在Spring Cloud中，Feign和Ribbon在整合了Hystrix后，可能會出現首次調用失敗的問題
com.netflix.hystrix.exception.HystrixTimeoutException: null
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) [na:1.8.0_131]
at java.util.concurrent.FutureTask.runAndReset(FutureTask.java:308) [na:1.8.0_131]
at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$301(ScheduledThreadPoolExecutor.java:180) [na:1.8.0_131]
at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:294) [na:1.8.0_131]
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142) [na:1.8.0_131]
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617) [na:1.8.0_131]
at java.lang.Thread.run(Thread.java:748) [na:1.8.0_131]
產生的原因：
Hystrix默認的超時時間是1秒，如果超過這個時間尚未響應，將會進入fallback
第一次請求往往會比較慢，響應時間可能會大於1秒
解決的方法有3種：
（1）Hystrix的超時時間設置為5秒
hystrix.command.default.execution.isolation.thread.timeoutInMilliseconds=5000
（2）禁用Hystrix的超時時間
hystrix.command.default.execution.timeout.enabled
（3）禁用feign的hystrix
feign.hystrix.enabled=false