对HystrixCircuitBreaker源码的解析

public interface HystrixCircuitBreaker {

    public boolean allowRequest();

    public boolean isOpen();

    void markSuccess();

}

allowRequest：代表是否允许请求

isOpen：代表是否打开

markSuccess：关闭断路器

HystrixCircuitBreakerImpl实现了HystrixCircuitBreaker

public void markSuccess() {

if (circuitOpen.get()) {

//设置关闭

    if (circuitOpen.compareAndSet(true,false)) {

            metrics.resetStream();

    }

    }

}

下面说说open方法

public boolean isOpen() {

if (circuitOpen.get()) {

        return true;

}

    HealthCounts health =metrics.getHealthCounts();

//是否达到阈值，默认20

    if (health.getTotalRequests()< properties.circuitBreakerRequestVolumeThreshold().get()) {

        return false;

}

//是否达到错误阈值

if (health.getErrorPercentage()

return false;

}else {//打开开关

        if (circuitOpen.compareAndSet(false,true)) {//记录当前时间

            circuitOpenedOrLastTestedTime.set(System.currentTimeMillis());

            return true;

}else {

            return true;

    }

    }

}

public boolean allowRequest() {

//强制打开开关

if (properties.circuitBreakerForceOpen().get()) {

        return false;

}//强制关闭

if (properties.circuitBreakerForceClosed().get()) {

        isOpen();

        return true;

}

return !isOpen() || allowSingleTest();

}

1、如果开关已开，不允许访问，降级执行

2、还有allowSingleTest方法，咱们看看这个方法，实现是开启状态，如果当前时间大于休眠时间，此时处于半开状态，允许再次访问，若访问失败，则开启，若访问成功，则关闭。

public boolean allowSingleTest() {

long timeCircuitOpenedOrWasLastTested =circuitOpenedOrLastTestedTime.get();

    if (circuitOpen.get() && System.currentTimeMillis() > timeCircuitOpenedOrWasLastTested +properties.circuitBreakerSleepWindowInMilliseconds().get()) {

    if(circuitOpenedOrLastTestedTime.compareAndSet(timeCircuitOpenedOrWasLastTested, System.currentTimeMillis())) {

            return true;

    }

}

return false;

}