Configuring RoundRobinLoadBalancer for unit tests

Question

Since Ribbon client side load balancer is in maintenance mode, I migrated to RoundRobinLoadBalancer by setting spring.cloud.loadbalancer.ribbon.enabled to false. With Ribbon for client tests I used to do

@Configuration
@Profile("test")
public class ClientTestConfig {
  @Bean
  public StubServer stubServer() {
      return new StubServer().run();
  }

  @Bean
  public ServerList<Server> ribbonServerList() {
      return new StaticServerList<>(new Server("localhost", stubServer().getPort()));
  }
}

Whats the equivalent the code above for RoundRobinLoadBalancer?

Answer 1

I recently did the same switch away from Ribbon. One of the Spring guides has an example of how to configure a custom ServiceInstanceListSupplier: https://spring.io/guides/gs/spring-cloud-loadbalancer/#_load_balance_across_server_instances

For your case this would probably look something like this:

@Configuration
@Profile("test")
public class ClientTestConfig {
  @Bean
  public StubServer stubServer() {
      return new StubServer().run();
  }

  @Bean
  ServiceInstanceListSupplier serviceInstanceListSupplier() {
    return new MyServiceInstanceListSupplier(stubServer().getPort());
  }
}

class MyServiceInstanceListSupplier implements ServiceInstanceListSupplier {

  private final Integer port;

  MyServiceInstanceListSupplier(Integer port) {
    this.port = port;
  }

  @Override
  public String getServiceId() {
    return "";
  }

  @Override
  public Flux<List<ServiceInstance>> get() {
    return Flux.just(Arrays.asList(new DefaultServiceInstance("", "", "localhost", port, false)));
  }
}

Notice that I am using empty strings as the instanceId and serviceId. That is probably not the best practice, but works fine in my case.