Sentinel 限流算法

1、计数器固定窗口算法

计数器固定窗口算法是最简单的限流算法，实现方式也比较简单。就是通过维护一个单位时间内的计数值，每当一个请求通过时，就将计数值加 1，当计数值超过预先设定的阈值时，就拒绝单位时间内的其他请求。如果单位时间已经结束，则将计数器清零，开启下一轮的计数。

package com.on.sentinel;
import com.on.sentinel.exception.BlockException;
import java.util.concurrent.Executors;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicInteger;

public class CounterRateLimit implements RateLimit, Runnable {
    /**
     * 阈值
     */
    private Integer limitCount;

    /**
     * 当前通过请求数
     */
    private AtomicInteger passCount;

    /**
     * 统计时间间隔
     */
    private long period;
    private TimeUnit timeUnit;

    private ScheduledExecutorService scheduledExecutorService;

    public CounterRateLimit(Integer limitCount) {
        this(limitCount, 1000, TimeUnit.MILLISECONDS);
    }

    public CounterRateLimit(Integer limitCount, long period, TimeUnit timeUnit) {
        this.limitCount = limitCount;
        this.period = period;
        this.timeUnit = timeUnit;
        passCount = new ();
        .startResetTask();
    }

    
        BlockException {
         (passCount.incrementAndGet() > limitCount) {
              ();
        }
         ;
    }

    
       {
        scheduledExecutorService = Executors.newSingleThreadScheduledExecutor();
        scheduledExecutorService.scheduleAtFixedRate(, , period, timeUnit);
    }

    
       {
        passCount.set();
    }
}