spring cloud学习——13. Circuit Breaker: Hystrix Clients

13. CircuitBreaker: Hystrix Clients

Hystrix

断路器

13.1 How to Include Hystrix

服务消费者microservice-customer-movie-ribbon-withHistrict2上面写断路器。

如果服务提供者microservice-provider-user异常，就会发生短路，执行写好的程序

1.启动类增加注解@EnableCircuitBreaker

2.controller

@controller
@RestController
public class UseDemoController {

	@Autowired
	private RestTemplate restTemplate;
	
	@RequestMapping("/demo")
	@HystrixCommand(fallbackMethod = "findByIdFallback")//设置断路器，如果连接不上，就执行断路器“findByIdFallback”
	public String useDemo() {
		return restTemplate.getForObject("http://microservice-provider-user/demo/dd", String.class);//参数1使eureka的service-id,是个虚拟主机名,可以用eureka.instance.secure.virtual-host-name定义,如果不是https的，就用eureka.instance.virtual-host-name
	}
	
	//断路器方法
	public String findByIdFallback() {
		return " ----findByIdFallback---";
	}
}

13.2Propagating the Security Context orusing Spring Scopes(传播安全上下文，和springscopes)

execution.isolation.strategy  

This property indicates which isolation strategyHystrixCommand.run() executes with，one of the following two choices：隔离策略

THREAD——it executes on a separate thread and concurrent requests are limitedby the number of threads in the thread-pool（它是一个单独的线程上执行，并发请求受线程池中的线程数量的限制，默认策略）

SEMAPHORE——it executes on the calling thread and concurrent requests arelimited by the semaphore count（它在调用线程上执行，并发请求受到信号量计数的限制）

hystrix.shareSecurityContext ：spring security上下文

13.3 Health Indicator

/health 暴露了连接的断路器的状态

13.4 Hystrix Metrics Stream

hystrix.stream作为管理端口