Integrate Spring Cloud load balancing with KeycloakRestTemplate

Question

I have a microservice landscape configured with Spring Cloud discovery so I'm able to access other service instances just using their id's:

public class MyClass {

    @Autowired
    @LoadBalanced
    private RestTemplate restTemplate;

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

Now I want to access a service which needs OAuth2 authorization. I use a Keycloak server in order to provide it and Keycloak already provides an adapter with an specific KeycloakRestTemplate. Anyway, how to enhance it with load balancing?

Answer 1

We need to create a specific KeycloakRestTemplate which will use a LoadBalancerInterceptor:

@Configuration
@EnableWebSecurity
@ComponentScan(basePackageClasses = KeycloakSecurityComponents.class)
public class SecurityConfig extends KeycloakWebSecurityConfigurerAdapter {

    @Bean
    @Scope(ConfigurableBeanFactory.SCOPE_PROTOTYPE)
    @LoadBalanced
    public KeycloakRestTemplate keycloakRestTemplate(
            KeycloakClientRequestFactory keycloakClientRequestFactory,
            LoadBalancerInterceptor interceptor) {
        KeycloakRestTemplate result = new KeycloakRestTemplate(
            keycloakClientRequestFactory);
        // Add the interceptor for load balancing
        result.getInterceptors().add(interceptor);
        return result;
    }

    //More configurations for keycloak

}

So there's the chance of getting an Authorized / LoadBalanced template:

@Autowired
@LoadBalanced
protected KeycloakRestTemplate restTemplate;

See also:

• Add Ribbon load balancing to a vanilla RestTemplate