circuitBreaker.enabled 是否开启熔断 circuitBreaker.requestVolumeThreshold 熔断最低触发请求数阈值 circuitBreaker.sleepWindowInMilliseconds 产生熔断后恢复窗口 circuitBreaker.errorThresholdPercentage 错误率阈值 circuitBreaker.forceOpen 强制打开熔断 circuitBreaker.forceClosed 强制关闭熔断
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命令执行前调用circuitBreaker.attemptExecution()，正常情况下会执行返回true，但是如果发生熔断，则需要通过sleepWindows来进行恢复
public boolean attemptExecution() { if (properties.circuitBreakerForceOpen().get()) { return false; } if (properties.circuitBreakerForceClosed().get()) { return true; } if (circuitOpened.get() == -1) { return true; } else { if (isAfterSleepWindow()) { if (status.compareAndSet(Status.OPEN, Status.HALF_OPEN)) { //only the first request after sleep window should execute return true; } else { return false; } } else { return false; } } } 在新版本1.5.12中，会有一个后台线程订阅metrics流实时计算：
- 如果没有达到RequestVolume，则直接返回，不计算是否需要熔断
如果当前错误率大于设置的阈值，则触发熔断，状态由CLOSED切换到OPEN，并设置当前熔断的时间（用于后续SleepWindows判断使用）
if (hc.getTotalRequests() < properties.circuitBreakerRequestVolumeThreshold().get()) { // we are not past the minimum volume threshold for the stat window, // so no change to circuit status. // if it was CLOSED, it stays CLOSED // if it was half-open, we need to wait for a successful command execution // if it was open, we need to wait for sleep window to elapse } else { if (hc.getErrorPercentage() < properties.circuitBreakerErrorThresholdPercentage().get()) { //we are not past the minimum error threshold for the stat window, // so no change to circuit status. // if it was CLOSED, it stays CLOSED // if it was half-open, we need to wait for a successful command execution // if it was open, we need to wait for sleep window to elapse } else { // our failure rate is too high, we need to set the state to OPEN if (status.compareAndSet(Status.CLOSED, Status.OPEN)) { circuitOpened.set(System.currentTimeMillis()); } } }
// 执行成功后调用 public void markSuccess() { if (status.compareAndSet(Status.HALF_OPEN, Status.CLOSED)) { //This thread wins the race to close the circuit - it resets the stream to start it over from 0 metrics.resetStream(); Subscription previousSubscription = activeSubscription.get(); if (previousSubscription != null) { previousSubscription.unsubscribe(); } Subscription newSubscription = subscribeToStream(); activeSubscription.set(newSubscription); circuitOpened.set(-1L); } } // 执行失败后调用 public void markNonSuccess() { if (status.compareAndSet(Status.HALF_OPEN, Status.OPEN)) { //This thread wins the race to re-open the circuit - it resets the start time for the sleep window circuitOpened.set(System.currentTimeMillis()); } }