eureka中顯示有服務但是通過ribbon調用顯示No instances available for service-hello的問題

一，問題

采取eureka集群、客戶端通過Ribbon調用服務，Ribbon端報下列異常

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java.net.UnknownHostException: SERVICE-HI   java.lang.IllegalStateException: No instances available for SERVICE-HI   java.lang.IllegalStateException: Request URI does not contain a valid hostname: http://SERVICE-HI   com.netfix.discovery.shared.taransport.TransportException: Cannot execute request on any known server

Spring Cloud版本比較亂，版本關聯引用更是亂，最終我切換到 <spring-cloud.version> Greenwich.SR1 </spring-cloud.version> 異常為： No instances available for SERVICE-HI

二、尋找答案 

網上答案千奇百怪

1，Spring Cloud 官網，RestTemplate bean配置中添加負載均衡注解@LoadBalanced，我添加了

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@Bean @LoadBalanced public RestTemplate getRestTemplate(){    return new RestTemplate(); }

結果無效仍然一樣報錯

2，訪問的服務名名稱不能有下划線：

我的名稱是“SERVICE-HI”本身就不存在下划線，所以不考慮這條。

3，主機名稱沒在系統文件hosts中配置，ping不通你服務名：

很扯的答案，為什么要配host，負載多台機器讓主機名指向誰？不考慮此答案

三，分析問題

百度不到，自己分析原因，發現ribbon服務器沒有注冊到 eureka server中

分析原理：我的客戶端服務“SERVICE-HI”已經成功注冊到eureka server中了，如果ribbon服務器不在eureka server中注冊，是不會知道客戶端服務“SERVICE-HI”的存在以及它存在的位置，那么結論就是，因為ribbon服務器沒有在eureka server中注冊成功，所以不能識別主機名稱。

四，解決問題

配置文件

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eureka:   client:    serviceUrl:     defaultZone: http://localhost:8761/eureka/ server:   port: 8764 spring:   application:    name: service-ribbon

依賴導入

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< dependencies >    < dependency >      < groupId >org.springframework.boot</ groupId >      < artifactId >spring-boot-starter-web</ artifactId >    </ dependency >    < dependency >      < groupId >org.springframework.cloud</ groupId >      < artifactId >spring-cloud-starter-netflix-ribbon</ artifactId >    </ dependency > </ dependencies >

主程序注釋

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

有問題，最終發現@EnableDiscoveryClient標簽無法注冊到注冊中心，百度@EnableDiscoveryClient，得到的結論是

@EnableDiscoveryClient和@EnableEurekaClient一樣，能夠讓注冊中心能夠發現，掃描到改服務，不同點：@EnableEurekaClient只適用於Eureka作為注冊中心，@EnableDiscoveryClient 可以是Eureka或其他（consul、zookeeper等）注冊中心 。

具體原因不去分析，這里先直接切換為@EnableEurekaClient注釋

@EnableEurekaClient在哪個包里簡直是迷一樣的存在，不同版本的spring cloud 中位置不同，我使用Greenwich.SR1，需要引入下面的包

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< dependency >    < groupId >org.springframework.cloud</ groupId >    < artifactId >spring-cloud-starter-netflix-eureka-client</ artifactId > </ dependency >

修改主程序注釋

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import org.springframework.cloud.netflix.eureka.EnableEurekaClient; import org.springframework.cloud.netflix.hystrix.EnableHystrix;     @SpringBootApplication @EnableEurekaClient @EnableHystrix //我開啟了段容器 public class ServiceRibbonApplication {      public static void main(String[] args) {      SpringApplication.run( ServiceRibbonApplication. class , args );    }   }

這里提一句在 Greenwich.SR1中段容器在下面包中

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< dependency >    < groupId >org.springframework.cloud</ groupId >    < artifactId >spring-cloud-starter-netflix-hystrix</ artifactId > </ dependency >

重新啟動ribbon，發現控制台輸入

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2019-06-15 13:08:06.668 INFO 14796 --- [      main] com.netflix.discovery.DiscoveryClient  : Getting all instance registry info from the eureka server 2019-06-15 13:08:06.878 INFO 14796 --- [      main] com.netflix.discovery.DiscoveryClient  : The response status is 200 2019-06-15 13:08:06.882 INFO 14796 --- [      main] com.netflix.discovery.DiscoveryClient  : Starting heartbeat executor: renew interval is: 30 2019-06-15 13:08:06.886 INFO 14796 --- [      main] c.n.discovery.InstanceInfoReplicator   : InstanceInfoReplicator onDemand update allowed rate per min is 4 2019-06-15 13:08:06.891 INFO 14796 --- [      main] com.netflix.discovery.DiscoveryClient  : Discovery Client initialized at timestamp 1560575286889 with initial instances count: 2 2019-06-15 13:08:06.894 INFO 14796 --- [      main] o.s.c.n.e.s.EurekaServiceRegistry    : Registering application SERVICE-RIBBON with eureka with status UP 2019-06-15 13:08:06.896 INFO 14796 --- [      main] com.netflix.discovery.DiscoveryClient  : Saw local status change event StatusChangeEvent [timestamp=1560575286896, current=UP, previous=STARTING] 2019-06-15 13:08:06.900 INFO 14796 --- [nfoReplicator-0] com.netflix.discovery.DiscoveryClient  : DiscoveryClient_SERVICE-RIBBON/DESKTOP-FJQITE3:service-ribbon:8764: registering service... 2019-06-15 13:08:06.958 INFO 14796 --- [nfoReplicator-0] com.netflix.discovery.DiscoveryClient  : DiscoveryClient_SERVICE-RIBBON/DESKTOP-FJQITE3:service-ribbon:8764 - registration status: 204 2019-06-15 13:08:06.961 INFO 14796 --- [      main] o.s.b.w.embedded.tomcat.TomcatWebServer : Tomcat started on port(s): 8764 (http) with context path '' 2019-06-15 13:08:06.963 INFO 14796 --- [      main] .s.c.n.e.s.EurekaAutoServiceRegistration : Updating port to 8764 2019-06-15 13:08:06.967 INFO 14796 --- [      main] cn.meylink.ServiceRibbonApplication   : Started ServiceRibbonApplication in 5.868 seconds (JVM running for 7.204)

查看Eureka

瀏覽器測試訪問成功！！！

五，附件：Greenwich.SR1 版中常用依賴

有好多問題都是因為 不同版本中引入不正確的依賴導致，這里列出 Greenwich.SR1 版中常用依賴，這里都不需要指定版本號

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< dependencies >    <!-- eureka client -->    < dependency >      < groupId >org.springframework.cloud</ groupId >      < artifactId >spring-cloud-starter-netflix-eureka-client</ artifactId >    </ dependency >    <!-- eureka server -->    < dependency >      < groupId >org.springframework.cloud</ groupId >      < artifactId >spring-cloud-starter-netflix-eureka-server</ artifactId >    </ dependency >    <!-- 段容器 -->    < dependency >      < groupId >org.springframework.cloud</ groupId >      < artifactId >spring-cloud-starter-netflix-hystrix</ artifactId >    </ dependency >    <!-- ribbon -->    < dependency >      < groupId >org.springframework.cloud</ groupId >      < artifactId >spring-cloud-starter-netflix-ribbon</ artifactId >    </ dependency >    <!-- feign -->    < dependency >      < groupId >org.springframework.cloud</ groupId >      < artifactId >spring-cloud-starter-openfeign</ artifactId >    </ dependency >    <!-- config server -->    < dependency >      < groupId >org.springframework.cloud</ groupId >      < artifactId >spring-cloud-config-server</ artifactId >    </ dependency >    <!-- config client -->    < dependency >      < groupId >org.springframework.cloud</ groupId >      < artifactId >spring-cloud-starter-config</ artifactId >    </ dependency >    <!-- zuul -->    < dependency >      < groupId >org.springframework.cloud</ groupId >      < artifactId >spring-cloud-starter-netflix-zuul</ artifactId >    </ dependency >    < dependency >      < groupId >org.springframework.boot</ groupId >      < artifactId >spring-boot-starter-test</ artifactId >      < scope >test</ scope >    </ dependency > </ dependencies >

轉自https://www.jb51.net/article/163154.htm