Microservices - RestTemplate UnknownHostException

问题

I have a simple setup with a Eureka service registration server, a service for the public API and a service that gets called from the public API using RestTemplate. Eureka tells me that the services are successfully registered, but when I call the service

@Service
public class MyServiceService {

    @Autowired
    private RestTemplate restTemplate;

    private final String serviceUrl;

    public MyServiceService() {
        this.serviceUrl = "http://MY-SERVICE";
    }

    public Map<String, String> getTest() {

        Map<String, String> vars = new HashMap<>();
        vars.put("id", "1");

        restTemplate.setRequestFactory(new HttpComponentsClientHttpRequestFactory());

        return restTemplate.postForObject(serviceUrl+"/test", "", Map.class, vars);
    }
}

I get the following exception

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 POST request for "http://MY-SERVICE/test": MY-SERVICE;
  nested exception is java.net.UnknownHostException: MY-SERVICE] with root cause java.net.UnknownHostException: MY-SERVICE

I created a sample project to illustrate my setup, maybe someone could take a look at it and tell me what's wrong with my setup.

https://github.com/KenavR/spring-boot-microservices-example

thanks

回答1:

As suggested by patrick-grimard switching to Brixton and changing the code were needed fixed the issues. Working Solution is on Github.

Also changed the posted id from request param to request body, which also changed the way I add it to the request.

Service endpoint

@RequestMapping(method = RequestMethod.POST, produces = "application/json; charset=utf-8")
public @ResponseBody Map<String, String> getTest(@RequestBody Map<String, Long> params) {

    Map<String, String> response = new HashMap<>();

    response.put("name", "My Service");

    return response;
}

RestTemplate creation

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

Calling service

@Service
public class MyServiceService {

    @Autowired
    private RestTemplate restTemplate;

    private final String serviceUrl;

    public MyServiceService() {
        this.serviceUrl = "http://my-service";
    }

    public Map<String, String> getTest() {

        Map<String, Long> vars = new HashMap<>();
        vars.put("id", 1L);

        return restTemplate.postForObject(serviceUrl+"/test", vars, Map.class);
    }
}

回答2:

Just for anyone in the future that might also happen to come across this issue, i had the exact same stacktrace, but was slightly different for a solution.

My issue was not related to a configuration from a coding standpoint. It was related to the server i was running the code on. I was ignoring the fact that it was on a DMZ, which doesn't have a DNS, so you have to manually map a domain to an IP.

More or less, make sure your DNS is properly configured on your server, because, from a restTemplate standpoint, it will throw this exact stacktrace.

来源：https://stackoverflow.com/questions/37159662/microservices-resttemplate-unknownhostexception

标签

java

spring-boot

spring-cloud

microservices

netflix-eureka