private int CalculateHashValue(String key)

        {

            int hv;

            switch (_hashingAlgorithm)

            {

                case EnumHashingAlgorithm.Native:

                    hv = key.GetHashCode();

                    break;

                case EnumHashingAlgorithm.OldCompatibleHash:

                    hv = HashingAlgorithmTool.OriginalHashingAlgorithm(key);

                    break;

                case EnumHashingAlgorithm.NewCompatibleHash:

                    hv = HashingAlgorithmTool.NewHashingAlgorithm(key);

                    break;

                default:

                    // use the native hash as a default

                    hv = key.GetHashCode();

                    _hashingAlgorithm = EnumHashingAlgorithm.Native;

                    break;

            }

            return hv;

        }

//哈希取余值，为什么是2的32次方：IPV4的总量是2的32次方个，可以保证环上的IP不重复
long HashValue = (long)Math.Pow(2, 32);
将Key生成一致性哈希环中的哈希值
        private long GenerateConsistentHashValue(String key)
        {
            long serverHV = CalculateHashValue(key);
            long mod = serverHV % HashValue;
            if (mod < 0)
            {
                mod = mod + HashValue;
            }
            return mod;
        }

        private void GenerateServersToBuckets()
        {
            for (int i = 0; i < _servers.Count; i++)
            {
                // 创建物理节点
                String server = _servers[i];
                long mod = GenerateConsistentHashValue(server);
                buckets.Add(mod, server);
                //创建虚拟节点
                List<String> virtualHostServers = GenerateVirtualServer(server, this.Weights[i]);
                foreach (String v in virtualHostServers)
                {
                    mod = GenerateConsistentHashValue(v);
                    buckets.Add(mod, server);
                }
            }
        }

private static List<String> GenerateVirtualServer(String server, int count)
        {
            if (count > 255)
            {
                throw new ArgumentException("每服务器虚拟节点数不能超过254");
            }
            List<String> virtualServers = new List<string>();

            #region 1.按修改IP值+随机GUID生成虚拟节点
            String[] ipaddr = server.Split(':');
            String ip = ipaddr[0];
            string port = ipaddr[1];
            int header = Convert.ToInt32(ip.Split('.')[0]);
            String invariantIPPart = ip.Substring(ip.IndexOf('.'));
            int succ = 0;
            for (int i = 1; i <= 255; i++)
            {
                if (i != header)
                {
                    String virtualServer = i.ToString() + invariantIPPart + ":" + port + i;// Guid.NewGuid().ToString("N").ToUpper();
                    virtualServers.Add(virtualServer);
                    succ++;
                }
                if (succ == count)
                {
                    break;
                }
            } 
            #endregion

            #region 2.物理节点自增序号||随机GUID
            //for (int i = 0; i < count; i++)
            //{
            //    //virtualServers.Add(server + i.ToString());
            //    virtualServers.Add(server + i.ToString()+Guid.NewGuid().ToString());
            //} 
            #endregion

            #region 32.其它生成算法
            //TODO
            #endregion

            return virtualServers;
        }

private String FindServer(String key, ref long startIndex)
        {
            long mod = startIndex;
            if (mod < 0)
            {
                mod = GenerateConsistentHashValue(key);
            }
            foreach (KeyValuePair<long, String> kvp in buckets)
            {
                startIndex = kvp.Key;
                //找到第一个大于或等于key的服务器
                if (kvp.Key >= mod)
                {
                    //若找到的服务器不可用，则继续查找下一服务器
                    if (_hostDead.ContainsKey(kvp.Value))
                    {
                        continue;
                    }
                    return kvp.Value;
                }
            }
            //如果大于mod的服务器均不可用或没有找到，则从头开始找可用服务器
            foreach (KeyValuePair<long, String> kvp in buckets)
            {
                startIndex = kvp.Key;
                if (kvp.Key >= mod)
                {
                    break;
                }
                if (_hostDead.ContainsKey(kvp.Value))
                {
                    continue;
                }
                return kvp.Value;
            }
            //不存在可用服务器
            return string.Empty;
        }

 public ISockIO GetSock(string key)
        {
            if (buckets.Count == 0)
            {
                return null;
            }

            if (buckets.Count == 1)
            {
                return GetConnection(buckets[0]);
            }

            long startIndex = -1;//开始查找位置，-1表示从hash(key)% HashValue位置开始查找
            int tries = 0;//重试次数，不超过总服务器数
            while (tries++ <= this.servers.Count)
            {
                String server = FindServer(key, ref startIndex);
                //找不到可用的服务器
                if (String.IsNullOrEmpty(server))
                {
                    return null;
                }
                ISockIO sock = GetConnection(server);
                if (sock != null)
                {
                    WriteLog.Write("key：" + key + ",server：" + server);
                    return sock;
                }
                //是否需要故障转移，若需要，则会继续查找可用的服务器
                if (!_failover)
                {
                    return null;
                }
            }
            return null;
        }