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参考教程：2小时吃透4种分布式限流算法

1.计数器限流

public class CounterLimiter {// 开始时间private static long startTime = System.currentTimeMillis();// 时间间隔，单位为msprivate long interval = 1000L;// 限制访问次数private int limitCount = 2;// 访问次数private int reqCount = 0;private synchronized boolean tryAcquire(){long nowTime = System.currentTimeMillis();if(nowTime < startTime + interval){if(reqCount + 1 > limitCount){System.out.println(Thread.currentThread().getName() + "被限流了");return true;}reqCount++;System.out.println(Thread.currentThread().getName() + "通过了");return false;}else {reqCount = 1;startTime = nowTime;System.out.println(Thread.currentThread().getName() + "通过了");return false;}}public static void main(String[] args) {CounterLimiter counterLimiter = new CounterLimiter();for (int i = 0; i < 10; i++) {new Thread(() ->{counterLimiter.tryAcquire();}).start();}}}

2.滑动时间窗口限流

import java.util.LinkedList;public class SlidingTimeWindowLimiter {// 请求数量private int reqCount;// 窗口集合private LinkedList<Integer> slots = new LinkedList<>();// 限制访问量private int limitNum = 2;// 窗口数量private int windowNum = 100;// 每个窗口的时间范围，单位msprivate long windowLength = 100L;public synchronized Boolean limit(){if(reqCount + 1 > limitNum){System.out.println(Thread.currentThread().getName() + ": 被拦截了");return true;}reqCount++;slots.set(slots.size() - 1, slots.peekLast() + 1);System.out.println(Thread.currentThread().getName() + ": 通过了");return false;}public SlidingTimeWindowLimiter(){slots.addLast(0);new Thread(() -> {while (true){try {Thread.sleep(windowLength);}catch (InterruptedException e){e.printStackTrace();}slots.addLast(0);if(slots.size() > windowNum){reqCount = reqCount - slots.peekLast();slots.removeLast();System.out.println("滑动格子：" + reqCount);}}}).start();}public static void main(String[] args) {SlidingTimeWindowLimiter slidingTimeWindowLimiter = new SlidingTimeWindowLimiter();for (int i = 0; i < 10; i++) {new Thread(() -> {slidingTimeWindowLimiter.limit();}).start();}}}

3.漏桶算法

public class LeakyBucketLimiter {// 初始时间private long timestamp = System.currentTimeMillis();// 漏桶容量private long capacity = 5;// 流出速率private long rate = 10;// 桶内有多少请求private long water = 0;public synchronized Boolean limit(){long now = System.currentTimeMillis();water = Math.max(0, water - (now - timestamp) / 1000 * rate);timestamp = now;if((water + 1) <= capacity){water++;System.out.println(Thread.currentThread().getName() + "通过了");return false;}else{System.out.println(Thread.currentThread().getName() + "被拦截了");return true;}}public static void main(String[] args) {LeakyBucketLimiter counterLimiter = new LeakyBucketLimiter();for (int i = 0; i < 10; i++) {new Thread(() ->{counterLimiter.limit();}).start();}}}

4.令牌桶算法

public class TokenBucketLimiter {// 初始时间private long timeStamp = System.currentTimeMillis();// 令牌桶容量private long capacity = 5;// 每秒生成令牌的数量private long rate  = 2;// 桶内的令牌数private long tokens = 0;public synchronized Boolean limit(){long now = System.currentTimeMillis();tokens = Math.min(capacity, tokens + (now - timeStamp) * rate);timeStamp = now;// 没有令牌了if(tokens < 1){System.out.println(Thread.currentThread().getName() + "被拦截了");return true;}else {tokens--;System.out.println(Thread.currentThread().getName() + "通过了");return false;}}public static void main(String[] args) {TokenBucketLimiter slidingTimeWindowLimiter = new TokenBucketLimiter();for (int i = 0; i < 10; i++) {new Thread(() -> {slidingTimeWindowLimiter.limit();}).start();}}
}