一,问题

采取eureka集群、客户端通过Ribbon调用服务,Ribbon端报下列异常

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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: IT虾米网
 
com.netfix.discovery.shared.taransport.TransportException: Cannot execute request on any known server

Spring Cloud版本比较乱,版本关联引用更是乱,最终我切换到 <spring-cloud.version> Greenwich.SR1 </spring-cloud.version> 异常为: No instances available for SERVICE-HI

二、寻找答案 

网上答案千奇百怪

1,Spring Cloud 官网,RestTemplate bean配置中添加负载均衡注解@LoadBalanced,我添加了

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

结果无效仍然一样报错

2,访问的服务名名称不能有下划线:

我的名称是“SERVICE-HI”本身就不存在下划线,所以不考虑这条。

3,主机名称没在系统文件hosts中配置,ping不通你服务名:

很扯的答案,为什么要配host,负载多台机器让主机名指向谁?不考虑此答案

三,分析问题

百度不到,自己分析原因,发现ribbon服务器没有注册到 eureka server中

分析原理:我的客户端服务“SERVICE-HI”已经成功注册到eureka server中了,如果ribbon服务器不在eureka server中注册,是不会知道客户端服务“SERVICE-HI”的存在以及它存在的位置,那么结论就是,因为ribbon服务器没有在eureka server中注册成功,所以不能识别主机名称。

四,解决问题

配置文件

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eureka:
  client:
   serviceUrl:
    defaultZone: IT虾米网
server:
  port: 8764
spring:
  application:
   name: service-ribbon

依赖导入

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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 >

主程序注释

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

有问题,最终发现@EnableDiscoveryClient标签无法注册到注册中心,百度@EnableDiscoveryClient,得到的结论是

@EnableDiscoveryClient和@EnableEurekaClient一样,能够让注册中心能够发现,扫描到改服务,不同点:@EnableEurekaClient只适用于Eureka作为注册中心,@EnableDiscoveryClient 可以是Eureka或其他(consul、zookeeper等)注册中心 。

具体原因不去分析,这里先直接切换为@EnableEurekaClient注释

@EnableEurekaClient在哪个包里简直是迷一样的存在,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 >

修改主程序注释

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

这里提一句在 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 >

重新启动ribbon,发现控制台输入

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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

浏览器测试访问成功!!!

五,附件:Greenwich.SR1 版中常用依赖

有好多问题都是因为 不同版本中引入不正确的依赖导致,这里列出 Greenwich.SR1 版中常用依赖,这里都不需要指定版本号

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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 >

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


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