令牌桶算法实现API限流

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令牌桶算法( Token Bucket )和 Leaky Bucket 效果一样但方向相反的算法,更加容易理解.随着时间流逝,系统会按恒定 1/QPS 时间间隔(如果 QPS=100 ,则间隔是 10ms )往桶里加入 Token(想象和漏洞漏水相反,有个水龙头在不断的加水),如果桶已经满了就不再加了.新请求来临时,会各自拿走一个 Token ,如果没有 Token 可拿了就阻塞或者拒绝服务.

@Autowired
private JedisClientService jedisClient; public boolean acquire(String key, Integer permits, long currMillSecond) {
try { //针对新用户创建令牌桶
if (!jedisClient.exists(key)) {
jedisClient.hset(key, "last_mill_second", String.valueOf(currMillSecond));
jedisClient.hset(key, "curr_permits", "0");
jedisClient.hset(key, "max_permits", "50");
jedisClient.hset(key, "rate", "400");
return true;
}
//获取令牌桶信息，上一个令牌时间，当前可用令牌数，最大令牌数，令牌消耗速率
List<String> limitInfo = jedisClient.hmget(key, "last_mill_second", "curr_permits", "max_permits", "rate");
long lastMillSecond = Long.parseLong(limitInfo.get(0));
Integer currPermits = Integer.valueOf(limitInfo.get(1));
Integer maxPermits = Integer.valueOf(limitInfo.get(2));
Double rate = Double.valueOf(limitInfo.get(3));
//向桶里面添加令牌
Double reversePermitsDouble = ((currMillSecond - lastMillSecond) / 1000) * rate; Integer reversePermits = reversePermitsDouble.intValue();
Integer expectCurrPermits = reversePermits + currPermits;
Integer localCurrPermits = Math.min(expectCurrPermits, maxPermits);
//添加令牌之后更新时间
if (reversePermits > 0) {
jedisClient.hset(key, "last_mill_second", String.valueOf(currMillSecond));
}
//判断桶里面剩余的令牌数目
if (localCurrPermits - permits >= 0) {
jedisClient.hset(key, "curr_permits", String.valueOf(localCurrPermits - permits));
return true;
} else {
jedisClient.hset(key, "curr_permits", String.valueOf(localCurrPermits));
return false;
}
} catch (Exception e) {
e.printStackTrace();
return false;
}
}