C# redis集群批量操作之slot计算出16384个字符串

引入一个大家都用的到的需求来说吧。

需求：要在三主三从的redis集群，存入数据，会对数据进行批量删除操作，数据要求要在redis集群负载均衡。

思路：

1.存入数据好办

var connect = ConnectionMultiplexer.Connect(redisConn);
var redisDb = connect.GetDatabase();
var res1 = redisDb.StringSet("1", DateTime.Now.ToString(), TimeSpan.FromSeconds(600));
var res2 = redisDb.StringSet("1111", DateTime.Now.ToString(), TimeSpan.FromSeconds(600));

2.批量删除直接异常

redisDb.KeyDelete(new RedisKey[] { "1", "1111" });

Ex:"Multi-key operations must involve a single slot; keys can use 'hash tags' to help this, i.e. '{/users/12345}/account' and '{/users/12345}/contacts' will always be in the same slot"

 

3.查到异常是因为redis hash slot 机制导致的，什么是 hash slot？
hash slot 介绍：https://redis.io/topics/cluster-tutorial

4.加上hash slot 字符串，让key进入同一个slot
var res1 = redisDb.StringSet("{myslot}key1", DateTime.Now.ToString(), TimeSpan.FromSeconds(600));
var res2 = redisDb.StringSet("{myslot}key2", DateTime.Now.ToString(), TimeSpan.FromSeconds(600));
redisDb.KeyDelete(new RedisKey[] { "{myslot}key1", "{myslot}key2" });
能进行批量操作，但是都被分配到了同一台服务器上的同一个槽点，不负载均衡。

5.如何负载均衡， 让Key分布到各个服务器，并且可以批量操作？
如果知道每个槽点对应的字符串，key可以按照算法计算出自己对应的字符串，加上后，就可以进行分组批量增删改操作。

6.hash slot 计算方法
HASH_SLOT = CRC16(key) mod 16384 （crc16-XMODEM）
介绍 ：https://redis.io/topics/cluster-spec

7.net core 计算出16384个slot 字符串 算法例子和 结果模板

        static void Main(string[] args)
        {
            var data = new Dictionary<int, string>();
            var i = 0;
            while (data.Keys.Count < 16384)
            {
                var temp = i.ToString("X");
                var value = Crc16(Encoding.UTF8.GetBytes(temp)) % 16384;
                data[int.Parse(value.ToString())] = temp;
                i++;

            }
            var sb = new StringBuilder();
            foreach (var item in data.OrderBy(s => s.Key))
            {
                var temp = $"slot num:{item.Key}   str:{item.Value} \r\n";
                Console.WriteLine(temp);
                sb.Append(temp);
            }
            File.WriteAllText("data.txt", sb.ToString());
            Console.ReadLine();
        }
        private static ushort Crc16(byte[] bytes)
        {
            ushort poly = 0x1021;
            ushort[] table = new ushort[256];
            ushort initialValue = 0x0;
            ushort temp, a;
            ushort crc = initialValue;
            for (int i = 0; i < table.Length; ++i)
            {
                temp = 0;
                a = (ushort)(i << 8);
                for (int j = 0; j < 8; ++j)
                {
                    if (((temp ^ a) & 0x8000) != 0)
                        temp = (ushort)((temp << 1) ^ poly);
                    else
                        temp <<= 1;
                    a <<= 1;
                }
                table[i] = temp;
            }
            for (int i = 0; i < bytes.Length; ++i)
            {
                crc = (ushort)((crc << 8) ^ table[((crc >> 8) ^ (0xff & bytes[i]))]);
            }
            return crc;
        }

　　data.txt 文件下载

8.校验算出来的字符串 对应 的slot位置 是否正确

 

9.批量设置和批量删除方法
假定三主三从，那么三台服务器，取九个slot字符串，这九个是均分的位置(均分利于集群扩展)。即16384/10=1638 1638是第一位，1638*2是第二位，以此类推取字符串
共九个["1A73F","18B13","1AAD3","184FF","143BF","18413","17B8D","18BFF","1B1C4"]
先分组，再批量插入，再批量删除

try
            {
                var redisConn = "{集群地址}";
                var connect = ConnectionMultiplexer.Connect(redisConn);
                var redisDb = connect.GetDatabase();
                var res1 = redisDb.StringSet("1", DateTime.Now.ToString(), TimeSpan.FromSeconds(600));
                var res2 = redisDb.StringSet("1111", DateTime.Now.ToString(), TimeSpan.FromSeconds(600));
                redisDb.KeyDelete(new RedisKey[] { "1", "1111" });


                var redisSlotKeyList = new string[] { "1A73F", "18B13", "1AAD3", "184FF", "143BF", "18413", "17B8D", "18BFF", "1B1C4" };
                var userIdArray = new int[] { 1, 2, 3, 4, 5, 6, 7, 8, 9, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 };
                //group
                var dic = new Dictionary<int, Dictionary<RedisKey,RedisValue>>();
                foreach (var userId in userIdArray)
                {
                    var index = userId % redisSlotKeyList.Length;
                    var slotKey = redisSlotKeyList[index];
                    var redisKey = $"{{{slotKey}}}test_{userId}";
                    Console.WriteLine($"{ redisKey}  {userId}");
                    if (dic.ContainsKey(index))
                    {
                        dic[index].Add(redisKey, DateTime.Now.ToLongTimeString());
                    }
                    else 
                    {
                        dic[index] = new Dictionary<RedisKey, RedisValue> { { new RedisKey(redisKey), new RedisValue("values") } };
                    }
                }

                //set
                foreach (var item in dic)
                {
                    var addRes = redisDb.StringSet(item.Value.ToArray());
                    Console.WriteLine(addRes);
                }


                //delete
                foreach (var item in dic)
                {
                    var deleteRes = redisDb.KeyDelete(item.Value.Keys.ToArray());
                    Console.WriteLine(deleteRes);
                }



            }
            catch (Exception ex)
            {
                throw ex;
            }

 

10.注意点
集群的分割slot配置不一定的均分的，提前先查看，命令：cluster nodes。 查看之后再根据实际情况取slot string