Ribbon with Spring Cloud and Eureka java.lang.IllegalStateException: No instances available for localhost

问题

I am using

<dependency>
  <groupId>org.springframework.cloud</groupId>
  <artifactId>spring-cloud-netflix</artifactId>
  <version>1.2.3.RELEASE</version>
  <type>pom</type>
  <scope>import</scope>
</dependency>

My main class:

@SpringBootApplication
//@Configuration
@ComponentScan(basePackages = "com.mypackage")
@EnableAutoConfiguration
@EnableEurekaClient
@EnableSwagger2
public class App 
{
  public static void main( String[] args )
  {

    SpringApplication.run(App.class, args);
  }

  @LoadBalanced
  @Bean(name="template")
  RestTemplate restTemplate() {
    return new RestTemplate();
  }
}

My service calling:

@Autowired
private RestTemplate template;

ResponseEntity<String> avs = template.exchange("http://localhost:7075/xyz/json/authenticate",HttpMethod.POST ,request,String.class);

It is throwing the following exception

java.lang.IllegalStateException: No instances available for localhost
    at org.springframework.cloud.netflix.ribbon.RibbonLoadBalancerClient.execute(RibbonLoadBalancerClient.java:90)
    at org.springframework.cloud.client.loadbalancer.RetryLoadBalancerInterceptor$1.doWithRetry(RetryLoadBalancerInterceptor.java:60)
    at org.springframework.cloud.client.loadbalancer.RetryLoadBalancerInterceptor$1.doWithRetry(RetryLoadBalancerInterceptor.java:48)
    at org.springframework.retry.support.RetryTemplate.doExecute(RetryTemplate.java:276)
    at org.springframework.retry.support.RetryTemplate.execute(RetryTemplate.java:157)

回答1:

When you use a @LoadBalanced RestTemplate the hostname needs to be a serviceId not an actual hostname. In your case, it's trying to find a eureka record for localhost and can't find one. See the documentation for how to use multiple RestTemplate objects, one load balanced, one not.

@Configuration
public class MyConfiguration {

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

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

public class MyClass {
    @Autowired
    private RestTemplate restTemplate;

    @Autowired
    @LoadBalanced
    private RestTemplate loadBalanced;

    public String doOtherStuff() {
        return loadBalanced.getForObject("http://stores/stores", String.class);
    }

    public String doStuff() {
        return restTemplate.getForObject("http://example.com", String.class);
    }
}

回答2:

From what I read there is some kind of problem when you try to Autowire RestTemplate while using this Netflix cloud. However I found a workaround. First declare a new @Component class and in it create a method that returns RestTemplate:

@Component
public class RestTemplateComponentFix{

 @Autowired
 SomeConfigurationYouNeed someConfiguration;

 @LoadBalanced
 public RestTemplate getRestTemplate() {
       // TODO set up your restTemplate
        rt.setRequestFactory( new HttpComponentsClientHttpRequestFactory() );
        return rt;
    }

}

After that just Autowire the restTemplateComponentFix in your class and when when you need the rest template call the restTemplate() method. Something like this:

@Service
public class someClass{

    @Autowired
    RestTemplateComponentFix restTemplateComponentFix;

    public void methodUsingRestTemplate(){
        // Some code...
        RestTemplate rt = restTemplateComponentFix.getRestTemplate();
        // Some code...
    }
}

The cool part is that you can easily unit test this code with something like:

RestTemplate rt = Mockito.mock(RestTemplate.class) 
when(restTemplateComponentFix.getRestTemplate()).thenReturn(rt);
when(rt.someMethod()).thenReturn(something);

来源：https://stackoverflow.com/questions/41569558/ribbon-with-spring-cloud-and-eureka-java-lang-illegalstateexception-no-instance

标签

spring-cloud

spring-cloud-netflix

netflix-ribbon