服务发现中的 eureka unknownHostException

Question

我有两个微服务，

eureka-client-1 运行在 localhost:8081
eureka-client-2 运行在 localhost:8082

这两个都是在 localhost:8761 运行 '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。而不是调用 http://localhost:8082, i want to call http://eureka-client-2 但这会在 Eureka 服务发现期间抛出 java.net.UnknownHostException。

经过搜索，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？

求推荐。

@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>

application.properties 对于客户端 1，对于客户端 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

application.properties 对于尤里卡服务器

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

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

首先，我要搬家：

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

配置 class。

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 class 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

的已注册服务的键

我写了关于 Microservices Registration and Discovery using Spring Cloud Eureka, Ribbon and Feign 的博客，其中还包括发现服务器的源代码以及使用 Jersey 1 和 Spring MVC 开发的两个客户端。

Answer 2

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 实例 = 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";
    }
}

Answer 3

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

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

Answer 4

解决方法是你错过了@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();
  }

如果你只使用spring，我建议你new RestTemplate()

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

服务发现中的 eureka unknownHostException

eureka unknownHostException in service discovery

java

spring

service-discovery

spring-boot

netflix-eureka