/usr/lib/python2.7/dist-packages/tooz/hashring.py is in python-tooz 1.59.0-0ubuntu1.
This file is owned by root:root, with mode 0o644.
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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 | # -*- 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 bisect
import hashlib
import six
import tooz
from tooz import utils
class UnknownNode(tooz.ToozError):
"""Node is unknown."""
def __init__(self, node):
super(UnknownNode, self).__init__("Unknown node `%s'" % node)
self.node = node
class HashRing(object):
"""Map objects onto nodes based on their consistent hash."""
DEFAULT_PARTITION_NUMBER = 2**5
def __init__(self, nodes, partitions=DEFAULT_PARTITION_NUMBER):
"""Create a new hashring.
:param nodes: List of nodes where objects will be mapped onto.
:param partitions: Number of partitions to spread objects onto.
"""
self.nodes = {}
self._ring = dict()
self._partitions = []
self._partition_number = partitions
self.add_nodes(set(nodes))
def add_node(self, node, weight=1):
"""Add a node to the hashring.
:param node: Node to add.
:param weight: How many resource instances this node should manage
compared to the other nodes (default 1). Higher weights will be
assigned more resources. Three nodes A, B and C with weights 1, 2 and 3
will each handle 1/6, 1/3 and 1/2 of the resources, respectively.
"""
return self.add_nodes((node,), weight)
def add_nodes(self, nodes, weight=1):
"""Add nodes to the hashring with equal weight
:param nodes: Nodes to add.
:param weight: How many resource instances this node should manage
compared to the other nodes (default 1). Higher weights will be
assigned more resources. Three nodes A, B and C with weights 1, 2 and 3
will each handle 1/6, 1/3 and 1/2 of the resources, respectively.
"""
for node in nodes:
key = utils.to_binary(node, 'utf-8')
key_hash = hashlib.md5(key)
for r in six.moves.range(self._partition_number * weight):
key_hash.update(key)
self._ring[self._hash2int(key_hash)] = node
self.nodes[node] = weight
self._partitions = sorted(self._ring.keys())
def remove_node(self, node):
"""Remove a node from the hashring.
Raises py:exc:`UnknownNode`
:param node: Node to remove.
"""
try:
weight = self.nodes.pop(node)
except KeyError:
raise UnknownNode(node)
key = utils.to_binary(node, 'utf-8')
key_hash = hashlib.md5(key)
for r in six.moves.range(self._partition_number * weight):
key_hash.update(key)
del self._ring[self._hash2int(key_hash)]
self._partitions = sorted(self._ring.keys())
@staticmethod
def _hash2int(key):
return int(key.hexdigest(), 16)
def _get_partition(self, data):
hashed_key = self._hash2int(hashlib.md5(data))
position = bisect.bisect(self._partitions, hashed_key)
return position if position < len(self._partitions) else 0
def _get_node(self, partition):
return self._ring[self._partitions[partition]]
def get_nodes(self, data, ignore_nodes=None, replicas=1):
"""Get the set of nodes which the supplied data map onto.
:param data: A byte identifier to be mapped across the ring.
:param ignore_nodes: Set of nodes to ignore.
:param replicas: Number of replicas to use.
:return: A set of nodes whose length depends on the number of replicas.
"""
partition = self._get_partition(data)
ignore_nodes = set(ignore_nodes) if ignore_nodes else set()
candidates = set(self.nodes.keys()) - ignore_nodes
replicas = min(replicas, len(candidates))
nodes = set()
while len(nodes) < replicas:
node = self._get_node(partition)
if node not in ignore_nodes:
nodes.add(node)
partition = (partition + 1
if partition + 1 < len(self._partitions) else 0)
return nodes
def __getitem__(self, key):
return self.get_nodes(key)
def __len__(self):
return len(self._partitions)
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