# -*- coding: utf-8 -*-import hashlibimport mathclass YiZhiHash(object): def __init__(self, nodes=None, n_number=3): """ :param nodes: 所有的节点 :param n_number: 一个节点对应多少个虚拟节点 :return: """ self._n_number = n_number #每一个节点对应多少个虚拟节点，这里默认是3个 self._node_dict = dict() #用于将虚拟节点的hash值与node的对应关系 self._sort_list = [] #用于存放所有的虚拟节点的hash值，这里需要保持排序 self._access_times = {} if nodes: for node in nodes: self.add_node(node) def add_node(self, node): """ 添加node，首先要根据虚拟节点的数目，创建所有的虚拟节点，并将其与对应的node对应起来 当然还需要将虚拟节点的hash值放到排序的里面 这里在添加了节点之后，需要保持虚拟节点hash值的顺序 :param node: :return: """ for i in range(self._n_number): node_str = "%s_%s" % (node, i) key = self._gen_key(node_str) self._node_dict[key] = node self._sort_list.append(key) self._sort_list.sort() def remove_node(self, node): """ 这里一个节点的退出，需要将这个节点的所有的虚拟节点都删除 :param node: :return: """ for i in range(self._n_number): node_str = "%s_%s" % (node, i) key = self._gen_key(node_str) del self._node_dict[key] self._sort_list.remove(key) def get_node(self, key_str): """ 返回这个字符串应该对应的node，这里先求出字符串的hash值，然后找到第一个小于等于的虚拟节点，然后返回node 如果hash值大于所有的节点，那么用第一个虚拟节点 :param : :return: """ if self._sort_list: key = self._gen_key(key_str) for node_key in self._sort_list: if key <= node_key: access_key = self._node_dict[node_key] access_val = self._access_times.get(access_key, 0) access_val += 1 self._access_times[access_key] = access_val return self._node_dict[node_key] return self._node_dict[self._sort_list[0]] else: return None def print(self): print("show the server with hash") for k, v in self._access_times.items(): print("The node {} access hit times: {}".format(k, v)) def get_access_deviation(self): access_times_avg = 0 access_times_sum = 0 access_times_deviation = None len_access_times = len(self._access_times) for k, v in self._access_times.items(): access_times_sum += v access_times_avg = access_times_sum / len_access_times total_square_substraction = 0 for k, v in self._access_times.items(): total_square_substraction += (v - access_times_avg)**2 access_times_deviation = math.sqrt(total_square_substraction/len_access_times) return access_times_deviation @staticmethod def _gen_key(key_str): """ 通过key，返回当前key的hash值，这里采用md5 :param key: :return: """ md5_str = hashlib.md5(key_str.encode('utf-8')).hexdigest() return int(md5_str, 16)yzhash = YiZhiHash(["192.168.1.1", "192.168.1.2", "192.168.1.3", "192.168.1.4", "192.168.1.5", "192.168.1.6", "192.168.1.7", "192.168.1.8", "192.168.1.9", "192.168.1.10" ])if __name__ == "__main__": SERVER_NODES = [ "192.168.1.1", "192.168.1.2", "192.168.1.3", "192.168.1.4", "192.168.1.5", "192.168.1.6", "192.168.1.7", "192.168.1.8", "192.168.1.9", "192.168.1.10" ] server_nodes_with_hash = YiZhiHash(SERVER_NODES, n_number=100) for k in range(1000000): print("Access {} from node {}".format(k, server_nodes_with_hash.get_node(str(k)))) print("access deviation is {}".format(server_nodes_with_hash.get_access_deviation()))
