【第五周】课后作业

# coding by python3
class HashRing(object):
    def __init__(self, nodes=None, replicas=1):
        """hash环
        """
        self.replicas = replicas
        self.ring = dict()
        self._sorted_keys = []
        if nodes:
            for node in nodes:
                self.add_node(node)
    def add_node(self, node):
        """加节点入环
        """
        for i in range(0, self.replicas):
            key = self.get_key('%s:%s' % (node, i))
            self.ring[key] = node
            self._sorted_keys.append(key)
        self._sorted_keys.sort()
    def remove_node(self, node):
        """移除节点
        """
        for i in range(0, self.replicas):
            key = self.get_key('%s:%s' % (node, i))
            if key in self.ring:
                del self.ring[key]
                self._sorted_keys.remove(key)
    def get_node(self, string_key):
        """根据key获取节点
        """
        return self.get_node_pos(string_key)[0]
    def get_node_pos(self, string_key):
        """获取节点位置
        """
        if not self.ring:
            return None, None
        key = self.get_key(string_key)
        nodes = self._sorted_keys
        for i in range(0, len(nodes)):
            node = nodes[i]
            if key <= node:
                return self.ring[node], i
        return self.ring[nodes[0]], 0
    def get_key(self, key):
        from hashlib import md5
        key = key.encode(encoding='utf-8')
        m = md5()
        m.update(key)
        return m.hexdigest()