redis eval 实现限流

大致流程:

1. 每次请求就写入有序集合里面，集合的sorce值是当前毫秒时间戳（防止秒出现重复），可以认为每一次请求就一个时间戳在里面。

2. 从集合里面去掉10分钟以前所有的集合数据。然后计算出当前的集合里面数量

3. 根据这个数量来与我们阈值做大小判断，如果超过就锁住，否则继续走下去

//将我们时间戳写入我们redis的有序集合里面
 Redis::zadd('user:1:request:nums',1561456435,'1561456435.122');
//设置key的过期时间为10分钟
Redis::expire('user:1:request:nums',300);
//删除我们10分钟以前的数据
Redis::ZREMRANGEBYSCORE('user:1:request:nums',0,1561456135);
//获取里面剩下请求个数
$request_nums=(int)Redis::zcard(self::TIMELINE_ELEVEL_KEY);
if($request_nums >= 10){
    //加入小黑屋，下次再进来就要锁定判断
}
...

private final static String TEXT="local ratelimit_info = redis.pcall('HMGET',KEYS[1],'last_time','current_token')\n" +
            "local last_time = ratelimit_info[1]\n" +
            "local current_token = tonumber(ratelimit_info[2])\n" +
            "local max_token = tonumber(ARGV[1])\n" +
            "local token_rate = tonumber(ARGV[2])\n" +
            "local current_time = tonumber(ARGV[3])\n" +
            "if current_token == nil then\n" +
            "  current_token = max_token\n" +
            "  last_time = current_time\n" +
            "else\n" +
            "  local past_time = current_time-last_time\n" +
            "  \n" +
            "  if past_time>1000 then\n" +
            "\t  current_token = current_token+token_rate\n" +
            "\t  last_time = current_time\n" +
            "  end\n" +
            "\n" +
            "  if current_token>max_token then\n" +
            "    current_token = max_token\n" +
            "\tlast_time = current_time\n" +
            "  end\n" +
            "end\n" +
            "\n" +
            "local result = 0\n" +
            "if(current_token>0) then\n" +
            "  result = 1\n" +
            "  current_token = current_token-1\n" +
            "  last_time = current_time\n" +
            "end\n" +
            "redis.call('HMSET',KEYS[1],'last_time',last_time,'current_token',current_token)\n" +
            "return result";