Spring Boot 3 Demo Tracing with Jaeger

A simple Spring Boot 3 multi-module project with OpenTelemetry, Jaeger, and Prometheus for observability. 0 comments
By Sopheaktra Eang | May 27, 2025

🌟 Observability in a Simple Multi-Module Spring Boot 3 App

Most observability tutorials focus on microservices or heavy Domain-Driven Design (DDD) projects. But what if you're just working on a simple multi-module Spring Boot 3 application?

Good news: you can still integrate tracing and metrics like a pro.

In this post, I’ll walk you through how I built a simple, standalone Spring Boot 3 project with:

  • ✅ Gradle multi-module setup

  • ✅ OpenTelemetry for distributed tracing

  • ✅ Jaeger to visualize traces

  • ✅ Prometheus + Micrometer for metrics

  • ✅ Docker Compose to run the full observability stack locally

🔧 Why Multi-Module?

Multi-module projects in Gradle help with:

  • Separation of concerns (e.g., separating web, core logic, and config)

  • Faster builds

  • Better organization for growing projects

This project has basic modules like:

  • client-consumer – for handle consume api, webClient for external and internal api.

  • logging – handle log4j2 for service need logging.

  • service-a & service-b – testing service

  • tracing – tracing and metrics setup for base module

📦 Project Setup

Clone the Repo

git clone https://github.com/Tra22/spring-boot-3-demo-tracing.git 
cd spring-boot-3-demo-tracing

This starts:

🔍 Tracing with OpenTelemetry

OpenTelemetry is added via the Java agent. It automatically traces:

  • Incoming HTTP requests

  • Spring controllers

  • Any custom spans you define

Jaeger helps you visualize the trace flow, even within a single app.

📊 Metrics with Prometheus + Micrometer

Spring Boot 3 uses Micrometer to expose JVM and request metrics via:

service-a: http://localhost:8080/actuator/prometheus
service-b: http://localhost:8081/actuator/prometheus

Prometheus scrapes this and lets you query:

  • http_server_requests_seconds_count

  • jvm_memory_used_bytes

  • system_cpu_usage

💡 Key Benefits

  • No microservices needed

  • Simple Gradle multi-module setup

  • Visibility into your app's behavior

  • Easily portable to production or cloud environments

🔗 Repo

🧰 Code: github.com/Tra22/spring-boot-3-demo-tracing

🏁 Wrap-Up

If you're building a Spring Boot app and want clean code and observability without the complexity of DDD or microservices, this approach gives you the best of both worlds.

You’ll get:

  • A better understanding of your system

  • Easier performance debugging

  • A strong foundation for future growth

✅ Give the repo a ⭐ on GitHub if you found it useful.
🛠️ Feel free to fork it and customize for your own projects.