Distributed Tracing - Setup Zipkin and Sample Spring Boot Application

@RestController
@RequestMapping("/error-logs")
@RequiredArgsConstructor
@Slf4j

public class ErrorLogController {

    private final ErrorLogNotificationService errorLogNotificationService;

    private final RestTemplate restTemplate;

    @Value("${app.notification.url}")
    private String notificationUrl;


    @GetMapping("/notify")
    public int sendNotifications() {
        List<ErrorLogNotification> notifications = errorLogNotificationService.getAllErrorLogs();

        var targetUrl = notificationUrl + "/send";
        log.info("Sending notifications to {}", targetUrl);

        AtomicInteger atomicInteger = new AtomicInteger(0);

        notifications.forEach(notification -> {
            Boolean succeeded =
                    restTemplate.postForObject(targetUrl, notification, Boolean.class);

            if (Boolean.TRUE.equals(succeeded)) {
               atomicInteger.incrementAndGet();
            }

        });

        return atomicInteger.get();
    }
}

@RestController
@RequestMapping("/notifications")
@AllArgsConstructor
@Slf4j
public class NotificationController {

    private final NotificationSenderService notificationSenderService;

    @PostMapping("/send")
    public boolean sendNotification(@RequestBody ErrorLogNotification notification) {
        try {
            notificationSenderService.sendNotification(notification);
            return true;
        } catch (Exception e) {
            log.error("Error sending notification", e);
            return false;
        }
    }
}

plugins {
    java
    id("org.springframework.boot") version "3.3.2"
    id("io.spring.dependency-management") version "1.1.6"
}

group = "com.alexamy.nsa2.example"
version = "0.0.1-SNAPSHOT"

java {
    toolchain {
        languageVersion = JavaLanguageVersion.of(21)
    }
}

repositories {
    mavenCentral()
}

configurations {
    compileOnly {
        extendsFrom(configurations.annotationProcessor.get())
    }
}


dependencies {
    implementation("org.springframework.boot:spring-boot-starter-actuator")
    implementation("org.springframework.boot:spring-boot-starter-web")
    implementation("org.springframework.boot:spring-boot-starter-data-jpa")
    implementation("org.springframework.boot:spring-boot-starter-json")
    runtimeOnly("org.postgresql:postgresql")

    implementation("org.springframework.boot:spring-boot-starter-amqp")

    compileOnly("org.projectlombok:lombok")
    annotationProcessor("org.projectlombok:lombok")
    testAnnotationProcessor("org.projectlombok:lombok")

    implementation("org.mapstruct:mapstruct:1.5.5.Final")
    compileOnly ("org.mapstruct:mapstruct-processor:1.5.5.Final")
    annotationProcessor ("org.mapstruct:mapstruct-processor:1.5.5.Final")
    testAnnotationProcessor ("org.mapstruct:mapstruct-processor:1.5.5.Final")


    testImplementation("org.springframework.boot:spring-boot-starter-test")
    testRuntimeOnly("org.junit.platform:junit-platform-launcher")
}

tasks.withType<Test> {
    useJUnitPlatform()
}

spring.application.name: nsa2-opentelemetry-example

spring:
  main:
    banner-mode: off

  datasource:
    driver-class-name: org.postgresql.Driver
    url: jdbc:postgresql://${NSA2_DB_HOST:localhost}:${NSA2_DB_PORT:5432}/${NSA2_DB_NAME:nsa2}
    username: ${NSA2_DB_USERNAME:db-user}
    password: ${NSA2_DB_PASSWORD:db-password}


  rabbitmq:
    host: ${RABBITMQ_HOST:localhost}
    port: ${RABBITMQ_PORT:5672}
    username: ${RABBITMQ_USERNAME:user}
    password: ${RABBITMQ_PASSWORD:password}
    virtual-host: ${RABBITMQ_VHOST:nsa2}

app:
  notification:
    url: ${NOTIFICATION_URI:http://localhost:8080/notifications}

@Configuration
@AllArgsConstructor
public class RabbitConfig {
    public static final String EXCHANGE_NAME = "error-log-exchange";
    public static final String QUEUE_NAME = "error-log-queue";
    public static final String ROUTING_KEY = "error-log";

    private final ConnectionFactory connectionFactory;

    @Bean
    public RabbitTemplate rabbitTemplate() {
        final var rabbitTemplate = new RabbitTemplate(connectionFactory);

        rabbitTemplate.setBeanName("rabbitTemplate");
        rabbitTemplate.setMessageConverter(jackson2JsonMessageConverter());

        return rabbitTemplate;
    }

    @Bean
    public Jackson2JsonMessageConverter jackson2JsonMessageConverter() {
        return new Jackson2JsonMessageConverter();
    }

    @Bean
    public TopicExchange errorLogExchange() {
        return new TopicExchange(EXCHANGE_NAME);
    }

    @Bean
    Queue errorLogQueue() {
        return new Queue(QUEUE_NAME);
    }

    @Bean
    Binding declareBindingErrorLog() {
        return BindingBuilder.bind(errorLogQueue()).to(errorLogExchange()).with(ROUTING_KEY);
    }

}

@AllArgsConstructor
@Service
public class NotificationSenderServiceImpl implements NotificationSenderService {
    private final RabbitTemplate rabbitTemplate;

    @Override
    public void sendNotification(ErrorLogNotification errorLogNotification) {
        rabbitTemplate.convertAndSend(RabbitConfig.EXCHANGE_NAME, RabbitConfig.ROUTING_KEY, errorLogNotification);
    }

}

$ ./gradlew clean bootRun

$ curl http://localhost:8080/error-logs/notify

# it returns the number of notifications sent to the RabbitMQ server
4