流量控制和流量整形

流量控制和流量整形

令牌桶算法

漏桶算法

Java实现

Guava的com.google.common.util.concurrent.RateLimiter来实现基于令牌桶的流控。RateLimiter令牌桶算法的单桶实现。

public class TrafficShaper {

    public static class RateLimitException extends Exception {

        private static final long serialVersionUID = 1L;

        private String resource;

        public String getResource() {
            return resource;
        }

        public RateLimitException(String resource) {
            super(resource + " should not be visited so frequently");
            this.resource = resource;
        }

        @Override
        public synchronized Throwable fillInStackTrace() {
            return this;
        }
    }

    private static final ConcurrentMap<String, RateLimiter>
            resourceLimiterMap = Maps.newConcurrentMap();

    public static void updateResourceQps(String resource, double qps) {
        RateLimiter limiter = resourceLimiterMap.get(resource);
        if (limiter == null) {
            limiter = RateLimiter.create(qps);
            RateLimiter putByOtherThread
                    = resourceLimiterMap.putIfAbsent(resource, limiter);
            if (putByOtherThread != null) {
                limiter = putByOtherThread;
            }
        }
        limiter.setRate(qps);
    }

    public static void removeResource(String resource) {
        resourceLimiterMap.remove(resource);
    }

    public static void enter(String resource) throws RateLimitException {
        RateLimiter limiter = resourceLimiterMap.get(resource);
        if (limiter == null) {
            return;
        }
        if (!limiter.tryAcquire()) {
            throw new RateLimitException(resource);
        }
    }

    public static void exit(String resource) {
        //do nothing when use RateLimiter
    }
}

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