch_join_group(self.group_id, self._on_member_join)
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self._coord.watch_leave_group(self.group_id, self._on_member_leave)
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self.ring = hashring.HashRing([], partitions=self.partitions)
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for m_id, cap in caps:
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self.ring.add_node(m_id, cap.get().get("weight", 1))
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def _on_member_join(self, event):
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weight = self._coord.get_member_capabilities(
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self.group_id, event.member_id).get().get("weight", 1)
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self.ring.add_node(event.member_id, weight)
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def _on_member_leave(self, event):
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self.ring.remove_node(event.member_id)
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@staticmethod
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def _hash_object(obj):
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if hasattr(obj, "__tooz_hash__"):
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return obj.__tooz_hash__()
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return str(obj).encode('utf8')
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def members_for_object(self, obj, ignore_members=None, replicas=1):
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"""Return the members responsible for an object.
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:param obj: The object to check owning for.
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:param member_id: The member to check if it owns the object.
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:param ignore_members: Group members to ignore.
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:param replicas: Number of replicas for the object.
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"""
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return self.ring.get_nodes(self._hash_object(obj),
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ignore_nodes=ignore_members,
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replicas=replicas)
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def belongs_to_member(self, obj, member_id,
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ignore_members=None, replicas=1):
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"""Return whether an object belongs to a member.
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:param obj: The object to check owning for.
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:param member_id: The member to check if it owns the object.
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:param ignore_members: Group members to ignore.
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:param replicas: Number of replicas for the object.
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"""
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return member_id in self.members_for_object(
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obj, ignore_members=ignore_members, replicas=replicas)
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def belongs_to_self(self, obj, ignore_members=None, replicas=1):
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"""Return whether an object belongs to this coordinator.
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:param obj: The object to check owning for.
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:param ignore_members: Group members to ignore.
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:param replicas: Number of replicas for the object.
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"""
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return self.belongs_to_member(obj, self._coord._member_id,
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ignore_members=ignore_members,
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replicas=replicas)
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def stop(self):
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"""Stop the partitioner."""
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self._coord.unwatch_join_group(self.group_id, self._on_member_join)
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self._coord.unwatch_leave_group(self.group_id, self._on_member_leave)
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