A showcase project for simple system in microservice architecture.
To Run prometheus:
docker compose upApi Gateway - Spring gateway with reactive router, Load Balancer, and Circuit Breaker.
To add circut breaker to gateway we use Resilience4j library
</dependency>
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-circuitbreaker-reactor-resilience4j</artifactId>
</dependency>Config:
@Configuration
public class GatewayConfig {
@Bean
public RouteLocator routeLocator(RouteLocatorBuilder routeLocatorBuilder) {
return routeLocatorBuilder
.routes()
.route("greetings", r -> r.path("/greetings/*")
.filters(f -> f.circuitBreaker(c -> c.setName("circut").setFallbackUri("forward:/fallback")))
.uri("lb://hello-service"))
.route("fallback", r -> r.path("/fallback").uri("lb://fallback-service"))
.build();
}Above config will set route to hello service, and if hello service will be unavailable, rerute request to fallback service
Discovery Service - Netflix Eureka.
Hello Service - Springboot application with simple message Hello.
In helllo serice we are using prometheus to count number of call to hello endpoint.
First we need to create Mettrics Manager
@Component
public class MetricsManager {
private final Counter counter;
public MetricsManager(MeterRegistry meterRegistry) {
this.counter = meterRegistry.counter("get_counter_functional");
}
public void inc(){
counter.increment();
}
}And now we can use it in our service:
@Bean
RouterFunction<ServerResponse> router() {
return route().nest(RequestPredicates.path("greetings"), builder -> builder.GET("/hello", h -> get())).build();
}
public Mono<ServerResponse> get() {
return Mono.fromRunnable(metricsManager::inc).subscribeOn(Schedulers.boundedElastic())
.then(ServerResponse.ok().bodyValue("Hello From service! " + value));
}Fallback Service - Springboot application that is used for Fallback in case Hello Service is not reacheble.