유레카 클라이언트 ( Eureka Client )

Spring Cloud 아키텍처 관계도

출처 : https://spring.io/cloud

개발환경

• JDK : Zulu JDK 17.0.10
• SpringBoot : 3.2.3
  • org.springframework.boot:spring-boot-starter-web
  • org.springframework.cloud:spring-cloud-starter-netflix-eureka-client
• SpringBoot Eureka Client : 현재 최신버전 4.1.0
• build tools : Gradle

Spring Cloud 버전과 Spring Boot 버전 및 JDK 의 버전 호환성

• 출처

https://spring.io/projects/spring-cloud#overview  
https://github.com/spring-projects/spring-framework/wiki/Spring-Framework-Versions

Release Train	Spring Boot Generation	JDK 버전 ( LTS )	비고
2023.0.x aka Leyton	3.2.x	JDK 17
2022.0.x aka Kilburn	3.0.x, 3.1.x (Starting with 2022.0.3)	JDK 17
2021.0.x aka Jubilee	2.6.x, 2.7.x (Starting with 2021.0.3)	JDK 11
2020.0.x aka Ilford	2.4.x, 2.5.x (Starting with 2020.0.3)	JDK 11
Hoxton	2.2.x, 2.3.x (Starting with SR5)	JDK 8, 11
Greenwich	2.1.x	JDK 8	지원종료
Finchley	2.0.x	JDK 8	지원종료
Edgware	1.5.x	JDK 6, 7, 8	지원종료
Dalston	1.5.x	JDK 6, 7, 8	지원종료

Source

• 유레카 서버(Erureka Client)의 개발은 간단하다.
• 기본적으로 3개의 파일만 필요하다.
  • build.gradle, EurekaClientApplication.java,application.yml

build.gradle

plugins {
	id 'java'
	id 'org.springframework.boot' version '3.2.3'
	id 'io.spring.dependency-management' version '1.1.4'
}

group = 'octopus'
version = '0.0.1-SNAPSHOT'

java {
	sourceCompatibility = '17'
}

repositories {
	mavenCentral()
}

ext {
	set('springCloudVersion', "2023.0.0")         // 스프링 클라우드 버전
}

dependencies {
	implementation 'org.springframework.boot:spring-boot-starter-web'
	implementation 'org.springframework.cloud:spring-cloud-starter-netflix-eureka-client'
	testImplementation 'org.springframework.boot:spring-boot-starter-test'
}

dependencyManagement {
	imports {
		mavenBom "org.springframework.cloud:spring-cloud-dependencies:${springCloudVersion}"
	}
}

tasks.named('test') {
	useJUnitPlatform()
}

EurekaClientApplication.java

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.discovery.EnableDiscoveryClient;

@SpringBootApplication
@EnableDiscoveryClient
// @EnableEurekaClient        // Spring Cloud Version 2022.0 이상의 경우 사용할 수 없음.
public class EurekaClientApplication {

  public static void main(String[] args) {
    SpringApplication.run(EurekaClientApplication.class, args);
  }

}

application.yml

spring:
  application:
    name: EurekaClient

server:
  port: 9191

eureka:
  client:
    fetch-registry: true
    register-with-eureka: true
    service-url:
      defaultZone: http://localhost:8761/eureka/         #Eureka Server ??
  instance:
    hostname: localhost

Build

프로젝트 디렉토리에서 실행한다.

$ ./gradlew bootJar

실행

파일 찾기

$ find . -name '*.jar'                                   
./gradle/wrapper/gradle-wrapper.jar
./build/libs/EurekaClient-0.0.1-SNAPSHOT.jar

jar 실행

• [프로젝트 디렉토리]/build/libs 폴더에 Build 됨.
• java -jar EurekaClient-0.0.1-SNAPSHOT.jar

# java -jar ./workspace/EurekaServer/build/libs/EurekaClient-0.0.1-SNAPSHOT.jar
# java -jar EurekaClient-0.0.1-SNAPSHOT.jar                               

  .   ____          _            __ _ _
 /\\ / ___'_ __ _ _(_)_ __  __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
 \\/  ___)| |_)| | | | | || (_| |  ) ) ) )
  '  |____| .__|_| |_|_| |_\__, | / / / /
 =========|_|==============|___/=/_/_/_/
 :: Spring Boot ::                (v3.2.3)

Git Push

git init
git add README.md
git commit -m "first commit"
git branch -M main
git remote add origin https://github.com/hermeswing/EurekaClient.git
git push -u origin main

오류

org.springframework.context.ApplicationContextException: Failed to start bean 'eurekaAutoServiceRegistration'
	at org.springframework.context.support.DefaultLifecycleProcessor.doStart(DefaultLifecycleProcessor.java:291) ~[spring-context-6.1.4.jar:6.1.4]
	at org.springframework.context.support.DefaultLifecycleProcessor$LifecycleGroup.start(DefaultLifecycleProcessor.java:471) ~[spring-context-6.1.4.jar:6.1.4]
	at java.base/java.lang.Iterable.forEach(Iterable.java:75) ~[na:na]
	at org.springframework.context.support.DefaultLifecycleProcessor.startBeans(DefaultLifecycleProcessor.java:260) ~[spring-context-6.1.4.jar:6.1.4]
	at org.springframework.context.support.DefaultLifecycleProcessor.onRefresh(DefaultLifecycleProcessor.java:205) ~[spring-context-6.1.4.jar:6.1.4]
	at org.springframework.context.support.AbstractApplicationContext.finishRefresh(AbstractApplicationContext.java:978) ~[spring-context-6.1.4.jar:6.1.4]
	at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:627) ~[spring-context-6.1.4.jar:6.1.4]
	at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:754) ~[spring-boot-3.2.3.jar:3.2.3]
	at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:456) ~[spring-boot-3.2.3.jar:3.2.3]
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:334) ~[spring-boot-3.2.3.jar:3.2.3]
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:1354) ~[spring-boot-3.2.3.jar:3.2.3]
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:1343) ~[spring-boot-3.2.3.jar:3.2.3]
	at octopus.EurekaClientApplication.main(EurekaClientApplication.java:10) ~[main/:na]
Caused by: java.lang.NullPointerException: Cannot invoke "org.springframework.cloud.netflix.eureka.CloudEurekaClient.getApplications()" because the return value of "org.springframework.cloud.netflix.eureka.serviceregistry.EurekaRegistration.getEurekaClient()" is null
	at org.springframework.cloud.netflix.eureka.serviceregistry.EurekaServiceRegistry.maybeInitializeClient(EurekaServiceRegistry.java:54) ~[spring-cloud-netflix-eureka-client-4.1.0.jar:4.1.0]
	at org.springframework.cloud.netflix.eureka.serviceregistry.EurekaServiceRegistry.register(EurekaServiceRegistry.java:38) ~[spring-cloud-netflix-eureka-client-4.1.0.jar:4.1.0]
	at org.springframework.cloud.netflix.eureka.serviceregistry.EurekaAutoServiceRegistration.start(EurekaAutoServiceRegistration.java:83) ~[spring-cloud-netflix-eureka-client-4.1.0.jar:4.1.0]
	at org.springframework.context.support.DefaultLifecycleProcessor.doStart(DefaultLifecycleProcessor.java:288) ~[spring-context-6.1.4.jar:6.1.4]
	... 12 common frames omitted

• 명확한 원인은 아니지만,
  • @EnableEurekaClient Spring Cloud Version 2022.0 이상의 경우 사용할 수 없다고 함. ( 되는 예제가 있는 것 같던데.. ㅡㅡㅋ )
  • Runtime or Compile JDK 버전이 상이 해서라는 대답이 꽤 많았음.
  • 나의 경우는
    • implementation 'org.springframework.boot:spring-boot-starter-web'를 추가하니 해결됨.

참고.

https://github.com/eugenp/tutorials/tree/master/spring-cloud-modules
https://velog.io/@rockstar/Spring-Cloud-Eureka-Server-%EC%84%A4%EC%A0%95-%EB%B0%8F-MSA-%ED%86%B5%EC%8B%A0-%EB%B0%A9%EB%B2%95
https://velog.io/@ililil9482/MSA-%EA%B5%AC%EC%84%B1-Discovery-Gateway-Config
https://github.com/Jimoou/springboot-microservices?tab=readme-ov-file