RestTemplate or discoveryClient - which one to use in Spring Cloud application? - spring-boot

Question

I am borrowing the below the code from Spring blog here.
#SpringBootApplication
#EnableEurekaClient
#EnableFeignClients
public class Application {
public static void main(String[] args) {
new SpringApplicationBuilder(Application.class)
.web(false)
.run(args);
}
}
#Component
class DiscoveryClientExample implements CommandLineRunner {
#Autowired
private DiscoveryClient discoveryClient;
#Override
public void run(String... strings) throws Exception {
discoveryClient.getInstances("photo-service").forEach((ServiceInstance s) -> {
System.out.println(ToStringBuilder.reflectionToString(s));
});
discoveryClient.getInstances("bookmark-service").forEach((ServiceInstance s) -> {
System.out.println(ToStringBuilder.reflectionToString(s));
});
}
}
#Component
class RestTemplateExample implements CommandLineRunner {
#Autowired
private RestTemplate restTemplate;
#Override
public void run(String... strings) throws Exception {
// use the "smart" Eureka-aware RestTemplate
ResponseEntity<List<Bookmark>> exchange =
this.restTemplate.exchange(
"http://bookmark-service/{userId}/bookmarks",
HttpMethod.GET,
null,
new ParameterizedTypeReference<List<Bookmark>>() {
},
(Object) "mstine");
exchange.getBody().forEach(System.out::println);
}
}
There are two options of consuming microservice endpoints from other microservices.
RestTemplate - provides load balancing feature, which load balances the request. But if I have a service running in 3 nodes, does RestTemplate knows if one node is down or responding and "intelligently" load balance between just two of it.
Using DiscoveryClient to get a service instance and make request (as demonstrated above). In this case, though not load balanced, I think the service instance returned is responsive.
The latter loses load balancing feature but provides an active service instance
The former load balances but the resultant instance may be inactive.
I am wondering to which is the preferred one to use?
Please correct me if my understanding above is incorrect.

Answer 1

The first option of using resttemplate is a better option
We just need to annotate the resttemplate with
#LoadBalanced and have a zuul proxy server as the edge server. If we do that then any request to the edge server will be load balanced by default with ribbon and the resttemplate will route the request in a round robin fashion.
If we use a Discoverclient then we cannot route teh request across various instances.