服务发现中的 eureka unknownHostException

Question

我有两个微服务，

1. 在 localhost:8081 上运行的 eureka-client-1
2. 在 localhost:8082 上运行的 eureka-client-2

这两个都是在 localhost:8761 上运行的“eureka-server”注册的 DiscoveryClients。

在下面的代码片段中，我试图从 eureka-client-1 调用 eureka-client-2。 我想调用http://eureka-client-2而不是调用http://localhost:8082 ，但这会在 Eureka 服务发现期间抛出 java.net.UnknownHostException 。

搜索后，我发现我需要使用“Brixton”来完成它。

有没有办法用 Camden.SR3 做到这一点？

请建议。

@Component
public class HystrixDemoService {   

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

    @HystrixCommand(fallbackMethod = "getFallbackCustomerName")
    public String getCustomerName() {
        RestTemplate restTemplate = new RestTemplate();
        URI uri = URI.create("http://eureka-client-2");     // fails here
        return restTemplate.getForObject(uri, String.class);
    }

    public String getFallbackCustomerName() {
        System.out.println("coming inside fallback method");
        return "Resillient Customer";
    }
}

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>

    <groupId>com.example</groupId>
    <artifactId>demo-pranay-eureka-client1</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <packaging>jar</packaging>

    <name>demo-pranay-eureka-client1</name>
    <description>Demo project for Spring Boot</description>

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>1.4.2.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>

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

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-actuator</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-eureka</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-hystrix</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>

    <dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-dependencies</artifactId>
                <version>Camden.SR3</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
        </dependencies>
    </dependencyManagement>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>


</project>

客户端 1 的 application.properties，客户端 2 类似（只是更改名称，即 eureka-client-2）

spring.application.name=eureka-client-1
server.port=8081
eureka:
  client:
    registerWithEureka: true
    serviceUrl:
      defaultZone: http://localhost:8761/eureka/
  instance:
    leaseRenewalIntervalInSeconds: 10
    statusPageUrlPath: /info
    healthCheckUrlPath: /health

尤里卡服务器的application.properties

spring.application.name=eureka-service
server.port=8761
eureka:
  client:
    registerWithEureka: false
    serviceUrl:
      defaultZone: http://localhost:8761/eureka/
  instance:
    leaseRenewalIntervalInSeconds: 10
    statusPageUrlPath: /info
    healthCheckUrlPath: /health

Answer 1

对我来说，解决这个问题唯一需要做的就是将 spring 注释 @LoadBalanced 添加到

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

Answer 2

解决方案是您错过了@LoadBalanced 。
如果您使用 Spring Boot 或 Sprint Cloud，我更喜欢使用RestTemplateBuilder builder

  @Bean
  @LoadBalanced
  public RestTemplate restTemplate(RestTemplateBuilder builder) {
    return builder.build();
  }

如果您只使用 spring，我建议您使用new RestTemplate()

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

Answer 3

如前所述，我相信您可能缺少eureka-client-1 Ribbon配置。

首先，我会移动：

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

到一个配置类。

将Ribbon配置添加到application.yml ，例如：

the-eureka-client-2:
   ribbon:
     # Eureka vipAddress of the target service
     DeploymentContextBasedVipAddresses: eureka-client-2

     #listOfServers: localhost:${SERVER.PORT}
     NIWSServerListClassName: com.netflix.niws.loadbalancer.DiscoveryEnabledNIWSServerList

     # Interval to refresh the server list from the source (ms)
     ServerListRefreshInterval: 30000

在HystrixDemoService类中注入restTemplate而不是为每个请求实例化一个新的。 RestTemplate 是线程安全的：

@Component
public class HystrixDemoService {   

    @Autowired
    public RestTemplate restTemplate;
...
    @HystrixCommand(fallbackMethod = "getFallbackCustomerName")
    public String getCustomerName() {
      URI uri = URI.create("http://eureka-client-2");
      return this.restTemplate.getForObject(uri, String.class);
    }

其中the-eureka-client-2是映射到名称为： eureka-client-2的注册服务的键

我写了一篇关于使用 Spring Cloud Eureka、Ribbon 和 Feign 进行微服务注册和发现的博客，其中还包括发现服务器的源代码和两个使用Jersey 1和Spring MVC开发的客户端。

Answer 4

以下更改对我有用。

@SpringBootApplication
public class DemoPranayEurekaClient1Application {
    public static void main(String[] args) {
        SpringApplication.run(DemoPranayEurekaClient1Application.class, args);
    }
}

@EnableDiscoveryClient
@EnableCircuitBreaker
@RestController
class HystrixDemoApplication {
    @Autowired
    HystrixDemoService hystrixDemoService;

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

    @RequestMapping("/")
    public String name() {
        String str = hystrixDemoService.getCustomerName();
        return "I'm A talking to "+str;
    }

}

下面是用于选择 eureka-client-2 实例的代码行...

ServiceInstance instance = loadBalancer.choose("eureka-client-2");

@Component
public class HystrixDemoService {

    @Autowired
    private LoadBalancerClient loadBalancer;

    @HystrixCommand(fallbackMethod = "getFallbackCustomerName")
    public String getCustomerName() {
        RestTemplate restTemplate = new RestTemplate();
        ServiceInstance instance = loadBalancer.choose("eureka-client-2");
        URI uri = instance.getUri();
        return restTemplate.getForObject(uri, String.class);
    }

    public String getFallbackCustomerName() {
        System.out.println("coming inside fallback method");
        return "Resillient Customer";
    }
}