Hystrix报错java.util.concurrent.TimeoutException: null

完整错误如下：

java.util.concurrent.TimeoutException: null
    at com.netflix.hystrix.AbstractCommand.handleTimeoutViaFallback(AbstractCommand.java:997) ~[hystrix-core-1.5.18.jar:1.5.18]
    at com.netflix.hystrix.AbstractCommand.access$500(AbstractCommand.java:60) ~[hystrix-core-1.5.18.jar:1.5.18]
    at com.netflix.hystrix.AbstractCommand$12.call(AbstractCommand.java:609) ~[hystrix-core-1.5.18.jar:1.5.18]
    at com.netflix.hystrix.AbstractCommand$12.call(AbstractCommand.java:601) ~[hystrix-core-1.5.18.jar:1.5.18]
    at rx.internal.operators.OperatorOnErrorResumeNextViaFunction$4.onError(OperatorOnErrorResumeNextViaFunction.java:140) ~[rxjava-1.3.8.jar:1.3.8]
    at rx.internal.operators.OnSubscribeDoOnEach$DoOnEachSubscriber.onError(OnSubscribeDoOnEach.java:87) ~[rxjava-1.3.8.jar:1.3.8]
    at rx.internal.operators.OnSubscribeDoOnEach$DoOnEachSubscriber.onError(OnSubscribeDoOnEach.java:87) ~[rxjava-1.3.8.jar:1.3.8]
    at com.netflix.hystrix.AbstractCommand$HystrixObservableTimeoutOperator$1.run(AbstractCommand.java:1142) ~[hystrix-core-1.5.18.jar:1.5.18]
    at com.netflix.hystrix.strategy.concurrency.HystrixContextRunnable$1.call(HystrixContextRunnable.java:41) ~[hystrix-core-1.5.18.jar:1.5.18]
    at com.netflix.hystrix.strategy.concurrency.HystrixContextRunnable$1.call(HystrixContextRunnable.java:37) ~[hystrix-core-1.5.18.jar:1.5.18]
    at com.netflix.hystrix.strategy.concurrency.HystrixContextRunnable.run(HystrixContextRunnable.java:57) ~[hystrix-core-1.5.18.jar:1.5.18]
    at com.netflix.hystrix.AbstractCommand$HystrixObservableTimeoutOperator$2.tick(AbstractCommand.java:1159) ~[hystrix-core-1.5.18.jar:1.5.18]
    at com.netflix.hystrix.util.HystrixTimer$1.run(HystrixTimer.java:99) ~[hystrix-core-1.5.18.jar:1.5.18]
    at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511) ~[?:1.8.0_221]
    at java.util.concurrent.FutureTask.runAndReset(FutureTask.java:308) ~[?:1.8.0_221]
    at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$301(ScheduledThreadPoolExecutor.java:180) ~[?:1.8.0_221]
    at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:294) ~[?:1.8.0_221]
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) ~[?:1.8.0_221]
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) ~[?:1.8.0_221]
    at java.lang.Thread.run(Thread.java:748) [?:1.8.0_221]

问了度娘，有关闭断路功能的，有断路时间调长的，完全不在点上，我的目的是测试Hystrix断路器功能，都关闭了，我还咋验证。后来发现在这个报错之上还有一行错误：

com.netflix.hystrix.contrib.javanica.command.GenericCommand.getFallback 80 - failed to processed fallback is the method: 'failHi'. 

调试com.netflix.hystrix.contrib.javanica.command.GenericCommand.getFallback方法，发现是断路@HystrixCommand注解定义fallbackMethod方法反射调用failHi失败，再次调试报错的failHi方法，最终发现是failHi方法中出现了RuntimeException异常，错误的实例代码如下：

@HystrixCommand(fallbackMethod = "failHi")
@ResponseBody
@GetMapping("/hi3")
public String hi3() {
    return restTemplate.getForObject("http://127.0.0.1:" + port + "/res", String.class);
}

public String failHi() {
    try {
        return doThings();
    } catch (Exception e) {
        throw new RuntimeException("失败，" + e.getMessage());
    }
}