【Java】建立Eureka集群因配置defaultZone时使用localhost导致失败

• Z时代
• 2024-01-10
• 分类：技术分享

server:
port: 8081
spring:
application:
name: eureka-ser1
eureka:
instance:
hostname: localhost
client:
serviceUrl:
defaultZone: http://localhost:8082/eureka/
fetch-registry: true
register-with-eureka: true

server:
port: 8082
spring:
application:
name: eureka-ser2
eureka:
instance:
hostname: localhost
client:
serviceUrl:
defaultZone: http://localhost:8081/eureka/
fetch-registry: true
register-with-eureka: true

public boolean isThisMyUrl(String url) {
String myUrlConfigured = this.serverConfig.getMyUrl();
return myUrlConfigured != null ? myUrlConfigured.equals(url) : this.isInstanceURL(url, this.applicationInfoManager.getInfo());
}
public boolean isInstanceURL(String url, InstanceInfo instance) {
String hostName = hostFromUrl(url);
String myInfoComparator = instance.getHostName();
if (this.clientConfig.getTransportConfig().applicationsResolverUseIp()) {
myInfoComparator = instance.getIPAddr();
}
return hostName != null && hostName.equals(myInfoComparator);
}

eureka:
instance:
hostname: ser1

eureka:
instance:
hostname: ser2

2021-01-31 20:28:12.251  INFO 1828 --- [           main] c.n.eureka.cluster.PeerEurekaNodes       : Adding new peer nodes [http://localhost:8081/eureka/]
2021-01-31 20:28:12.280  INFO 1828 --- [           main] c.n.d.provider.DiscoveryJerseyProvider   : Using JSON encoding codec LegacyJacksonJson
2021-01-31 20:28:12.281  INFO 1828 --- [           main] c.n.d.provider.DiscoveryJerseyProvider   : Using JSON decoding codec LegacyJacksonJson
2021-01-31 20:28:12.282  INFO 1828 --- [           main] c.n.d.provider.DiscoveryJerseyProvider   : Using XML encoding codec XStreamXml
2021-01-31 20:28:12.282  INFO 1828 --- [           main] c.n.d.provider.DiscoveryJerseyProvider   : Using XML decoding codec XStreamXml
2021-01-31 20:28:12.478  INFO 1828 --- [           main] c.n.eureka.cluster.PeerEurekaNodes       : Replica node URL:  http://localhost:8081/eureka/

server:
port: 8890
spring:
application:
name: eureka-cli
eureka:
client:
register-with-eureka: true
fetch-registry: true
service-url:
defaultZone: http://localhost:8081/eureka/,http://localhost:8082/eureka/

Eureka在实际使用过程中，基本上都是使用集群的方式。在本地测试Eureka集群搭建过程中遇到集群不生效的问题，过程如下：

1.搭建2个节点的注册中心

给eureka-server模块添加中心1对应的配置文件application-ser1.yml

server:
port: 8081
spring:
application:
name: eureka-ser1
eureka:
instance:
hostname: localhost
client:
serviceUrl:
defaultZone: http://localhost:8082/eureka/
fetch-registry: true
register-with-eureka: true

给eureka-server模块添加中心2对应的配置文件application-ser2.yml

server:
port: 8082
spring:
application:
name: eureka-ser2
eureka:
instance:
hostname: localhost
client:
serviceUrl:
defaultZone: http://localhost:8081/eureka/
fetch-registry: true
register-with-eureka: true

通过2个注册中心相互注册，搭建了双节点集群。

2.启动注册中心集群

登录http://localhost:8081/查看中心1界面：

登录http://localhost:8082/查看中心2界面：

从注册中心界面可以看出集群没有生效，服务没有共享。
查看日志找到以下内容：
2021-01-31 19:06:44.285 WARN 316 --- [ main] c.n.eureka.cluster.PeerEurekaNodes : The replica size seems to be empty. Check the route 53 DNS Registry
注册中心找不到复制节点，所以集群建立失败。

3.集群建立失败原因分析

在eureka源码com.netflix.eureka.cluster.PeerEurekaNodes找到问题原因，该类为eureka集群节点相关类，

public boolean isThisMyUrl(String url) {
String myUrlConfigured = this.serverConfig.getMyUrl();
return myUrlConfigured != null ? myUrlConfigured.equals(url) : this.isInstanceURL(url, this.applicationInfoManager.getInfo());
}
public boolean isInstanceURL(String url, InstanceInfo instance) {
String hostName = hostFromUrl(url);
String myInfoComparator = instance.getHostName();
if (this.clientConfig.getTransportConfig().applicationsResolverUseIp()) {
myInfoComparator = instance.getIPAddr();
}
return hostName != null && hostName.equals(myInfoComparator);
}

这两个方法会把满足hostName.equals(myInfoComparator)这个条件的集群节点删除掉，即配置文件中的eureka.instance.hostname与eureka.client.serviceUrl.defaultZone中服务器主机名，因为上文中配置的都是localhost，所以集群节点都被删除，导致集群找不到节点。

4.修改eureka.instance.hostname重启服务

application-ser1.yml修改为：

eureka:
instance:
hostname: ser1

application-ser2.yml修改为：

eureka:
instance:
hostname: ser2

重新启动，查看注册中心1与2界面如下图：

查看日志，也可找到集群建立日志：

2021-01-31 20:28:12.251  INFO 1828 --- [           main] c.n.eureka.cluster.PeerEurekaNodes       : Adding new peer nodes [http://localhost:8081/eureka/]
2021-01-31 20:28:12.280  INFO 1828 --- [           main] c.n.d.provider.DiscoveryJerseyProvider   : Using JSON encoding codec LegacyJacksonJson
2021-01-31 20:28:12.281  INFO 1828 --- [           main] c.n.d.provider.DiscoveryJerseyProvider   : Using JSON decoding codec LegacyJacksonJson
2021-01-31 20:28:12.282  INFO 1828 --- [           main] c.n.d.provider.DiscoveryJerseyProvider   : Using XML encoding codec XStreamXml
2021-01-31 20:28:12.282  INFO 1828 --- [           main] c.n.d.provider.DiscoveryJerseyProvider   : Using XML decoding codec XStreamXml
2021-01-31 20:28:12.478  INFO 1828 --- [           main] c.n.eureka.cluster.PeerEurekaNodes       : Replica node URL:  http://localhost:8081/eureka/

5.启动客户端进行验证

application.yml配置：

server:
port: 8890
spring:
application:
name: eureka-cli
eureka:
client:
register-with-eureka: true
fetch-registry: true
service-url:
defaultZone: http://localhost:8081/eureka/,http://localhost:8082/eureka/

启动后查看注册中心1和2界面如下：

大工告成，成功建立了eureka集群，完美解决问题。

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