springcloud熔断器参数浅析

@GetMapping("/dept/{id}")
    @HystrixCommand(fallbackMethod = "fallback",
            commandProperties ={
                    @HystrixProperty(name = "circuitBreaker.enabled",value ="true"),
                    @HystrixProperty(name = "circuitBreaker.requestVolumeThreshold",value = "10"),
                    @HystrixProperty(name = "circuitBreaker.sleepWindowInMilliseconds",value = "10000"),
                    @HystrixProperty(name = "circuitBreaker.errorThresholdPercentage",value = "60")
            } )

    public Dept getById(@PathVariable("id") Long id) throws IOException {
        if (id<2){
            System.out.println("dept----8001");
            return deptService.findDeptById(id);
        }
        else {
            /*制造异常,引起服务降级*/
            throw new IOException();
        }


    }

• 当在一个时间窗口（sleepWindowInMilliseconds）内请求数量达到requestVolumeThreshold（10）个会进行判断熔断与否，请求中错误请求的比例到达errorThresholdPercentage（60%）,
  就打开熔断器，一律将请求交给降级服务，打开状态有个时间（sleepWindowInMilliseconds）来限制，过了这个时间就会进入
  半熔断状态，此时允许一部分请求访问未降级服务，如果调用正常服务全都成功或者达到了一定比例
  就会恢复到关闭状态，否则认为还有问题，就回到打开状态，限制时间刷新重置:
  
  还有其他@HystrixProperty:

 protected HystrixCommandProperties(HystrixCommandKey key, HystrixCommandProperties.Setter builder, String propertyPrefix) {
        this.key = key;
        this.circuitBreakerEnabled = getProperty(propertyPrefix, key, "circuitBreaker.enabled", builder.getCircuitBreakerEnabled(), default_circuitBreakerEnabled);
        this.circuitBreakerRequestVolumeThreshold = getProperty(propertyPrefix, key, "circuitBreaker.requestVolumeThreshold", builder.getCircuitBreakerRequestVolumeThreshold(), default_circuitBreakerRequestVolumeThreshold);
        this.circuitBreakerSleepWindowInMilliseconds = getProperty(propertyPrefix, key, "circuitBreaker.sleepWindowInMilliseconds", builder.getCircuitBreakerSleepWindowInMilliseconds(), default_circuitBreakerSleepWindowInMilliseconds);
        this.circuitBreakerErrorThresholdPercentage = getProperty(propertyPrefix, key, "circuitBreaker.errorThresholdPercentage", builder.getCircuitBreakerErrorThresholdPercentage(), default_circuitBreakerErrorThresholdPercentage);
        this.circuitBreakerForceOpen = getProperty(propertyPrefix, key, "circuitBreaker.forceOpen", builder.getCircuitBreakerForceOpen(), default_circuitBreakerForceOpen);
        this.circuitBreakerForceClosed = getProperty(propertyPrefix, key, "circuitBreaker.forceClosed", builder.getCircuitBreakerForceClosed(), default_circuitBreakerForceClosed);
        this.executionIsolationStrategy = getProperty(propertyPrefix, key, "execution.isolation.strategy", builder.getExecutionIsolationStrategy(), default_executionIsolationStrategy);
        this.executionTimeoutInMilliseconds = getProperty(propertyPrefix, key, "execution.isolation.thread.timeoutInMilliseconds", builder.getExecutionIsolationThreadTimeoutInMilliseconds(), default_executionTimeoutInMilliseconds);
        this.executionTimeoutEnabled = getProperty(propertyPrefix, key, "execution.timeout.enabled", builder.getExecutionTimeoutEnabled(), default_executionTimeoutEnabled);
        this.executionIsolationThreadInterruptOnTimeout = getProperty(propertyPrefix, key, "execution.isolation.thread.interruptOnTimeout", builder.getExecutionIsolationThreadInterruptOnTimeout(), default_executionIsolationThreadInterruptOnTimeout);
        this.executionIsolationThreadInterruptOnFutureCancel = getProperty(propertyPrefix, key, "execution.isolation.thread.interruptOnFutureCancel", builder.getExecutionIsolationThreadInterruptOnFutureCancel(), default_executionIsolationThreadInterruptOnFutureCancel);
        this.executionIsolationSemaphoreMaxConcurrentRequests = getProperty(propertyPrefix, key, "execution.isolation.semaphore.maxConcurrentRequests", builder.getExecutionIsolationSemaphoreMaxConcurrentRequests(), default_executionIsolationSemaphoreMaxConcurrentRequests);
        this.fallbackIsolationSemaphoreMax

都在这个类：
HystrixCommandProperties

• 当我快速访问了多次能引起错误的请求后，
• 
• 然后我发起了正常请求，会变为closed：
  
• =======================================

还有个值得注意的参数timeoutInMilliseconds，
即超时时间：
当A调用B服务时，可能因为网络或者业务复杂所以需要一些处理时间，如下单，支付等，如果超时时间太小，那么得到的结果总是服务降级后的错误页面，所以要合理配置。

然后服务模拟耗时处理：

结果访问正常url也是降级结果：

如果是消费方调用直接异常：


接下来设置为3秒超时（默认1s,小于2s），大于sleep的2s：

结果结果正常返回，查看请求用时：

表明sleep结束才返回的，问题解决。
当我用消费服务调用时，报了个错：

feign.RetryableException: Read timed out

在消费方添加配置：

#feign超时
DEPT-PROVIDER: #服务名
  ribbon:
    ReadTimeout: 60000
    ConnectTimeout: 60000
    MaxAutoRetries: 0
    MaxAutoRetriesNextServer: 1

其他属性意思参考：
http://www.imooc.com/article/76515
https://www.jianshu.com/p/138f92aa83dc