Redis如何实现数据分片扩展功能

hash_slot_cnt = 16384  # hash槽数量

def get_slot(s):
    return crc16(s) % hash_slot_cnt  # 根据字符串s计算其hash槽

class RedisCluster:
    def __init__(self, nodes):
        self.nodes = nodes  # 节点列表
        self.slot2node = {}

        for node in self.nodes:
            for slot in node['slots']:
                self.slot2node[slot] = node

    def get_node(self, key):
        slot = get_slot(key)
        return self.slot2node[slot]  # 根据key获取节点

virtual_node_num = 10  # 每个实际节点添加10个虚拟节点

class RedisCluster:
    def __init__(self, nodes):
        self.nodes = nodes
        self.slot2node = {}

        for node in self.nodes:
            for i in range(virtual_node_num):
                virtual_slot = crc16(node['host'] + str(i)) % hash_slot_cnt
                self.slot2node[virtual_slot] = node

    def get_node(self, key):
        slot = get_slot(key)
        return self.slot2node[slot]

def migrate_slot(from_node, to_node, slot):
    if from_node == to_node:  # 节点相同，不需要进行迁移
        return

    data = from_node['client'].cluster('geTKEysinslot', slot, 10)
    print('migrate %d keys to node %s' % (len(data), to_node['host']))

    if data:
        to_node['client'].migrate(to_node['host'], hash_slot_cnt, '', 0, 1000, keys=data)

import redis

hash_slot_cnt = 16384  # hash槽数量
virtual_node_num = 10  # 每个实际节点添加10个虚拟节点

def get_slot(s):
    return crc16(s) % hash_slot_cnt

def migrate_slot(from_node, to_node, slot):
    if from_node == to_node:
        return

    data = from_node['client'].cluster('getkeysinslot', slot, 10)
    print('migrate %d keys to node %s' % (len(data), to_node['host']))

    if data:
        to_node['client'].migrate(to_node['host'], hash_slot_cnt, '', 0, 1000, keys=data)

class RedisCluster:
    def __init__(self, nodes):
        self.nodes = nodes
        self.slot2node = {}

        for node in self.nodes:
            for i in range(virtual_node_num):
                virtual_slot = crc16(node['host'] + str(i)) % hash_slot_cnt
                self.slot2node[virtual_slot] = node

    def get_node(self, key):
        slot = get_slot(key)
        return self.slot2node[slot]

    def add_node(self, node):
        self.nodes.append(node)

        for i in range(virtual_node_num):
            virtual_slot = crc16(node['host'] + str(i)) % hash_slot_cnt
            self.slot2node[virtual_slot] = node

        for slot in range(hash_slot_cnt):
            if self.slot2node[slot]['host'] == node['host']:
                migrate_slot(self.slot2node[slot], node, slot)

    def remove_node(self, node):
        self.nodes.remove(node)

        for i in range(virtual_node_num):
            virtual_slot = crc16(node['host'] + str(i)) % hash_slot_cnt
            del self.slot2node[virtual_slot]

        for slot in range(hash_slot_cnt):
            if self.slot2node[slot]['host'] == node['host']:
                new_node = None

                for i in range(len(self.nodes)):
                    if self.nodes[i]['host'] != node['host'] and self.nodes[i]['slots']:
                        new_node = self.nodes[i]
                        break

                if new_node:
                    migrate_slot(node, new_node, slot)
                else:
                    print('no new node for slot %d' % slot)

if __name__ == '__main__':
    nodes = [
        {'host': '127.0.0.1', 'port': 7000, 'slots': [0, 1, 2]},
        {'host': '127.0.0.1', 'port': 7001, 'slots': [3, 4, 5]},
        {'host': '127.0.0.1', 'port': 7002, 'slots': [6, 7, 8]},
        {'host': '127.0.0.1', 'port': 7003, 'slots': []},
        {'host': '127.0.0.1', 'port': 7004, 'slots': []},
        {'host': '127.0.0.1', 'port': 7005, 'slots': []},
        {'host': '127.0.0.1', 'port': 7006, 'slots': []},
        {'host': '127.0.0.1', 'port': 7007, 'slots': []},
        {'host': '127.0.0.1', 'port': 7008, 'slots': []},
        {'host': '127.0.0.1', 'port': 7009, 'slots': []},
    ]

    clients = []
    for node in nodes:
        client = redis.Redis(host=node['host'], port=node['port'])
        node['client'] = client
        clients.append(client)

    cluster = RedisCluster(nodes)

    for key in range(100):
        node = cluster.get_node(str(key))
        node['client'].set('key_%d' % key, key)

    cluster.add_node({'host': '127.0.0.1', 'port': 7010, 'slots': []})

    for key in range(100, 200):
        node = cluster.get_node(str(key))
        node['client'].set('key_%d' % key, key)

    cluster.remove_node(nodes[-1])