springcloud之Hystrix

发表于 2020-12-15 更新于 2020-12-30 分类于 springcloud

springcloud之Hystrix

Spring Cloud Netflix Hystrix – the fault tolerance library, use it for circuit breaker (断路器)

tolerate failures up to a threshold and then leaves the circuit open - forward all subsequent calls to the fallback method, to prevent future failures

Hystrix

Add e @EnableCircuitBreaker

For the Circuit Breaker to work, Hystix will scan @Component or @Service annotated classes for @HystixCommand annotated methods, implement a proxy for it and monitor its calls.

Eg:

@SpringBootApplication
@EnableCircuitBreaker
public class RestConsumerApplication {
    public static void main(String[] args) {
        SpringApplication.run(RestConsumerApplication.class, args);
    }
}

@Service
public class GreetingService {
    @HystrixCommand(fallbackMethod = "defaultGreeting")
    public String getGreeting(String username) {
        return new RestTemplate()
          .getForObject("http://localhost:9090/greeting/{username}", 
          String.class, username);
    }
 
    private String defaultGreeting(String username) {
        return "Hello User!";
    }
}

Hystrix with Feign

@FeignClient(
  name = "rest-producer"
  url = "http://localhost:9090", 
  fallback = GreetingClient.GreetingClientFallback.class
)
public interface GreetingClient extends GreetingController {
     
    @Component
    public static class GreetingClientFallback implements GreetingController {
 
        @Override
        public String greeting(@PathVariable("username") String username) {
            return "Hello User!";
        }
    }
}


@SpringBootApplication
@EnableCircuitBreaker
@EnableFeignClients
public class RestConsumerFeignApplication {
     
    public static void main(String[] args) {
        SpringApplication.run(RestConsumerFeignApplication.class, args);
    }
}

hystrix dashboard

A nice optional feature of Hystrix is the ability to monitor its status on a dashboard.

https://www.baeldung.com/spring-cloud-netflix-hystrix