Eureka+Ribbon 出现UnknownHostException，服务名无法识别的问题

Question

spring-cloud小白一枚，今天在学习Eureka+Ribbon做负载均衡的时候，一直出现UnknownHostException错误

网上大部分的回答都集中于说，在

    @LoadBalanced
    @Bean
    RestTemplate restTemplate(){
        return new RestTemplate();
    }

中增加LoadBalanced，但是我写的时候一直是带着LoadBalanced的，一直都没有发现错误，请大神们指教。

父工程的pom.xml

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.0.7.RELEASE</version>
        <relativePath/>
    </parent>

    <groupId>com.hello</groupId>
    <artifactId>0710Chapter03</artifactId>
    <packaging>pom</packaging>
    <version>1.0-SNAPSHOT</version>
    <modules>
        <module>EurekaServer</module>
        <module>EurekaClient</module>
        <module>RibbonConsumer</module>
    </modules>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <java.version>1.8</java.version>
    </properties>

    <dependencies>

        <dependency>
            <groupId>log4j</groupId>
            <artifactId>log4j</artifactId>
            <version>1.2.12</version>
        </dependency>

        <dependency>
            <groupId>com.github.ben-manes.caffeine</groupId>
            <artifactId>caffeine</artifactId>
            <version>2.8.5</version>
        </dependency>

        <dependency>
            <groupId>javax.xml.bind</groupId>
            <artifactId>jaxb-api</artifactId>
            <version>2.3.0-b170201.1204</version>
        </dependency>

        <dependency>
            <groupId>javax.activation</groupId>
            <artifactId>activation</artifactId>
            <version>1.1</version>
        </dependency>

        <dependency>
            <groupId>org.glassfish.jaxb</groupId>
            <artifactId>jaxb-runtime</artifactId>
            <version>2.3.0-b170127.1453</version>
        </dependency>

    </dependencies>

    <dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-dependencies</artifactId>
                <version>Finchley.RELEASE</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
        </dependencies>
    </dependencyManagement>


</project>

消费者的pom.xml

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <parent>
        <artifactId>0710Chapter03</artifactId>
        <groupId>com.hello</groupId>
        <version>1.0-SNAPSHOT</version>
    </parent>
    <modelVersion>4.0.0</modelVersion>

    <artifactId>RibbonConsumer</artifactId>
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-ribbon</artifactId>
            <version>1.3.1.RELEASE</version>
        </dependency>

        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-eureka</artifactId>
            <version>1.3.1.RELEASE</version>
        </dependency>

    </dependencies>

    <dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-dependencies</artifactId>
                <version>Finchley.RELEASE</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
        </dependencies>
    </dependencyManagement>


</project>

启动类

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.loadbalancer.LoadBalanced;
import org.springframework.cloud.netflix.eureka.EnableEurekaClient;
import org.springframework.context.annotation.Bean;
import org.springframework.web.client.RestTemplate;


@EnableEurekaClient
@SpringBootApplication
public class ConsumerApplication {

    @LoadBalanced
    @Bean
    RestTemplate restTemplate(){
        return new RestTemplate();
    }

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

}

controller

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.client.RestTemplate;

@RestController
public class ConsumerController {
    
    @Autowired
    RestTemplate restTemplate;

    @RequestMapping(value = "/ribbon-hello",method = RequestMethod.GET)
    public String helloConsumer(){
        return this.restTemplate.getForObject("http://HELLO-SERVICE/hello",String.class);
    }

}

这个是eureka的运行截图

完整的报错是这个

2020-07-13 16:29:35.765 ERROR 8952 --- [nio-9000-exec-3] o.a.c.c.C.[.[.[/].[dispatcherServlet]    : Servlet.service() for servlet [dispatcherServlet] in context with path [] threw exception [Request processing failed; nested exception is org.springframework.web.client.ResourceAccessException: I/O error on GET request for "http://HELLO-SERVICE/hello": HELLO-SERVICE; nested exception is java.net.UnknownHostException: HELLO-SERVICE] with root cause

java.net.UnknownHostException: HELLO-SERVICE

at java.base/java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:220) ~[na:na]
at java.base/java.net.Socket.connect(Socket.java:591) ~[na:na]
at java.base/java.net.Socket.connect(Socket.java:540) ~[na:na]
at java.base/sun.net.NetworkClient.doConnect(NetworkClient.java:182) ~[na:na]
at java.base/sun.net.www.http.HttpClient.openServer(HttpClient.java:474) ~[na:na]
at java.base/sun.net.www.http.HttpClient.openServer(HttpClient.java:569) ~[na:na]
at java.base/sun.net.www.http.HttpClient.<init>(HttpClient.java:242) ~[na:na]
at java.base/sun.net.www.http.HttpClient.New(HttpClient.java:341) ~[na:na]
at java.base/sun.net.www.http.HttpClient.New(HttpClient.java:362) ~[na:na]
at java.base/sun.net.www.protocol.http.HttpURLConnection.getNewHttpClient(HttpURLConnection.java:1248) ~[na:na]
at java.base/sun.net.www.protocol.http.HttpURLConnection.plainConnect0(HttpURLConnection.java:1187) ~[na:na]
at java.base/sun.net.www.protocol.http.HttpURLConnection.plainConnect(HttpURLConnection.java:1081) ~[na:na]
at java.base/sun.net.www.protocol.http.HttpURLConnection.connect(HttpURLConnection.java:1015) ~[na:na]
at org.springframework.http.client.SimpleBufferingClientHttpRequest.executeInternal(SimpleBufferingClientHttpRequest.java:76) ~[spring-web-5.0.11.RELEASE.jar:5.0.11.RELEASE]
at org.springframework.http.client.AbstractBufferingClientHttpRequest.executeInternal(AbstractBufferingClientHttpRequest.java:48) ~[spring-web-5.0.11.RELEASE.jar:5.0.11.RELEASE]
at org.springframework.http.client.AbstractClientHttpRequest.execute(AbstractClientHttpRequest.java:53) ~[spring-web-5.0.11.RELEASE.jar:5.0.11.RELEASE]
at org.springframework.web.client.RestTemplate.doExecute(RestTemplate.java:687) ~[spring-web-5.0.11.RELEASE.jar:5.0.11.RELEASE]
at org.springframework.web.client.RestTemplate.execute(RestTemplate.java:644) ~[spring-web-5.0.11.RELEASE.jar:5.0.11.RELEASE]
at org.springframework.web.client.RestTemplate.getForObject(RestTemplate.java:296) ~[spring-web-5.0.11.RELEASE.jar:5.0.11.RELEASE]
at com.hello.controller.ConsumerController.helloConsumer(ConsumerController.java:30) ~[classes/:na]
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:na]
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:na]
at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:na]
at java.base/java.lang.reflect.Method.invoke(Method.java:567) ~[na:na]
at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:209) ~[spring-web-5.0.11.RELEASE.jar:5.0.11.RELEASE]
at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:136) ~[spring-web-5.0.11.RELEASE.jar:5.0.11.RELEASE]
at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:102) ~[spring-webmvc-5.0.11.RELEASE.jar:5.0.11.RELEASE]
at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:891) ~[spring-webmvc-5.0.11.RELEASE.jar:5.0.11.RELEASE]
at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:797) ~[spring-webmvc-5.0.11.RELEASE.jar:5.0.11.RELEASE]
at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87) ~[spring-webmvc-5.0.11.RELEASE.jar:5.0.11.RELEASE]
at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:991) ~[spring-webmvc-5.0.11.RELEASE.jar:5.0.11.RELEASE]
at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:925) ~[spring-webmvc-5.0.11.RELEASE.jar:5.0.11.RELEASE]
at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:981) ~[spring-webmvc-5.0.11.RELEASE.jar:5.0.11.RELEASE]
at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:873) ~[spring-webmvc-5.0.11.RELEASE.jar:5.0.11.RELEASE]
at javax.servlet.http.HttpServlet.service(HttpServlet.java:635) ~[tomcat-embed-core-8.5.35.jar:8.5.35]
at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:858) ~[spring-webmvc-5.0.11.RELEASE.jar:5.0.11.RELEASE]
at javax.servlet.http.HttpServlet.service(HttpServlet.java:742) ~[tomcat-embed-core-8.5.35.jar:8.5.35]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231) ~[tomcat-embed-core-8.5.35.jar:8.5.35]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-8.5.35.jar:8.5.35]
at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52) ~[tomcat-embed-websocket-8.5.35.jar:8.5.35]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-8.5.35.jar:8.5.35]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-8.5.35.jar:8.5.35]
at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:99) ~[spring-web-5.0.11.RELEASE.jar:5.0.11.RELEASE]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) ~[spring-web-5.0.11.RELEASE.jar:5.0.11.RELEASE]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-8.5.35.jar:8.5.35]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-8.5.35.jar:8.5.35]
at org.springframework.web.filter.HttpPutFormContentFilter.doFilterInternal(HttpPutFormContentFilter.java:109) ~[spring-web-5.0.11.RELEASE.jar:5.0.11.RELEASE]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) ~[spring-web-5.0.11.RELEASE.jar:5.0.11.RELEASE]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-8.5.35.jar:8.5.35]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-8.5.35.jar:8.5.35]
at org.springframework.web.filter.HiddenHttpMethodFilter.doFilterInternal(HiddenHttpMethodFilter.java:93) ~[spring-web-5.0.11.RELEASE.jar:5.0.11.RELEASE]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) ~[spring-web-5.0.11.RELEASE.jar:5.0.11.RELEASE]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-8.5.35.jar:8.5.35]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-8.5.35.jar:8.5.35]
at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:200) ~[spring-web-5.0.11.RELEASE.jar:5.0.11.RELEASE]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) ~[spring-web-5.0.11.RELEASE.jar:5.0.11.RELEASE]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-8.5.35.jar:8.5.35]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-8.5.35.jar:8.5.35]
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:198) ~[tomcat-embed-core-8.5.35.jar:8.5.35]
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96) ~[tomcat-embed-core-8.5.35.jar:8.5.35]
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:493) ~[tomcat-embed-core-8.5.35.jar:8.5.35]
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:140) ~[tomcat-embed-core-8.5.35.jar:8.5.35]
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:81) ~[tomcat-embed-core-8.5.35.jar:8.5.35]
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:87) ~[tomcat-embed-core-8.5.35.jar:8.5.35]
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:342) ~[tomcat-embed-core-8.5.35.jar:8.5.35]
at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:800) ~[tomcat-embed-core-8.5.35.jar:8.5.35]
at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66) ~[tomcat-embed-core-8.5.35.jar:8.5.35]
at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:806) ~[tomcat-embed-core-8.5.35.jar:8.5.35]
at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1498) ~[tomcat-embed-core-8.5.35.jar:8.5.35]
at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49) ~[tomcat-embed-core-8.5.35.jar:8.5.35]
at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128) ~[na:na]
at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628) ~[na:na]
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) ~[tomcat-embed-core-8.5.35.jar:8.5.35]
at java.base/java.lang.Thread.run(Thread.java:835) ~[na:na]

Answer 1

已经解决了，不过解决的方式很奇怪

我使用的是 Spring Boot 2.0.7.RELEASE 的版本
然后我的Spring Cloud使用的是 Finchley.RELEASE

首先说一下我是如何解决的

把RibbonConsumer的pom.xml中，对于ribbon和eureka的依赖

从

        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-ribbon</artifactId>
            <version>1.3.1.RELEASE</version>
        </dependency>

        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-eureka</artifactId>
            <version>1.3.1.RELEASE</version>
        </dependency>

改成

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

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

---

我的经历是这样的

我的EurekaServer和EurekaClient都是正常运行的，但是唯独RibbonConsumer不可以
经过我的不断测试发现了这个问题：

在使用

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

        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-eureka</artifactId>
            <version>1.3.1.RELEASE</version>
        </dependency>

的时候是正常的

同时，使用

        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
        </dependency>
        
        
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-ribbon</artifactId>
            <version>1.3.1.RELEASE</version>
        </dependency>

的时候也是正常的

最后，使用我刚刚提到的

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

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

也是正常的

但就是使用

        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-ribbon</artifactId>
            <version>1.3.1.RELEASE</version>
        </dependency>

        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-eureka</artifactId>
            <version>1.3.1.RELEASE</version>
        </dependency>

的时候不正常

会出现UnknownHostException错误

---

背景：
最近在使用翟永超老师的《Spring Cloud微服务实战》这本书学习Spring Cloud

因为这本书的出版时间是2017年，所以用的Spring Boot和Spring Cloud的版本比较老了，自己升级了一下版本

我用的是Spring Boot 2.0.7.RELEASE 的版本，Spring Cloud使用的Finchley.RELEASE
前面也出现了很多版本不兼容的问题，但基本上都是替换成Netflix版本的就可以了。

唯独在这个Ribbon的地方卡了很久都没解决，因为没有替换成Netflix的版本，然后自己又是严格按照书上写的，感觉不会出问题，而没想到的是就是这里出了问题。

另外就是这个报错报的也很奇怪，没有直接报版本错误，而是运行时报错，就特别难找到原因。

希望大家能有所启发