Spring Cloud Netflix Hystrix
RECOMMEND POSTS BEFORE THIS
1. Netflix Hystrix
마이크로서비스 아키텍처(microservice architecture)를 성공적으로 구축한 넷플릭스(netflix)가 제공하는 OSS(open source software)입니다.
Hystrix 컴포넌트는 애너테이션과 설정만으로 손쉽게 회로 차단기(circuit breaker) 패턴을 적용할 수 있습니다.
서비스 사이에 전파되는 장애를 차단하여 서비스 일부가 망가지더라도 시스템은 정상적 혹은 부분적으로 운영할 수 있도록 돕습니다.
2. Practice
FeignClient와 함께 연동한 실습을 수행하였습니다.
FeignClient 내부엔 다음과 같은 의존성이 존재하여 별도로 Hystrix 컴포넌트에 대한 의존성을 추가하지 않아도 됩니다.
<dependency>
<groupId>io.github.openfeign</groupId>
<artifactId>feign-hystrix</artifactId>
<version>10.10.1</version>
<scope>compile</scope>
</dependency>
2.1. Context of Practice
다음과 같은 실습 환경을 구축하였습니다.
- 클라이언트(client) 역할은
JUnit테스트 코드가 수행합니다. 서비스A는 회로 차단기가 적용되어 있습니다.서비스A가서비스B로 API 요청을 수행합니다.- 두 경로로 요청을 수행합니다.
/timeout-서비스B는 스레드를 정지시켜 의도적으로 타임아웃(timeout)을 발생시킵니다./exception-서비스B는 의도적으로 예외를 던집니다.
서비스A는 예외를 전달 받지만 이를 대체할 응답(fallback plan)을 대신 클라이언트에게 전달합니다.- 클라이언트는 예외 대신
서비스A가 전달한 대체 응답을 전달 받습니다.
2.2. Implemantation of Service A
2.2.1. application.yml
feign.hystrix.enabled=true설정을 추가합니다.- 타임아웃이 발생하기 쉽게 기다리는 시간을 5초로 설정합니다.
feign:
hystrix:
enabled: true
client:
config:
default:
connect-timeout: 5000
read-timeout: 5000
2.2.2. BlogController Class
- 요청을 그대로
서비스B에게 전달합니다.
package cloud.in.action.controller;
import cloud.in.action.proxy.BlogClient;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;
@RestController
public class BlogController {
private final BlogClient blogClient;
public BlogController(BlogClient blogClient) {
this.blogClient = blogClient;
}
@GetMapping(value = "/timeout")
public String requestWithTimeoutException() {
return blogClient.requestWithTimeoutException();
}
@GetMapping(value = "/exception")
public String requestWithIntentionalException() {
return blogClient.requestWithIntentionalException();
}
}
2.2.3. BlogClient Interface and Fallback
feign.hystrix.* 패키지에 속한 FallbackFactory 클래스를 사용해야 합니다.
자세한 내용은 Incompatible FallbackFactory Instance Exception 포스트를 참조하시길 바랍니다.
BlogClient는서비스B에게 API 요청을 수행합니다.서비스B에 문제가 발생하여 회로 차단기가 회로를 열면 대체 응답이 반환됩니다.- 대체 응답에 대한 책임은
BlogClientFallbackFactory를 통해 생성된 객체에게 위임합니다. BlogClientFallbackFactory는BlogClient에 문제가 생겼을 때를 대비한BlogClientFallbackPlan객체를 생성합니다.BlogClientFallbackPlan클래스는BlogClient인터페이스를 구현하여 에러 발생 시 각 메소드 별 적절한 응답을 반환합니다.
package cloud.in.action.proxy;
import feign.hystrix.FallbackFactory;
import lombok.extern.log4j.Log4j2;
import org.springframework.cloud.openfeign.FeignClient;
import org.springframework.stereotype.Component;
import org.springframework.web.bind.annotation.GetMapping;
@FeignClient(
name = "blog-client",
url = "http://b-service:8080",
fallbackFactory = BlogClientFallbackFactory.class
)
public interface BlogClient {
@GetMapping(path = "/timeout")
String requestWithTimeoutException();
@GetMapping(path = "/exception")
String requestWithIntentionalException();
}
@Log4j2
@Component
class BlogClientFallbackFactory implements FallbackFactory<BlogClient> {
@Override
public BlogClient create(Throwable cause) {
log.error(cause.getMessage(), cause);
return new BlogClientFallbackPlan();
}
class BlogClientFallbackPlan implements BlogClient {
@Override
public String requestWithTimeoutException() {
return "timeout fallback";
}
@Override
public String requestWithIntentionalException() {
return "implicit exception fallback";
}
}
}
2.3. Implemantation of Service B
2.3.1. BlogController Class
- 고의적으로 예외를 발생시키는 컨트롤러입니다.
/timeout경로는 10초 간 스레드를 정지하여 타임아웃 예외를 발생시킵니다./exception경로는 일부러 런타임 예외를 발생시킵니다.
package cloud.in.action.controller;
import lombok.extern.log4j.Log4j2;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;
@Log4j2
@RestController
public class BlogController {
@GetMapping(value = "/timeout")
public String requestWithTimeoutException() {
try {
Thread.sleep(10000);
} catch (Exception e) {
log.error(e.getMessage(), e);
}
return "no time out occur";
}
private boolean implementationException() {
return true;
}
@GetMapping(value = "/exception")
public String requestWithIntentionalException() {
if (implementationException()) {
throw new RuntimeException("exception occur");
}
return "no exception occur";
}
}
3. Test
도커 컴포즈(docker compose)로 테스트 환경을 구축합니다.
3.1. docker-compose.yml
version: "3.9"
services:
a-service:
build: ./a-service
ports:
- "8080:8080"
b-service:
build: ./b-service
ports:
- "8081:8080"
3.2. Run Docker Compose
$ docker-compose up
[+] Building 301.1s (23/23) FINISHED
=> [2021-03-13-spring-cloud-netflix-hystrix-b-service internal] load build definition from Dockerfile 0.0s
=> => transferring dockerfile: 392B 0.0s
=> [2021-03-13-spring-cloud-netflix-hystrix-a-service internal] load build definition from Dockerfile 0.0s
=> => transferring dockerfile: 392B 0.0s
=> [2021-03-13-spring-cloud-netflix-hystrix-b-service internal] load .dockerignore 0.0s
=> => transferring context: 2B 0.0s
=> [2021-03-13-spring-cloud-netflix-hystrix-a-service internal] load .dockerignore 0.0s
=> => transferring context: 2B 0.0s
=> [2021-03-13-spring-cloud-netflix-hystrix-a-service internal] load metadata for docker.io/library/openjdk:11-jdk-slim-buster 4.9s
=> [2021-03-13-spring-cloud-netflix-hystrix-a-service internal] load metadata for docker.io/library/maven:3.8.6-jdk-11 4.8s
=> [2021-03-13-spring-cloud-netflix-hystrix-a-service stage-1 1/3] FROM docker.io/library/openjdk:11-jdk-slim-buster@sha256:863ce6f3c27a0a50b458227f23beadda1e7178cda0971fa42b50b05d9a5dcf55 0.0s
=> [2021-03-13-spring-cloud-netflix-hystrix-a-service maven_build 1/6] FROM docker.io/library/maven:3.8.6-jdk-11@sha256:805f366910aea2a91ed263654d23df58bd239f218b2f9562ff51305be81fa215 0.0s
=> [2021-03-13-spring-cloud-netflix-hystrix-b-service internal] load build context 0.1s
=> => transferring context: 4.10kB 0.0s
=> [2021-03-13-spring-cloud-netflix-hystrix-a-service internal] load build context 0.0s
=> => transferring context: 6.62kB 0.0s
=> CACHED [2021-03-13-spring-cloud-netflix-hystrix-b-service maven_build 2/6] WORKDIR /build 0.0s
=> [2021-03-13-spring-cloud-netflix-hystrix-a-service maven_build 3/6] COPY pom.xml . 0.1s
=> [2021-03-13-spring-cloud-netflix-hystrix-b-service maven_build 3/6] COPY pom.xml . 0.1s
=> [2021-03-13-spring-cloud-netflix-hystrix-b-service maven_build 4/6] RUN mvn dependency:go-offline 263.9s
=> [2021-03-13-spring-cloud-netflix-hystrix-a-service maven_build 4/6] RUN mvn dependency:go-offline 284.9s
=> [2021-03-13-spring-cloud-netflix-hystrix-b-service maven_build 5/6] COPY src ./src 0.1s
=> [2021-03-13-spring-cloud-netflix-hystrix-b-service maven_build 6/6] RUN mvn package -Dmaven.test.skip=true 3.4s
=> CACHED [2021-03-13-spring-cloud-netflix-hystrix-b-service stage-1 2/3] WORKDIR /app 0.0s
=> [2021-03-13-spring-cloud-netflix-hystrix-b-service stage-1 3/3] COPY --from=MAVEN_BUILD /build/target/*.jar ./app.jar 0.1s
=> [2021-03-13-spring-cloud-netflix-hystrix-a-service] exporting to image 0.4s
=> => exporting layers 0.2s
=> => writing image sha256:542d91290686251ebcfd804bdb4b544399941fa94fdcac65d79cffec43aef94f 0.0s
=> => naming to docker.io/library/2021-03-13-spring-cloud-netflix-hystrix-b-service 0.0s
=> => writing image sha256:84a68c227190b100af3037c0519cd5eb39cc9b705c3ca8d8f070cdf91555ffe9 0.0s
=> => naming to docker.io/library/2021-03-13-spring-cloud-netflix-hystrix-a-service 0.0s
=> [2021-03-13-spring-cloud-netflix-hystrix-a-service maven_build 5/6] COPY src ./src 0.1s
=> [2021-03-13-spring-cloud-netflix-hystrix-a-service maven_build 6/6] RUN mvn package -Dmaven.test.skip=true 10.3s
=> [2021-03-13-spring-cloud-netflix-hystrix-a-service stage-1 3/3] COPY --from=MAVEN_BUILD /build/target/*.jar ./app.jar 0.1s
[+] Running 3/3
- Network 2021-03-13-spring-cloud-netflix-hystrix_default Created 0.0s
- Container 2021-03-13-spring-cloud-netflix-hystrix-a-service-1 Created 0.1s
- Container 2021-03-13-spring-cloud-netflix-hystrix-b-service-1 Created 0.1s
3.3. Run Test Code
테스트 코드는 서비스A 모듈에 존재합니다.
- 테스트에서 타임아웃이 발생하지 않도록
connectTimeout,readTimeout을 100초씩 설정합니다. - 테스트를 위한
FeignClient사용 시 회로 차단기가 동작하지 않도록 설정합니다.
package cloud.in.action;
import lombok.extern.log4j.Log4j2;
import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.cloud.openfeign.FeignClient;
import org.springframework.web.bind.annotation.GetMapping;
@FeignClient(name = "test-client", url = "http://localhost:8080")
interface TestClient {
@GetMapping(path = "/timeout")
String requestWithTimeoutException();
@GetMapping(path = "/exception")
String requestWithIntentionalException();
}
@Log4j2
@SpringBootTest(value = {
"feign.hystrix.enabled=false",
"feign.client.config.default.connect-timeout=100000",
"feign.client.config.default.read-timeout=100000"
})
class AServiceApplicationTests {
@Autowired
private TestClient testClient;
@Test
void request_api_expect_without_exception() {
log.info(testClient.requestWithTimeoutException());
log.info(testClient.requestWithIntentionalException());
}
}
Test Result
서비스A로 요청한 두 경로 모두BlogClientFallbackPlan객체에 의해 대체된 응답을 전달 받습니다.
2023-02-16 00:39:10.921 INFO 22208 --- [ main] c.in.action.AServiceApplicationTests : timeout fallback
2023-02-16 00:39:11.000 INFO 22208 --- [ main] c.in.action.AServiceApplicationTests : implicit exception fallback
Error Log in Service A and Service B
서비스A는netflix-hystrix-a-service입니다.서비스B는netflix-hystrix-b-service입니다.서비스A는서비스B의 요청을 기다리다 타임아웃이 발생합니다.- 해당 예외는
HystrixTimeoutException으로 전달됩니다.
- 해당 예외는
서비스B는 의도적인 예외를 반환합니다.- 로그 내용 - java.lang.RuntimeException: exception occur
서비스A는서비스B의 예외를 전달 받고 관련 로그를 출력합니다.- 로그 내용 - feign.FeignException$InternalServerError: [500] during [GET] to [http://b-service:8080/exception]
- 해당 예외 처리 스택을 보면
Hystrix컴포넌트가 상위 메소드에 있음을 알 수 있습니다.
2021-03-13-spring-cloud-netflix-hystrix-a-service-1 | 2023-02-15 15:39:10.891 ERROR 1 --- [ HystrixTimer-1] c.i.a.proxy.BlogClientFallbackFactory : null
2021-03-13-spring-cloud-netflix-hystrix-a-service-1 |
2021-03-13-spring-cloud-netflix-hystrix-a-service-1 | com.netflix.hystrix.exception.HystrixTimeoutException: null
2021-03-13-spring-cloud-netflix-hystrix-a-service-1 | at com.netflix.hystrix.AbstractCommand$HystrixObservableTimeoutOperator$1.run(AbstractCommand.java:1142) ~[hystrix-core-1.5.18.jar!/:1.5.18]
2021-03-13-spring-cloud-netflix-hystrix-a-service-1 | at com.netflix.hystrix.strategy.concurrency.HystrixContextRunnable$1.call(HystrixContextRunnable.java:41) ~[hystrix-core-1.5.18.jar!/:1.5.18]
2021-03-13-spring-cloud-netflix-hystrix-a-service-1 | at com.netflix.hystrix.strategy.concurrency.HystrixContextRunnable$1.call(HystrixContextRunnable.java:37) ~[hystrix-core-1.5.18.jar!/:1.5.18]
2021-03-13-spring-cloud-netflix-hystrix-a-service-1 | at com.netflix.hystrix.strategy.concurrency.HystrixContextRunnable.run(HystrixContextRunnable.java:57) ~[hystrix-core-1.5.18.jar!/:1.5.18]
2021-03-13-spring-cloud-netflix-hystrix-a-service-1 | at com.netflix.hystrix.AbstractCommand$HystrixObservableTimeoutOperator$2.tick(AbstractCommand.java:1159) ~[hystrix-core-1.5.18.jar!/:1.5.18]
2021-03-13-spring-cloud-netflix-hystrix-a-service-1 | at com.netflix.hystrix.util.HystrixTimer$1.run(HystrixTimer.java:99) ~[hystrix-core-1.5.18.jar!/:1.5.18]
2021-03-13-spring-cloud-netflix-hystrix-a-service-1 | at java.base/java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:515) ~[na:na]
...
2021-03-13-spring-cloud-netflix-hystrix-b-service-1 | 2023-02-15 15:39:10.940 ERROR 1 --- [nio-8080-exec-2] o.a.c.c.C.[.[.[/].[dispatcherServlet] : Servlet.service() for servlet [dispatcherServlet] in context with path [] threw exception [Request processing failed; nested exception is java.lang.RuntimeException: exception occur] with root cause
2021-03-13-spring-cloud-netflix-hystrix-b-service-1 |
2021-03-13-spring-cloud-netflix-hystrix-b-service-1 | java.lang.RuntimeException: exception occur
2021-03-13-spring-cloud-netflix-hystrix-b-service-1 | at cloud.in.action.controller.BlogController.requestWithIntentionalException(BlogController.java:28) ~[classes!/:0.0.1-SNAPSHOT]
2021-03-13-spring-cloud-netflix-hystrix-b-service-1 | at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:na]
2021-03-13-spring-cloud-netflix-hystrix-b-service-1 | at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:na]
2021-03-13-spring-cloud-netflix-hystrix-b-service-1 | at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:na]
2021-03-13-spring-cloud-netflix-hystrix-b-service-1 | at java.base/java.lang.reflect.Method.invoke(Method.java:566) ~[na:na]
2021-03-13-spring-cloud-netflix-hystrix-b-service-1 | at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:190) ~[spring-web-5.2.6.RELEASE.jar!/:5.2.6.RELEASE]
2021-03-13-spring-cloud-netflix-hystrix-b-service-1 | at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:138) ~[spring-web-5.2.6.RELEASE.jar!/:5.2.6.RELEASE]
2021-03-13-spring-cloud-netflix-hystrix-b-service-1 | at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:105) ~[spring-webmvc-5.2.6.RELEASE.jar!/:5.2.6.RELEASE]
2021-03-13-spring-cloud-netflix-hystrix-b-service-1 | at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:879) ~[spring-webmvc-5.2.6.RELEASE.jar!/:5.2.6.RELEASE]
2021-03-13-spring-cloud-netflix-hystrix-b-service-1 | at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:793) ~[spring-webmvc-5.2.6.RELEASE.jar!/:5.2.6.RELEASE]
...
2021-03-13-spring-cloud-netflix-hystrix-a-service-1 | 2023-02-15 15:39:10.995 ERROR 1 --- [x-blog-client-2] c.i.a.proxy.BlogClientFallbackFactory : [500] during [GET] to [http://b-service:8080/exception] [BlogClient#requestWithIntentionalException()]: [{"timestamp":"2023-02-15T15:39:10.948+0000","status":500,"error":"Internal Server Error","message":"exception occur","path":"/exception"}]
2021-03-13-spring-cloud-netflix-hystrix-a-service-1 |
2021-03-13-spring-cloud-netflix-hystrix-a-service-1 | feign.FeignException$InternalServerError: [500] during [GET] to [http://b-service:8080/exception] [BlogClient#requestWithIntentionalException()]: [{"timestamp":"2023-02-15T15:39:10.948+0000","status":500,"error":"Internal Server Error","message":"exception occur","path":"/exception"}]
2021-03-13-spring-cloud-netflix-hystrix-a-service-1 | at feign.FeignException.serverErrorStatus(FeignException.java:231) ~[feign-core-10.10.1.jar!/:na]
2021-03-13-spring-cloud-netflix-hystrix-a-service-1 | at feign.FeignException.errorStatus(FeignException.java:180) ~[feign-core-10.10.1.jar!/:na]
2021-03-13-spring-cloud-netflix-hystrix-a-service-1 | at feign.FeignException.errorStatus(FeignException.java:169) ~[feign-core-10.10.1.jar!/:na]
2021-03-13-spring-cloud-netflix-hystrix-a-service-1 | at feign.codec.ErrorDecoder$Default.decode(ErrorDecoder.java:92) ~[feign-core-10.10.1.jar!/:na]
2021-03-13-spring-cloud-netflix-hystrix-a-service-1 | at feign.AsyncResponseHandler.handleResponse(AsyncResponseHandler.java:96) ~[feign-core-10.10.1.jar!/:na]
2021-03-13-spring-cloud-netflix-hystrix-a-service-1 | at feign.SynchronousMethodHandler.executeAndDecode(SynchronousMethodHandler.java:138) ~[feign-core-10.10.1.jar!/:na]
2021-03-13-spring-cloud-netflix-hystrix-a-service-1 | at feign.SynchronousMethodHandler.invoke(SynchronousMethodHandler.java:89) ~[feign-core-10.10.1.jar!/:na]
2021-03-13-spring-cloud-netflix-hystrix-a-service-1 | at feign.hystrix.HystrixInvocationHandler$1.run(HystrixInvocationHandler.java:109) ~[feign-hystrix-10.10.1.jar!/:na]
2021-03-13-spring-cloud-netflix-hystrix-a-service-1 | at com.netflix.hystrix.HystrixCommand$2.call(HystrixCommand.java:302) ~[hystrix-core-1.5.18.jar!/:1.5.18]
2021-03-13-spring-cloud-netflix-hystrix-a-service-1 | at com.netflix.hystrix.HystrixCommand$2.call(HystrixCommand.java:298) ~[hystrix-core-1.5.18.jar!/:1.5.18]
2021-03-13-spring-cloud-netflix-hystrix-a-service-1 | at rx.internal.operators.OnSubscribeDefer.call(OnSubscribeDefer.java:46) ~[rxjava-1.3.8.jar!/:1.3.8]
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