guava 限流RateLimiter 初探（一）

Guava RateLimiter

Guava RateLimiter原理

Guava RateLimiter基于令牌桶算法，我们只需要告诉RateLimiter系统限制的QPS是多少，那么RateLimiter将以这个速度往桶里面放入令牌，然后请求的时候，通过tryAcquire()方法向RateLimiter获取许可（令牌）。

API说明

// 每过permitsPerSecond秒钟创建一个令牌
public static RateLimiter create(double permitsPerSecond) {
        return create(permitsPerSecond, RateLimiter.SleepingStopwatch.createFromSystemTimer());
    }

//  获取permits个许可花费的时间
public double acquire(int permits) {
        long microsToWait = this.reserve(permits);
        this.stopwatch.sleepMicrosUninterruptibly(microsToWait);
        return 1.0D * (double)microsToWait / (double)TimeUnit.SECONDS.toMicros(1L);
}

//  尝试能否在timeout时间内获取permits个许可，获取成功返回true，否则false
public boolean tryAcquire(int permits, long timeout, TimeUnit unit) {
    ... ...
}

demo

• acquire

import com.google.common.util.concurrent.RateLimiter;

public class RateLimterTest {
    
    private RateLimiter rateLimiter = RateLimiter.create(1);

    public static void main(String[] args) {
        RateLimterTest rateLimterTest = new RateLimterTest();
        for (int i = 0; i < 1000; i++) {
            double waitTime = rateLimterTest.rateLimiter.acquire();
            System.out.println("waitTime：" + waitTime);
        }
    }
}

<====
waitTime：0.0
waitTime：0.99648
waitTime：0.99457
waitTime：0.997249
waitTime：0.997921
waitTime：0.998888

• tryAcquire

import com.google.common.util.concurrent.RateLimiter;

import java.util.concurrent.TimeUnit;

public class RateLimterTest {

    private RateLimiter rateLimiter = RateLimiter.create(1);

    public static void main(String[] args) {
        RateLimterTest rateLimterTest = new RateLimterTest();
        while(true) {
            if (rateLimterTest.rateLimiter.tryAcquire(1, 1/2, TimeUnit.SECONDS)) {
                System.out.println("到你了");
            } else {
                System.out.println("还没到你");
            }
        }
    }
}

参考

【1】超详细的Guava RateLimiter限流原理解析：https://zhuanlan.zhihu.com/p/60979444
【2】guava的限流工具RateLimiter使用
【3】guava maven：https://mvnrepository.com/artifact/com.google.guava/guava
【4】高并发之限流RateLimiter（二）
【5】限流工具RateLimiter：https://blog.csdn.net/weixin_38336658/article/details/83819691