# Hash ring

Tooz provides a consistent hash ring implementation. It can be used to map objects (represented via binary keys) to one or several nodes. When the node list changes, the rebalancing of objects across the ring is kept minimal.

    # Copyright (C) 2020 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.

    from tooz import hashring

    hashring = hashring.HashRing({'node1', 'node2', 'node3'})

    # Returns set(['node2'])
    nodes_for_foo = hashring[b'foo']

    # Returns set(['node2', 'node3'])
    nodes_for_foo_with_replicas = hashring.get_nodes(b'foo',
                                                     replicas=2)

    # Returns set(['node1', 'node3'])
    nodes_for_foo_with_replicas = hashring.get_nodes(b'foo',
                                                     replicas=2,
                                                     ignore_nodes={'node2'})

this page last updated: 2022-01-12 20:19:17

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