SpringBoot: LoadBalancer [server]: Error choosing server for key default - spring-boot

Question

I'm creating a load balance feature on my project in which I have three server that will simultaneously ping for 15 seconds. However, when I already run my client-side, it always goes to the fallback page and received an error of "LoadBalancer [server]: Error choosing server for key default" even if the servers are already running.
Here are the codes in my project:
app.properties
server.port=8788
server.ribbon.eureka.enabled=false
server.ribbon.listOfServers=localhost:8787,localhost:8789,localhost:8790
#every 15 seconds
server.ribbon.ServerListRefreshInterval=15000
client service (wherein it is my fallback method)
private LoadBalancerClient loadBalancer;
private RestTemplate restTemplate;
public ClientService(RestTemplate rest) {
this.restTemplate = rest;
}
#HystrixCommand(fallbackMethod = "reliable")
public String login() {
ServiceInstance instance = loadBalancer.choose("server");
URI uri = URI.create(String.format("http://%s:%s/admin/ping", instance.getHost(), instance.getPort()));
//URI uri = URI.create("http://localhost:8787/admin/ping");
return this.restTemplate.getForObject(uri, String.class);
}
MainController
public class MainController{
private final static Logger LOGGER = LoggerFactory.getLogger(MainController.class);
#Autowired
private ClientService clientService;
#LoadBalanced
#Bean
public RestTemplate rest(RestTemplateBuilder builder) {
return builder.build();
}
#Autowired
RestTemplate restTemplate;
...
Client client = new Client();
WebResource resource = client.resource("http://%s:%s/auth/loginvalidate");
ClientResponse response = resource.type(MediaType.APPLICATION_JSON)
.header("Authorization", "Basic " + encodePw)
.get(ClientResponse.class);

Answer 1

I got rid of that error by doing two things:
1) Add the following properties to the remote service:
management.endpoints.web.exposure.include: "*"
management.endpoint.health.enabled: "true"
management.endpoint.restart.enabled: "true"
management.endpoint.info.enabled: "true"
2) Make sure that there is a ping endpoint in the remote service:
public class MainController{
#RequestMapping("/")
public String ribbonPing() {
return this.hostName;
}
}
I added a few amendments to the example provided by Kubernetes Circuit Breaker & Load Balancer Example to test this scenario and put in here.
I suggest that you follow those links as a kind of "best practises" guide in order to build your Hystrix/Ribbon solution. Pay special attention to:
the starters/dependencies added to the pom files
the structure of the Java classes (how and where each bean is declared and injected)
how you configure your (micro-)services (in this case with K8s ConfigMaps)