Building a Simple Load Balancer with Spring Boot: A Step-by-Step Guide

In today's microservices architecture, load balancers play a crucial role in distributing traffic across multiple service instances. This article will walk you through building a simple yet functional load balancer using Spring Boot, complete with health checking and round-robin load distribution.

Project Overview

Our load balancer implementation consists of three main components:

1. 
   Load Balancer Service: The core component that handles request distribution


2. 
   API Service: Multiple instances of a demo service that will receive the distributed traffic


3. 
   Common Module: Shared DTOs and utilities

The complete project uses Spring Boot 3.2.0 and Java 21, showcasing modern Java features and enterprise-grade patterns.

Architecture

Here's a high-level view of our system architecture:

Remember that in production environments, you might want to use battle-tested solutions like Nginx, HAProxy, or cloud provider load balancers. However, understanding how load balancers work under the hood is valuable knowledge for any software engineer.