public class WarmUpController implements TrafficShapingController {
	// FlowRule中設置的閾值
    protected double count;
    // 冷卻因子，默認為3，通過SentinelConfig加載，可以修改
    private int coldFactor;
    // 預警token數(shù)量
    protected int warningToken = 0;
    // 最大token數(shù)量
    private int maxToken;
    // 斜率，用于計算當前生成token的時間間隔，即生成速率
    protected double slope;
	// 令牌桶中剩余令牌數(shù)
    protected AtomicLong storedTokens = new AtomicLong(0);
    // 最后一次添加令牌的時間戳
    protected AtomicLong lastFilledTime = new AtomicLong(0);
    public WarmUpController(double count, int warmUpPeriodInSec, int coldFactor) {
        construct(count, warmUpPeriodInSec, coldFactor);
    }
    public WarmUpController(double count, int warmUpPeriodInSec) {
        construct(count, warmUpPeriodInSec, 3);
    }
    private void construct(double count, int warmUpPeriodInSec, int coldFactor) {
        if (coldFactor <= 1) {
            throw new IllegalArgumentException("Cold factor should be larger than 1");
        }
        this.count = count;
		// 默認為3
        this.coldFactor = coldFactor;
        // thresholdPermits = 0.5 * warmupPeriod / stableInterval.
        // warningToken = 100;
        // 計算預警token數(shù)量
        // 例如 count=5，warmUpPeriodInSec=10，coldFactor=3，則waringToken=5*10/2=25
        warningToken = (int)(warmUpPeriodInSec * count) / (coldFactor - 1);
        // / maxPermits = thresholdPermits + 2 * warmupPeriod / (stableInterval + coldInterval)
        // maxToken = 200
        // 最大token數(shù)量=25+2*10*5/4=50
        maxToken = warningToken + (int)(2 * warmUpPeriodInSec * count / (1.0 + coldFactor));
        // slope
        // slope = (coldIntervalMicros - stableIntervalMicros) / (maxPermits- thresholdPermits);
        // 傾斜度=(3-1)/5/(50-25) = 0.016
        slope = (coldFactor - 1.0) / count / (maxToken - warningToken);
    }
}

stableInterval=1/count=200ms，coldInterval=coldFactor*stableInterval=600ms
warningToken=warmUpPeriodSec/(coldFactor-1)/stableInterval=(warmUpPeriodSec*count)/(coldFactor-1)=25
maxToken=2warmUpPeriodSec/(stableInterval+coldInterval)+warningToken=warningToken+2warmUpPeriodSeccount/(coldFactor+1)=50
slope=(coldInterval-stableInterval)/(maxToken-warningToken)=(coldFactor-1)/count/(maxToken-warningToken)=0.016

public boolean canPass(Node node, int acquireCount, boolean prioritized) {
    // 獲取當前1s的QPS
    long passQps = (long) node.passQps();
    // 獲取上一窗口通過的qps
    long previousQps = (long) node.previousPassQps();
    // 生成和滑落token
    syncToken(previousQps);
    // 如果進入了警戒線，開始調(diào)整他的qps
    long restToken = storedTokens.get();
    // 如果令牌桶中的token數(shù)量大于警戒值，說明還未預熱結束，需要判斷token的生成速度和消費速度
    if (restToken >= warningToken) {
        long aboveToken = restToken - warningToken;
        // 消耗的速度要比warning快，但是要比慢
        // y軸，當前token生成時間 current interval = restToken*slope+stableInterval
        // 計算此時1s內(nèi)能夠生成token的數(shù)量
        double warningQps = Math.nextUp(1.0 / (aboveToken * slope + 1.0 / count));
        // 判斷token消費速度是否小于生成速度，如果是則正常請求，否則限流
        if (passQps + acquireCount <= warningQps) {
            return true;
        }
    } else {
        // 預熱結束，直接判斷是否超過設置的閾值
        if (passQps + acquireCount <= count) {
            return true;
        }
    }

    return false;
}

protected void syncToken(long passQps) {
    long currentTime = TimeUtil.currentTimeMillis();
    // 獲取整秒數(shù)
    currentTime = currentTime - currentTime % 1000;
    // 上一次的操作時間
    long oldLastFillTime = lastFilledTime.get();
    // 判斷成立，如果小于，說明可能出現(xiàn)了時鐘回撥
    // 如果等于，說明當前請求都處于同一秒內(nèi)，則不進行token添加和滑落操作，避免的重復扣減
    // 時間窗口的跨度為1s
    if (currentTime <= oldLastFillTime) {
        return;
    }
    // token數(shù)量
    long oldValue = storedTokens.get();
    long newValue = coolDownTokens(currentTime, passQps);
    // 重置token數(shù)量
    if (storedTokens.compareAndSet(oldValue, newValue)) {
        // token滑落，即token消費
        // 減去上一個時間窗口的通過請求數(shù)
        long currentValue = storedTokens.addAndGet(0 - passQps);
        if (currentValue < 0) {
            storedTokens.set(0L);
        }
        // 設置最后添加令牌時間
        lastFilledTime.set(currentTime);
    }

}
private long coolDownTokens(long currentTime, long passQps) {
    long oldValue = storedTokens.get();
    long newValue = oldValue;

    // 添加令牌的判斷前提條件:
    // 當令牌的消耗程度遠遠低于警戒線的時候
    if (oldValue < warningToken) {
        // 計算過去一段時間內(nèi)，可以通過的QPS總量
        // 初始加載時，令牌數(shù)量達到maxToken
        newValue = (long)(oldValue + (currentTime - lastFilledTime.get()) * count / 1000);
    } else if (oldValue > warningToken) {
        // 處于預熱過程，且消費速度低于冷卻速度，則補充令牌
        if (passQps < (int)count / coldFactor) {
            newValue = (long)(oldValue + (currentTime - lastFilledTime.get()) * count / 1000);
        }
    }
    // 當令牌桶滿了之后，拋棄多余的令牌
    return Math.min(newValue, maxToken);
}