Spring Cloud discovery for multiple service versions

Question

I'm asking myself a question without finding responses for it. Maybe someone here would have ideas about that ;-) Using a services registry (Eureka) in Spring Cloud with RestTemplate and Feign clients, I have different build versions of the same service. The build version being documented through Actuator's /info endpoint.

{
"build": {
"version": "0.0.1-SNAPSHOT",
"artifact": "service-a",
"name": "service-a",
"group": "com.mycompany",
"time": 1487253409000
}
}
...
{
"build": {
"version": "0.0.2-SNAPSHOT",
"artifact": "service-a",
"name": "service-a",
"group": "com.mycompany",
"time": 1487325340000
}
}

Is there any mean to ask for a particular build version at client's call? Should I use gateway's routing filters in order to manage that? But the version detection would remain an issue I guess...

Well, any suggestion appreciated.

Answer 1

Ok. This is the code to inject the build version into the service ("service-a") instance metadata to be registered by Eureka:

@Configuration
@ConditionalOnClass({ EurekaInstanceConfigBean.class, EurekaClient.class })
public class EurekaClientInstanceBuildVersionAutoConfiguration {

    @Autowired(required = false)
    private EurekaInstanceConfig instanceConfig;

    @Autowired(required = false)
    private BuildProperties buildProperties;

    @Value("${eureka.instance.metadata.keys.version:instanceBuildVersion}")
    private String versionMetadataKey;

    @PostConstruct
    public void init() {
        if (this.instanceConfig == null || buildProperties == null) {
            return;
        }
        this.instanceConfig.getMetadataMap().put(versionMetadataKey, buildProperties.getVersion());
    }
}

This is the code to validate metadata transmission within a "service-b":

@Component
public class DiscoveryClientRunner implements CommandLineRunner {
    private final Logger logger = LoggerFactory.getLogger(this.getClass());

    @Autowired
    private DiscoveryClient client;

    @Override
    public void run(String... args) throws Exception {
        client.getInstances("service-a").forEach((ServiceInstance s) -> {
            logger.debug(String.format("%s: %s", s.getServiceId(), s.getUri()));
            for (Entry<String, String> md : s.getMetadata().entrySet()) {
                logger.debug(String.format("%s: %s", md.getKey(), md.getValue()));
            }
        });
    }
}

Notice that if "dashed composed" (i.e. "instance-build-version"), the metadata key is Camel Case forced.

And this is the solution I found to filter service instances according to their version:

@Configuration
@EnableConfigurationProperties(InstanceBuildVersionProperties.class)
public class EurekaInstanceBuildVersionFilterAutoConfig {

    @Value("${eureka.instance.metadata.keys.version:instanceBuildVersion}")
    private String versionMetadataKey;

    @Bean
    @ConditionalOnProperty(name = "eureka.client.filter.enabled", havingValue = "true")
    public EurekaInstanceBuildVersionFilter eurekaInstanceBuildVersionFilter(InstanceBuildVersionProperties filters) {
        return new EurekaInstanceBuildVersionFilter(versionMetadataKey, filters);
    }
}

@Aspect
@RequiredArgsConstructor
public class EurekaInstanceBuildVersionFilter {
    private final Logger logger = LoggerFactory.getLogger(this.getClass());

    private final String versionMetadataKey;
    private final InstanceBuildVersionProperties filters;

    @SuppressWarnings("unchecked")
    @Around("execution(public * org.springframework.cloud.netflix.eureka.EurekaDiscoveryClient.getInstances(..))")
    public Object filterInstances(ProceedingJoinPoint jp) throws Throwable {
        if (filters == null || !filters.isEnabled()) logger.error("Should not be filtering...");
        List<ServiceInstance> instances = (List<ServiceInstance>) jp.proceed();
        return instances.stream()
                .filter(i -> filters.isKept((String) jp.getArgs()[0], i.getMetadata().get(versionMetadataKey))) //DEBUG MD key is Camel Cased!
                .collect(Collectors.toList());
    }
}

@ConfigurationProperties("eureka.client.filter")
public class InstanceBuildVersionProperties {
    private final Logger logger = LoggerFactory.getLogger(this.getClass());

    /**
     * Indicates whether or not service instances versions should be filtered
     */
    @Getter @Setter
    private boolean enabled = false;

    /**
     * Map of service instance version filters.
     * The key is the service name and the value configures a filter set for services instances
     */
    @Getter
    private Map<String, InstanceBuildVersionFilter> services = new HashMap<>();

    public boolean isKept(String serviceId, String instanceVersion) {
        logger.debug("Considering service {} instance version {}", serviceId, instanceVersion);
        if (services.containsKey(serviceId) && StringUtils.hasText(instanceVersion)) {
            InstanceBuildVersionFilter filter = services.get(serviceId);
            String[] filteredVersions = filter.getVersions().split("\\s*,\\s*");    // trimming
            logger.debug((filter.isExcludeVersions() ? "Excluding" : "Including") + " instances: " + Arrays.toString(filteredVersions));
            return contains(filteredVersions, instanceVersion) ? !filter.isExcludeVersions() : filter.isExcludeVersions();
        }
        return true;
    }

    @Getter @Setter
    public static class InstanceBuildVersionFilter {
        /**
         * Comma separated list of service version labels to filter
         */
        private String versions;
        /**
         * Indicates whether or not to keep the associated instance versions.
         * When false, versions are kept, otherwise they will be filtered out
         */
        private boolean excludeVersions = false;
    }
}

You can specify for every consumed service a list of expected or avoided versions and the discovery will be filtered accordingly.

logging.level.com.mycompany.demo=DEBUG

eureka.client.filter.enabled=true

eureka.client.filter.services.service-a.versions=0.0.1-SNAPSHOT

Please submit as comments any suggestion. Thx

Answer 2

Service 1 registers v1 and v2 with Eureka

Service 2 discovers and sends requests to Service 1's v1 and v2 using different Ribbon clients

I got this demo to work and will blog about it in the next couple of days.

http://tech.asimio.net/2017/03/06/Multi-version-Service-Discovery-using-Spring-Cloud-Netflix-Eureka-and-Ribbon.html

The idea I followed was for RestTemplate to use a different Ribbon client for each version because each client has its own ServerListFilter.

---

Service 1

application.yml

...
eureka:
  client:
    registerWithEureka: true
    fetchRegistry: true
    serviceUrl:
      defaultZone: http://localhost:8000/eureka/
  instance:
    hostname: ${hostName}
    statusPageUrlPath: ${management.context-path}/info
    healthCheckUrlPath: ${management.context-path}/health
    preferIpAddress: true
    metadataMap:
      instanceId: ${spring.application.name}:${server.port}

---
spring:
   profiles: v1
eureka:
  instance:
    metadataMap:
      versions: v1

---
spring:
   profiles: v1v2
eureka:
  instance:
    metadataMap:
      versions: v1,v2
...

---

Service 2

application.yml

...
eureka:
  client:
    registerWithEureka: false
    fetchRegistry: true
    serviceUrl:
      defaultZone: http://localhost:8000/eureka/

demo-multiversion-registration-api-1-v1:
   ribbon:
     # Eureka vipAddress of the target service
     DeploymentContextBasedVipAddresses: demo-multiversion-registration-api-1
     NIWSServerListClassName: com.netflix.niws.loadbalancer.DiscoveryEnabledNIWSServerList
     # Interval to refresh the server list from the source (ms)
     ServerListRefreshInterval: 30000

demo-multiversion-registration-api-1-v2:
   ribbon:
     # Eureka vipAddress of the target service
     DeploymentContextBasedVipAddresses: demo-multiversion-registration-api-1
     NIWSServerListClassName: com.netflix.niws.loadbalancer.DiscoveryEnabledNIWSServerList
     # Interval to refresh the server list from the source (ms)
     ServerListRefreshInterval: 30000
...

Application.java

...
@SpringBootApplication(scanBasePackages = {
    "com.asimio.api.multiversion.demo2.config",
    "com.asimio.api.multiversion.demo2.rest"
})
@EnableDiscoveryClient
public class Application {

    public static void main(String[] args) {
        SpringApplication.run(Application.class, args);
    }
}

AppConfig.java (See how the Ribbon client name matches the Ribbon key found in application.yml

...
@Configuration
@RibbonClients(value = {
    @RibbonClient(name = "demo-multiversion-registration-api-1-v1", configuration = RibbonConfigDemoApi1V1.class),
    @RibbonClient(name = "demo-multiversion-registration-api-1-v2", configuration = RibbonConfigDemoApi1V2.class)
})
public class AppConfig {

    @Bean(name = "loadBalancedRestTemplate")
    @LoadBalanced
    public RestTemplate loadBalancedRestTemplate() {
        return new RestTemplate();
    }
}

RibbonConfigDemoApi1V1.java

...
public class RibbonConfigDemoApi1V1 {

    private DiscoveryClient discoveryClient;

    @Bean
    public ServerListFilter<Server> serverListFilter() {
        return new VersionedNIWSServerListFilter<>(this.discoveryClient, RibbonClientApi.DEMO_REGISTRATION_API_1_V1);
    }

    @Autowired
    public void setDiscoveryClient(DiscoveryClient discoveryClient) {
        this.discoveryClient = discoveryClient;
    }
}

RibbonConfigDemoApi1V2.java is similar but using RibbonClientApi.DEMO_REGISTRATION_API_1_V2

RibbonClientApi.java

...
public enum RibbonClientApi {

    DEMO_REGISTRATION_API_1_V1("demo-multiversion-registration-api-1", "v1"),

    DEMO_REGISTRATION_API_1_V2("demo-multiversion-registration-api-1", "v2");

    public final String serviceId;
    public final String version;

    private RibbonClientApi(String serviceId, String version) {
        this.serviceId = serviceId;
        this.version = version;
    }
}

VersionedNIWSServerListFilter.java

...
public class VersionedNIWSServerListFilter<T extends Server> extends DefaultNIWSServerListFilter<T> {

    private static final String VERSION_KEY = "versions";

    private final DiscoveryClient discoveryClient;
    private final RibbonClientApi ribbonClientApi;

    public VersionedNIWSServerListFilter(DiscoveryClient discoveryClient, RibbonClientApi ribbonClientApi) {
        this.discoveryClient = discoveryClient;
        this.ribbonClientApi = ribbonClientApi;
    }

    @Override
    public List<T> getFilteredListOfServers(List<T> servers) {
        List<T> result = new ArrayList<>();
        List<ServiceInstance> serviceInstances = this.discoveryClient.getInstances(this.ribbonClientApi.serviceId);
        for (ServiceInstance serviceInstance : serviceInstances) {
            List<String> versions = this.getInstanceVersions(serviceInstance);
            if (versions.isEmpty() || versions.contains(this.ribbonClientApi.version)) {
                result.addAll(this.findServerForVersion(servers, serviceInstance));
            }
        }
        return result;
    }

    private List<String> getInstanceVersions(ServiceInstance serviceInstance) {
        List<String> result = new ArrayList<>();
        String rawVersions = serviceInstance.getMetadata().get(VERSION_KEY);
        if (StringUtils.isNotBlank(rawVersions)) {
            result.addAll(Arrays.asList(rawVersions.split(",")));
        }
        return result;
    }
...

AggregationResource.java

...
@RestController
@RequestMapping(value = "/aggregation", produces = "application/json")
public class AggregationResource {

    private static final String ACTORS_SERVICE_ID_V1 = "demo-multiversion-registration-api-1-v1";
    private static final String ACTORS_SERVICE_ID_V2 = "demo-multiversion-registration-api-1-v2";

    private RestTemplate loadBalancedRestTemplate;

    @RequestMapping(value = "/v1/actors/{id}", method = RequestMethod.GET)
    public com.asimio.api.multiversion.demo2.model.v1.Actor findActorV1(@PathVariable(value = "id") String id) {
        String url = String.format("http://%s/v1/actors/{id}", ACTORS_SERVICE_ID_V1);
        return this.loadBalancedRestTemplate.getForObject(url, com.asimio.api.multiversion.demo2.model.v1.Actor.class, id);
    }

    @RequestMapping(value = "/v2/actors/{id}", method = RequestMethod.GET)
    public com.asimio.api.multiversion.demo2.model.v2.Actor findActorV2(@PathVariable(value = "id") String id) {
        String url = String.format("http://%s/v2/actors/{id}", ACTORS_SERVICE_ID_V2);
        return this.loadBalancedRestTemplate.getForObject(url, com.asimio.api.multiversion.demo2.model.v2.Actor.class, id);
    }

    @Autowired
    public void setLoadBalancedRestTemplate(RestTemplate loadBalancedRestTemplate) {
        this.loadBalancedRestTemplate = loadBalancedRestTemplate;
    }
}