In this article I’m going to present an annotation-based Spring Boot library for integration with Istio. The Spring Boot Istio library provides auto-configuration, so you don’t have to do anything more than including it to your dependencies to be able to use it.
The library is using Istio Java Client me.snowdrop:istio-client
for communication with Istio API on Kubernetes. The following picture illustrates an architecture of presented solution on Kubernetes. The Spring Boot Istio is working just during application startup. It is able to modify existing Istio resources or creating new if there are no matching rules found.
Source code
The source code of library is available on my GitHub repository https://github.com/piomin/spring-boot-istio.git.
How to use it
To use in your Spring Boot application you include the following dependency.
<dependency> <groupId>com.github.piomin</groupId> <artifactId>spring-boot-istio</artifactId> <version>0.1.0.RELEASE</version> </dependency>
After that you should annotate one of your class with @EnableIstio
. The annotation contains several fields used for Istio DestinationRule
and VirtualService
objects.
@RestController @RequestMapping("/caller") @EnableIstio(version = "v1", timeout = 3, numberOfRetries = 3) public class CallerController { private static final Logger LOGGER = LoggerFactory.getLogger(CallerController.class); @Autowired BuildProperties buildProperties; @Autowired RestTemplate restTemplate; @Value("${VERSION}") private String version; @GetMapping("/ping") public String ping() { LOGGER.info("Ping: name={}, version={}", buildProperties.getName(), version); String response = restTemplate.getForObject("http://callme-service:8080/callme/ping", String.class); LOGGER.info("Calling: response={}", response); return "I'm caller-service " + version + ". Calling... " + response; } }
The name of Istio objects is generated basing on spring.application.name
. So you need to provide that name in your application.yml
.
spring: application: name: caller-service
Currently there are five available fields that may be used for @EnableIstio
.
@Target({ElementType.TYPE}) @Retention(RetentionPolicy.RUNTIME) @Documented public @interface EnableIstio { int timeout() default 0; String version() default ""; int weight() default 0; int numberOfRetries() default 0; int circuitBreakerErrors() default 0; }
Here’s the detailed description of available parameters.
version
– it indicates the version of IstioSubset
. We may define multiple versions of the same application. The name of label isversion
weight
– it sets a weight assigned to theSubset
indicated by theversion
labeltimeout
– a total read timeout in seconds on the client side – including retriesnumberOfRetries
– it enables retry mechanism. By default we are retrying all 5XX HTTP codes. The timeout of a single retry is calculated astimeout / numberOfRetries
circuitBreakerErrors
– it enables circuit breaker mechanism. It is based of a number of consecutive HTTP 5XX errors. If circuit is open for a single application it is ejected from the pool for 30 seconds
How it works
Here’s the Deployment
definition of our sample service. It should be labelled with the same version
as set inside @EnableIstio
.
apiVersion: apps/v1 kind: Deployment metadata: name: caller-service spec: replicas: 1 selector: matchLabels: app: caller-service template: metadata: name: caller-service labels: app: caller-service version: v1 spec: containers: - name: caller-service image: piomin/caller-service imagePullPolicy: IfNotPresent ports: - containerPort: 8080
Let’s deploy our sample application on Kubernetes. After deploy we may verify the status of Deployment
.
The name of created DestinationRule
is a concatenation of spring.application.name
property value and word -destination
.
The name of created VirtualService
is a concatenation of spring.application.name
property value and word -route
. Here’s the definition of VirtualService
created for annotation @EnableIstio(version = "v1", timeout = 3, numberOfRetries = 3)
and caller-service
application.
How it is implemented
We need to define bean that implements BeanPostProcessor
interface. On application startup it is trying to find the annotation @EnableIstio
. If such annotation exists it takes a value of its fields and then it is creating new Istio objects or editing the currently existing objects.
public class EnableIstioAnnotationProcessor implements BeanPostProcessor { private final Logger LOGGER = LoggerFactory.getLogger(EnableIstioAnnotationProcessor.class); private ConfigurableListableBeanFactory configurableBeanFactory; private IstioClient istioClient; private IstioService istioService; public EnableIstioAnnotationProcessor(ConfigurableListableBeanFactory configurableBeanFactory, IstioClient istioClient, IstioService istioService) { this.configurableBeanFactory = configurableBeanFactory; this.istioClient = istioClient; this.istioService = istioService; } public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException { EnableIstio enableIstioAnnotation = bean.getClass().getAnnotation(EnableIstio.class); if (enableIstioAnnotation != null) { LOGGER.info("Istio feature enabled: {}", enableIstioAnnotation); Resource<DestinationRule, DoneableDestinationRule> resource = istioClient.v1beta1DestinationRule() .withName(istioService.getDestinationRuleName()); if (resource.get() == null) { createNewDestinationRule(enableIstioAnnotation); } else { editDestinationRule(enableIstioAnnotation, resource); } Resource<VirtualService, DoneableVirtualService> resource2 = istioClient.v1beta1VirtualService() .withName(istioService.getVirtualServiceName()); if (resource2.get() == null) { createNewVirtualService(enableIstioAnnotation); } else { editVirtualService(enableIstioAnnotation, resource2); } } return bean; } }
We are using API provided by Istio Client library. It provides a set of builders dedicated for creating elements of Istio objects.
private void createNewDestinationRule(EnableIstio enableIstioAnnotation) { DestinationRule dr = new DestinationRuleBuilder() .withMetadata(istioService.buildDestinationRuleMetadata()) .withNewSpec() .withNewHost(istioService.getApplicationName()) .withSubsets(istioService.buildSubset(enableIstioAnnotation)) .withTrafficPolicy(istioService.buildCircuitBreaker(enableIstioAnnotation)) .endSpec() .build(); istioClient.v1beta1DestinationRule().create(dr); LOGGER.info("New DestinationRule created: {}", dr); } private void editDestinationRule(EnableIstio enableIstioAnnotation, Resource<DestinationRule, DoneableDestinationRule> resource) { LOGGER.info("Found DestinationRule: {}", resource.get()); if (!enableIstioAnnotation.version().isEmpty()) { Optional<Subset> subset = resource.get().getSpec().getSubsets().stream() .filter(s -> s.getName().equals(enableIstioAnnotation.version())) .findAny(); resource.edit() .editSpec() .addAllToSubsets(subset.isEmpty() ? List.of(istioService.buildSubset(enableIstioAnnotation)) : Collections.emptyList()) .editOrNewTrafficPolicyLike(istioService.buildCircuitBreaker(enableIstioAnnotation)).endTrafficPolicy() .endSpec() .done(); } } private void createNewVirtualService(EnableIstio enableIstioAnnotation) { VirtualService vs = new VirtualServiceBuilder() .withNewMetadata().withName(istioService.getVirtualServiceName()).endMetadata() .withNewSpec() .addToHosts(istioService.getApplicationName()) .addNewHttp() .withTimeout(enableIstioAnnotation.timeout() == 0 ? null : new Duration(0, (long) enableIstioAnnotation.timeout())) .withRetries(istioService.buildRetry(enableIstioAnnotation)) .addNewRoute().withNewDestinationLike(istioService.buildDestination(enableIstioAnnotation)).endDestination().endRoute() .endHttp() .endSpec() .build(); istioClient.v1beta1VirtualService().create(vs); LOGGER.info("New VirtualService created: {}", vs); } private void editVirtualService(EnableIstio enableIstioAnnotation, Resource<VirtualService, DoneableVirtualService> resource) { LOGGER.info("Found VirtualService: {}", resource.get()); if (!enableIstioAnnotation.version().isEmpty()) { istioClient.v1beta1VirtualService().withName(istioService.getVirtualServiceName()) .edit() .editSpec() .editFirstHttp() .withTimeout(enableIstioAnnotation.timeout() == 0 ? null : new Duration(0, (long) enableIstioAnnotation.timeout())) .withRetries(istioService.buildRetry(enableIstioAnnotation)) .editFirstRoute() .withWeight(enableIstioAnnotation.weight() == 0 ? null: enableIstioAnnotation.weight()) .editOrNewDestinationLike(istioService.buildDestination(enableIstioAnnotation)).endDestination() .endRoute() .endHttp() .endSpec() .done(); } }