01. Hystrix 사용하기

Display → Product 연동 구간에 Circuit Breaker를 적용!

[display] build.gradle에 hystrix dependency추가

compile('org.springframework.cloud:spring-cloud-starter-netflix-hystrix')

[display] DisplayApplication에 @EnableCircuitBreaker추가

@EnableCircuitBreaker

[display] ProductRemoteServiceImp에 @HystrixCommand 추가

@HystrixCommand

02. Hystrix Fallback 적용하기

가. Fallback 적용하기

git checkout tags/step-2-hystrix-fallback -b step-2-hystrix-fallback

개요
- Display 서비스는 외부 Server인 Product API와 연동되어있음
- Product API에 장애가 나더라도 Display의 다른 서비스는 이상없이 동작하였으면 합니다
- Product API에 응답 오류인경우, Default값을 넣어 주고 싶습니다

[product] ProductController에서 항상 Exception 던지게 수정하기 (장애 상황 흉내)

@RestController
@RequestMapping("/products")
public class ProductController {

    @GetMapping(path = "{productId}")
    public String getProductInfo(@PathVariable String productId) {
        // return "[product id = " + productId + " at " + System.currentTimeMillis() + "]";
        throw new RuntimeException("I/O Exception");
    }
}

[display] ProductRemoteServiceImp에 Fallback Method 작성하기

@Service
public class ProductRemoteServiceImpl implements ProductRemoteService {

    private static final String url = "http://localhost:8082/products/";
    private final RestTemplate restTemplate;

    public ProductRemoteServiceImpl(RestTemplate restTemplate) {
        this.restTemplate = restTemplate;
    }

    @Override
    @HystrixCommand(fallbackMethod = "getProductInfoFallback")
    public String getProductInfo(String productId) {
        return this.restTemplate.getForObject(url + productId, String.class);
    }

    public String getProductInfoFallback(String productId) {
        return "[ this product is sold out ]";
    }
}

Product → Display 호출 확인
- - Product 확인
    http://localhost:8082/products/22222
  - Display 확인
    http://localhost:8081/displays/11111

나. Fallback 원인 출력하기

git checkout tags/step-2-hystrix-fallback2 -b step-2-hystrix-fallback2

[display] ProductRemoteServiceImp에 Fallback Method 에 Throwable추가

@Service
public class ProductRemoteServiceImpl implements ProductRemoteService {

    private static final String url = "http://localhost:8082/products/";
    private final RestTemplate restTemplate;

    public ProductRemoteServiceImpl(RestTemplate restTemplate) {
        this.restTemplate = restTemplate;
    }

    @Override
    @HystrixCommand(fallbackMethod = "getProductInfoFallback")
    public String getProductInfo(String productId) {
        return this.restTemplate.getForObject(url + productId, String.class);
    }

    public String getProductInfoFallback(String productId, Throwable t) {
        System.out.println("t = " + t);
        return "[ this product is sold out ]";
    }
}

Display 호출 확인

http://localhost:8081/displays/11111

2020-02-25 11:32:22.068  INFO 69092 --- [io-8081-exec-10] o.a.c.c.C.[Tomcat].[localhost].[/]       : Initializing Spring FrameworkServlet 'dispatcherServlet'
2020-02-25 11:32:22.068  INFO 69092 --- [io-8081-exec-10] o.s.web.servlet.DispatcherServlet        : FrameworkServlet 'dispatcherServlet': initialization started
2020-02-25 11:32:22.174  INFO 69092 --- [io-8081-exec-10] o.s.web.servlet.DispatcherServlet        : FrameworkServlet 'dispatcherServlet': initialization completed in 106 ms
t = org.springframework.web.client.HttpServerErrorException: 500 null

03. Hystrix로 Timeout 처리하기

04. Hystrix Circuit Open 테스트

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실습 Step-2. Hystrix 사용하기